Introduction

Wearable and implantable biosensors have emerged as a prominent field of research in recent years, which provide access to physiological signals and are of great significance for the diagnosis and treatment of diseases1. Ongoing advancements in medicine and healthcare have led to widespread applications of these devices, primarily in health monitoring2,3,4,5,6,7, postoperative evaluation8,9,10, drug delivery11,12 and more. For instance, smart wearable devices can effectively monitor various physiological parameters, such as heart rate13, blood pressure14 and body temperature15. Given that wearable devices need to be worn without disrupting the wearer’s daily life, there is a requirement for miniaturization and flexibility. In addition, implantable devices requiring surgical implantation must minimize discomfort and ensure robust biocompatibility to prevent adverse reactions such as inflammation or immune responses.

Traditional sensors often rely on wire-connections or batteries for power supply, which not only limits their miniaturization and flexibility, but also can pose a potential risk of infection, consequently restricting their applications in wearable and implantable scenarios16. To address these limitations, wireless data transmission technology such as Near Field Communication /Radio Frequency Identification (NFC/RFID) emerges as a promising solution. NFC is a short-range wireless technology designed for near-field interactions (typically less than 10 cm), supporting bidirectional data transmission and encryption protocols for high security17,18. It is commonly adopted in high-security applications such as mobile payments and smart device pairing. In comparison, RFID operates across low-frequency (LF, 30 kHz-300 kHz), high-frequency (HF, 3 MHz-30 MHz), and ultra-high-frequency (UHF, 300 MHz-3 GHz) bands, with communication distances ranging from near-field (centimeter-level) to far-field (tens of meters). It primarily enables unidirectional data collection through low-cost passive tags, making it ideal for logistics tracking, warehouse management, and access control.

Building upon these capabilities, NFC/RFID technologies offer distinct advantages for wearable and implantable devices that demand both miniaturization and flexibility19,20. The first notable characteristic of NFC/RFID technology is its support for wireless power and data transmission21. NFC systems and specific RFID implementations (such as short-range applications at 13.56 MHz) employ inductive electromagnetic coupling between antennas to achieve power transfer and data communication, whereas RFID systems operating at UHF bands or intended for extended-range operation rely on far-field electromagnetic wave propagation. This wireless transmission capability of NFC/RFID systems eliminate the requirement for batteries or physical electrical connections of sensors. The second is direct sensing capabilities: NFC/RFID antennas can be modified for direct sensing, offering unique benefits by integrating data transmission and sensing modules. Thirdly, this technology ensures rapid data exchange and enhanced security. Information exchange through NFC/RFID technology typically occurs in under 0.1 seconds17, enabling rapid acquisition of patient physiological data. The secure communication protocols further protect sensitive patients’ data during transmission. Last but not least is the adaptability to achieve flexibility and biocompatibility. Specific designs like serpentine structures18 and 3D helical structures22, along with materials such as silver nanowires2 and MXene23, could enhance the flexibility of NFC/RFID antennas, exerting no extra mechanical stiffness for biomedical systems. Antennas fabricated from bioabsorbable materials further enhance their suitability for implantable biomedical applications8.

Taken together, these advantages have drawn increasing attention to NFC/RFID systems as enabling technologies for next-generation wearable and implantable biomedical devices, spurring comprehensive reviews in this interdisciplinary field. However, existing reviews typically focus on sensor materials, design principles, sensing mechanisms, and application scenarios24,25,26,27. Antennas, despite being crucial elements of wireless systems, often receive only cursory attention regarding their contributions to sensor or drug delivery functionality28,29. To address this gap, our review explores the specific design requirements and working mechanisms of antennas for wearable and implantable applications. We provide a comprehensive summary and evaluation of flexible NFC/RFID-based sensors/systems (i.e., sensors/systems that utilize NFC or RFID modules for wireless communication and/or power transfer, or directly employ antenna structures as sensing elements) for medical applications (Table 1), offering valuable insights for researchers and practitioners in this field.

Table 1 Comparison of recent advances in NFC/RFID-based biomedical applications
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This review is structured as follows (Fig. 1): requirements and design mechanisms of NFC/RFID antennas in wearable and implantable contexts, recent advancements in NFC/RFID-based physical and bio/chemical sensors for physiological health monitoring, emerging NFC/RFID-based implantable drug delivery systems, and existing challenges as well as future research directions. Antenna design forms the foundation of all wireless communication in following advanced functional systems and is therefore expected to be addressed first. Physical and bio/chemical sensors represent the two major sensing paradigms that enable data collection from the human body, with distinct design considerations and applications. Finally, drug delivery systems represent the advanced intervention capabilities that complete the sensing-to-treatment pipeline. This organizational approach allows us to examine both the enabling technology (antenna designing) and their applications (sensing and therapeutic delivery) in a logical progression from fundamental components to integrated systems. By focusing on these key areas, we aim to provide a thorough analysis of current researches in this interdisciplinary field, highlighting the cooperation of antenna design with flexible materials and soft devices in advancing wearables and implants.

Fig. 1
figure 1

Illustration of general flexible NFC/RFID-based sensing systems for wearable and implantable biomedical applications, including antenna design8,37, Copyright 2019, Springer Nature, Copyright 2021, IEEE; physical sensors38,52, Copyright 2019, Springer Nature, Copyright 2022, ACS; bio/chemical sensors84,131, Copyright 2018, ACS, Copyright 2023, Elsevier; and drug delivery systems122,129, Copyright 2024, Springer Nature, Copyright 2020, AAAS

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The requirements and design mechanisms of NFC/RFID antenna circuit

NFC/RFID-based communication systems synergistically integrate sensing and wireless power transfer through electromagnetic coupling between a reader antenna and a passive tag antenna, forming a distributed RLC resonant network where paired antennas (mostly in coil forms) establish mutual inductance.

In sensing mode, the tag antenna embeds environment-responsive components that modulate its equivalent circuit parameters (R、L or C) proportionally to external stimuli such as temperature or pressure. This parametric variation induces quantifiable resonant frequency deviations that are captured through mutual coupling by the reader antenna, and these deviations can then be demodulated into quantized sensor data.

In wireless power transfer mode, optimized power transfer is achieved through mutual coupling between the reader and the tag, where the tag-integrated energy harvesting circuitry converts induced AC power into regulated DC output with dynamic impedance matching ensuring continuous energy delivery for battery-less sensors and embedded microcontrollers.

In the implantable and wearable applications of NFC/RFID antenna, not only strict performance standards need to be satisfied, but also safety and comfort issues in practical use should be considered. These challenges have led to increasing research efforts focused on optimizing NFC/RFID antenna designs for implantable and wearable applications. To this end, we will first summarize the key requirements that NFC/RFID antennas must fulfill in implantable and wearable scenarios, followed by an analysis of design strategies tailored to meet these requirements.

Specific requirements for implantable or wearable applications

The NFC/RFID-based communication system consists of a reader and a tag. NFC/RFID tag antennas significantly impact the quality of near-field communication. Given their unique operating environments, such as curved body surfaces or deep tissues in vivo, properties like miniaturization, high transmission efficiency, flexibility, biocompatibility and biodegradability are essential for user comfort, effective signal collection, and biosafety.

Miniaturization

Given that strict size and weight limitations are necessary for human comfort, antenna miniaturization is a consistent requirement in biomedical applications. The miniaturization of antennas is limited by the operating frequency’s wavelength and energy transmission efficiency. It is known that the antenna size is proportional to its operation wavelength, and for commonly adopted NFC/RFID bands, the operation wavelengths are considerably long (For instance, the Industrial Scientific Medical band at 2.45 GHz corresponds to a free-space wavelength of 122 mm). Although the high permittivity of human tissue can significantly reduce antenna size, it also considerably degrades transmission efficiency. Additionally, studies have shown that higher frequencies result in greater energy absorption, further reducing energy transmission efficiency. Therefore, it is essential to strike a balance between antenna miniaturization and transmission efficiency.

Coil antennas serve as the fundamental components in NFC and HF RFID systems operating at 13.56 MHz, achieving remarkable miniaturization despite the low operating frequency (free-space wavelength ~22 m)30. This miniaturization is enabled by tightly coupled multi-turn spiral configurations, where the cumulative conductor length generates substantial distributed inductance, while the inter-turn capacitive coupling introduces effective capacitance. Through strategic optimization of turn count, conductor width, and inter-turn spacing, coil antennas achieve self-resonance at target frequencies with sub-wavelength physical dimensions. However, it should be noted that the values of inductance and capacitance would affect the power transmission efficiency between the reader and the tag as they determine the resonant characteristics and impedance matching of the system. Therefore, miniaturization and transmission efficiency should be balanced adequately during the design31.

Transmission efficiency

The NFC antennas are usually used to realize data exchange from different devices, or energy transmission to power sensors and electronic circuits. Thus, to ensure the transmission quality, the high transmission efficiency of NFC antennas is essential. Typically, NFC antennas can achieve a transmission efficiency of 70-90% through inductive coupling technology, and the efficiency decreases when the separation distance between two antennas increases. It should be noted that there are two factors that would affect the antenna efficiency: the properties of the conductor and substrate, and the alignment between the two NFC antennas. For the former, materials with higher conductivity and substrates with lower loss tangents are preferred to achieve high transmission efficiency. However, while traditional structures based on copper and solid PCBs exhibit low loss characteristics, they often fail to meet the requirements for flexibility and stretchability. Regarding the latter, optimal efficiency is achieved only when two NFC antennas are positioned parallel with their axes precisely aligned32,33. Any deviation from this alignment can lead to substantial variations in the mutual inductance coefficient, thereby negatively impacting transmission efficiency. Since achieving perfect alignment is often impractical, recent advancements have focused on mitigating this limitation. For instance, ferrite-backed antennas have been adopted to broaden the magnetic field distribution, thereby enhancing radiation efficiency34. Additionally, integrating rectifiers with supercapacitors has been explored to achieve a synergistic balance between energy storage and transmission. Despite these solutions, maintaining high efficiency in realistic scenarios still remains a challenge35.

Flexibility/stretchability

Traditional commercial NFC tag antennas, such as NFC coils, are typically established on a rigid PCBs etched with copper36, with rigid sensors and hard electronic components integrated on them. However, these rigid designs lack flexibility and could cause discomfort for the human body. More importantly, they are susceptible to fractures, which limits the application of NFC-based wearable sensor devices. Therefore, there is a preference for stretchable sensors and flexible electronic components constructed from materials like PDMS, PET, and other intrinsically flexible materials. For instance, PDMS is employed in the fabrication of smart wound dressings capable of continuous temperature monitoring37, while SEBS-based stretchable sensors can be seamlessly integrated with human skin to acquire both physiological parameters and motion-related signals38. These materials are chosen for their ease of bending, excellent electromagnetic properties, and high thermal and chemical stability. Alternatively, stretchable liquid conductors like Eutectic Gallium Indium (EGaIn) are adopted to replace traditional copper conductors. However, the high cost of these liquid conductors limits their suitability for large-scale manufacturing30. Additionally, the interface between rigid electronic components and stretchable materials tends to be relatively weak, and fully flexible electronic components have not yet been developed38. Thus, achieving a completely soft, comfortable, and stretchable NFC-based sensor system remains a major challenge.

Material biocompatibility/biodegradability

For NFC/RFID-based implantable sensors exposed to human tissues, the biocompatibility and biodegradability of the materials are crucial considerations. Biocompatible materials can be in direct contact with human tissues without eliciting an immune response39, which ensures no occurrence of significant adverse reactions and maintains patient safety. While biodegradable materials can be absorbed or excreted by the human body under natural or chemically induced conditions once the operational lifespan of the implanted devices concludes40. This characteristic eliminates the need for secondary surgery to remove the devices, thereby reducing potential risks to patients.

Antenna as a sensing element

It is known that antennas can be regarded as LC resonators and their resonant performance—resonant frequencies, reflection coefficient, and input impedance—varies with changes in structure parameters as well as the working environment. Consequently, antennas can be utilized as the sensor elements, with their performance reflecting variations in the target. Unlike systems that merely use NFC/RFID technology for sensor data transmission, those equipped with NFC/RFID-based antenna sensors utilize the antenna itself as the sensing element, which enables higher integration and miniaturization. Currently, antennas adopted as sensors can be separated into two categories: microstrip patch antenna sensors and passive LC resonant sensors.

Microstrip patch antenna sensor

Figure 2a illustrates a typical microstrip patch antenna designed for far field radiation, consisting of three components, a rectangular metal patch on the top, a metal ground at bottom and a dielectric substrate in between41. The thickness of the substrate (h) is much smaller than the free-space wavelength (λ0), typically in the range of 0.003λ0 to 0.05λ0. For a rectangular patch, its length L is usually within the range λ0/3 < L < λ0/2, and the typical electric field lines are shown in Fig. 2b. As can be seen, most of the electric field lines are concentrated within the substrate, with only a few extending into the air. When W/h ≫ 1, the electric field lines are primarily confined to the substrate. The fringing effect causes the microstrip patch to appear electrically larger than its physical dimensions. As demonstrated in Fig. 2c, a rectangular microstrip patch antenna can be modeled as an array of two narrow radiating slots, each with width W and height h, separated by a distance L. Basically, the transmission-line model represents the microstrip antenna as two slots separated by a low-impedance transmission line of length L.

Fig. 2: Design mechanisms of NFC/RFID antenna circuit.
figure 2

a Geometry of rectangular microstrip patch antenna. b Electric field line distribution in the side view of a rectangular microstrip patch antenna. c Top view of rectangular microstrip patch antenna. d Equivalent circuit of a LC resonant sensor132,133. Copyright 2021, IEEE; Copyright 2015, MDPI. e Equivalent circuit of the NFC wireless power transfer system. f Geometric shapes of planar spiral coil for energy transmission. g Geometric shape and side view of planar rectangular coil for energy transmission

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Due to edge effects, the electrical length of the patch exceeds its physical length L, necessitating a compensation length \(\varDelta L\) to accurately calculate its resonant frequency:

$$\varDelta L=0.412h\frac{\left({\varepsilon }_{e}+0.3\right)\left(\frac{W}{h}+0.264\right)}{({\varepsilon }_{e}-0.258)\left(\frac{W}{h}+0.8\right)}$$
(2-1)
$${\varepsilon }_{e}=\frac{{\varepsilon }_{r}+1}{2}+\frac{{\varepsilon }_{r}-1}{2}{\left(1+12\frac{h}{W}\right)}^{-\frac{1}{2}}$$
(2-2)

where εr and εe are the relative and effective dielectric constants of the dielectric substrate, respectively, h denotes the substrate height, and W indicates the width of the rectangular patch. Consequently, the relationship between the patch dimensions and the required resonant frequency f can be expressed as

$$L=\frac{c}{2f\sqrt{{\varepsilon }_{e}}}-2\varDelta L$$
(2-3)
$$W=\frac{c}{2f}{\left(\frac{{\varepsilon }_{r}+1}{2}\right)}^{-\frac{1}{2}}$$
(2-4)

where \(c\) is the speed of light.

It can be concluded from these equations that the resonant frequency f of the antenna sensor is affected by the dimensions of the rectangular microstrip patch (W and L) and the properties of the dielectric substrate (h and εr). Thus, various sensors have been developed accordingly. For instance, a passive wireless strain sensor based on microstrip patch antenna has been proposed, where shifts in resonant frequency occur in response to the patch’s deformation42. Moreover, a frequency-agile microstrip patch antenna has been established on a ferroelectric substrate composed of barium strontium titanate (BaxSr1-xTiO3), achieving frequency agility through alterations in the dielectric constant of the substrate (εr)43.

Passive LC resonant sensor

As illustrated in Fig. 2d, a typical LC resonant passive sensor can be modeled as a serial LCR resonant circuit, which consists of three fundamental components, inductors (Ls), capacitors (Cs), and parasitic resistors (Rs). These elements collectively determine the resonant characteristics of the sensor, where its resonant frequency fs and quality factor (Qs) can be calculated as:

$${f}_{s}=\frac{1}{2\pi \sqrt{{L}_{s}{C}_{s}}}$$
(2-5)
$${Q}_{s}=\frac{1}{{R}_{s}}\sqrt{\frac{{L}_{s}}{{C}_{s}}}$$
(2-6)

It can be concluded from Eqs. (2-5) and (2-6) that fs and Qs are directly influenced by Ls, Cs and Rs. Consequently, Rs, Ls and Cs can serve as sensitive components for LC sensors, with Zs representing its equivalent input impedance.

The reading coil can be equivalent to an inductor (L0) and a parasitic resistor (R0), and the coupling strength between the sensor inductors Ls and reader inductor L0 is represented by M. Therefore, the equivalent input impedance for a reading coil coupled with an LC sensor can be written as:

$${Z}_{\text{in}}={R}_{0}+{jw}{L}_{0}+{Z}_{s}$$
(2-7)

Substituting equations (2-5) and (2-6) into equation (2-7), the real part of Zin can be derived as

$${{Re}}({Z}_{\text{in}})={R}_{0}+2\pi f{L}_{0}{k}^{2}{Q}_{s}\frac{f/{f}_{s}}{1+{Q}_{s}^{2}{\left(f/{f}_{s}-{f}_{s}/f\right)}^{2}}$$
(2-8)

Equation (2-6) reveals that Rs is inversely proportional to Qs of the LC sensor, such that any variation in Rs leads to changes in the amplitude of Re(Zin) as indicated by equation (2-8). These changes can be detected by external devices. Besides, if Qs is sufficiently large such that1/(4Q2s)≪1, then fs approximates f = fRe-max with a maximum Re(Zin) according to equation (2-8), which implies that variations in Ls and Cs can be directly observed by monitoring changes in fRe-max.

In addition, Zin can be converted to the reflection coefficient (S11) according to the following expression:

$${\left.{S}_{11}=\frac{{Z}_{{in}}-{Z}_{0}}{{Z}_{{in}}+{Z}_{0}}\right|}_{{Z}_{0}=50\varOmega }$$
(2-9)

where Z0 = 50 Ω represents the characteristic impedance of the feed. In this case, variations in Rs, Ls and Cs can also be detected by observing the S11 curve of the reading coil, which can be obtained with a Vector Network Analyzer (VNA).

Based on the above theory, various sensors have been developed44,45. For instance, Sridhar et al. introduced a hydrogel pH sensor based on LC resonant circuit44. Changes in pH values alter the dimensions of the hydrogel elements, leading to the variation of Ls and resulting in a frequency shift in the, which can be detected by monitoring the frequency shift of S11. Ren et al. describes the design of an LC resonant passive sensor for relative humidity and temperature monitoring45. In this design, environmental humidity affects the capacitance, leading to the change in the resonant frequency, while ambient temperature influences the resistance, thereby altering the quality factor. Consequently, by measuring the Re(Zin) of the reading coil, variations in ambient temperature and relative humidity can be accurately recorded.

Antenna for powering

In addition to LC sensors, magnetic coupling can be utilized in NFC systems consisting of two coils, where energy is transferred from the primary to the secondary coil, realizing power transmission in near field. When excluding the integrated circuit (IC) components, the equivalent circuit of NFC system can be simplified as depicted in Fig. 2e, where the mutual inductance between the two coils can be equivalent to a magnetic coupling transformer with a coupling coefficient K. In this circuit, the primary coil antenna is matched with the voltage source through the capacitor Cs. The resistor Rs1 and Rs2 accounts for the losses in the primary and secondary coil antennas, respectively. Inductor L1 and L2 serve as series resistors. The capacitors CP1 and CP2 represent the parasitic capacitances of the primary and secondary coils, while CR is the tuning capacitor for optimal impedance matching, and RL represents the load.

The design of planar spiral antennas varies depending on application requirements. While planar spiral antennas can adopt diverse geometries (including circular, rectangular, and polygonal configurations), each structure exhibits distinct electromagnetic characteristics, as shown in Fig. 2f, g. Circular coils leverage rotational symmetry to achieve uniform magnetic flux distribution and minimize edge effects, with key parameters such as the radius of curvature and angular alignment directly influencing their quality factor and coupling efficiency. Conventional polygonal coils, such as hexagonal designs, feature seamless tiling and flexible modularity, optimizing performance in irregular layouts and maximizing anti-misalignment characteristics. The number of sides and symmetry of polygonal coils critically affect their performance. In contrast, rectangular or square coils provide a larger effective coupling area compared to circular or elliptical counterparts with equivalent horizontal and vertical dimensions, owing to their orthogonal symmetry and maximized edge utilization. This rectangular coil consists of a metal coil on top and a substrate below, where the outer and inner diameters of the coil are denoted as d0 and di, respectively, w and s are the width of each coil wires and their separation space. Due to its predictable field confinement, fabrication simplicity, and compatibility with standard planar manufacturing processes, it is widely employed in wireless communication, NFC/RFID, and electromagnetic induction systems.

The key factors influencing transmission characteristics include the coupling coefficient K, coil inductance L and quality factor Q46, which are expressed as follows47:

$$L=\frac{1.27\times {\mu }_{0}{n}^{2}{d}_{{avg}}}{2}\left[{In}\left(\frac{2.07}{\phi }\right)+0.18\phi +0.13{\phi }^{2}\right]$$
(2-10)
$$K=\frac{M}{\sqrt{{L}_{1}{L}_{2}}}{\rm{with}}{M}=g\mathop{\sum }\limits_{i=1}^{{n}_{1}}\mathop{\sum }\limits_{j=1}^{{n}_{2}}{M}_{{ij}}\left({r}_{i},{r}_{j},D\right)$$
(2-11)
$$Q\approx \frac{\omega L}{{R}_{s}}\,{\rm{for}}\,{\rm{small}}\,{C}_{{\rm{p}}}\,{\rm{or}}\,{\rm{low}}\,f$$
(2-12)

where davg = (d0 + di)/2 represents the average radius, φ = (d0 - di)/(d0 + di) represents the fill factor, and μ0 = 4π × 10-7 H/m represents the vacuum permeability. The coupling inductance M and the number of coils turns, denoted n1 and n2 for the primary and secondary coils, respectively, also influence the system’s performance. Besides, ri and rj refer to the radius of the ith and jth coil turns of the primary and secondary coils, respectively, and D represents the distance between the two coils. The constant g is specific to the shape of a planar spiral coil (PSC), with g = 1.1 for square-shaped PSCs. The angular frequency ω = 2πf defines the system’s operational frequency.

When both coils are tuned to the operating angular frequency, such that ω = 1/(C1L1)1/2 = 1/(C2L2)1/2, maximum transmission efficiency can be achieved47:

$$\eta =\frac{{K}^{2}{Q}_{1}{Q}_{L}}{1+{K}^{2}{Q}_{1}{Q}_{L}}\cdot \frac{{Q}_{L}}{{Q}_{2}+{Q}_{L}}$$
(2-13)

where Q1 and Q2 represent the quality factors of the primary and secondary coil antennas, respectively, and QL represents the loaded quality factor of the secondary coil at resonance, which can be expressed as:

$${Q}_{L}=\frac{1}{{R}_{s2}/\omega {L}_{2}+\omega {L}_{2}/{R}_{L}}=\frac{1}{{R}_{s2}\cdot \sqrt{{C}_{2}/{L}_{2}}+1/{R}_{L}\cdot \sqrt{{L}_{2}/{C}_{2}}}$$
(2-14)

where C2 can be represented as C2=Cp2||CR.

Based on the discussions above, it can be concluded that sensor performance can be reflected on the frequency shift of the antenna, which is caused by variations in its equivalent inductance, capacitance, or resistance. These variations are achieved by incorporating sensitive elements into the antenna structures, consequently changing the dielectric properties of the substrate, changing the dimensions of the antenna, or introducing inductive and capacitive loadings. To maximize transmission and power transfer efficiency in NFC coils, careful attention must be given to the coil’s dimensions, optimizing inductance, capacitance, and resistance for resonant frequency and impedance matching. Additionally, proper alignment and placement are crucial; the primary and secondary coils must be axially aligned and kept at an optimal distance. Any axial misalignment or distance variation significantly reduces transmission efficiency between the coils.

NFC/RFID-based flexible physical sensors

The NFC/RFID-based sensor systems can be broadly categorized into physical sensors and biological/chemical sensors, depending on their sensing principles and application scenarios. This section provides a comprehensive exploration of strategies and approaches for incorporating NFC/RFID antennas into wearable or implantable physical sensing systems, covering single to multiple physical quantities monitoring both in vitro and in vivo. Specific focus is given to wearable strain sensors, wearable multimodal sensors, and implantable sensors.

Wearable strain sensors

Strain sensing plays a vital role in physiological monitoring, with applications ranging from respiratory tracking to pulse wave monitoring, offering opportunities for continuous and noninvasive health assessment. One notable application is in the detection of intraocular pressure (IOP), a critical parameter in the management of glaucoma, which is the second leading cause of blindness worldwide, following cataracts48. Traditionally, IOP measurement is performed using a Goldman applanation tonometer, a standard medical device that requires the expertise of medical professionals and limits patient monitoring to specific times and locations. Additionally, this method necessitates the use of anesthesia, further complicating the procedures.

Currently, smart contact lenses equipped with NFC/RFID antennas have been reported as IOP sensors. These devices incorporate a NFC/RFID coil within a flexible lens, facilitating wireless, real-time IOP monitoring—thus offering a more practical and convenient alternative to wired smart lenses49. A key innovation in these devices is the hybrid rigid-flexible structural design, which enhances sensitivity by concentrating strain in the flexible component50. Strain sensors in these smart contact lenses are generally categorized as either resistive or capacitive. As IOP increases, the resistance in resistive sensors rises, leading to a linear shift of the S11 value at the resonant frequency (Fig. 3a)51. In contrast, capacitive strain sensors detect corneal dilation caused by increased IOP through changes in the capacitor’s shape, thus enabling wireless IOP monitoring via resonant frequency changes induced by capacitance variations. For instance, Fig. 3b depicts a capacitive contact lens-based sensing system that utilizes a pyramidal microstructure to enhance pressure sensitivity52. This system leverages capacitive sensing and a dielectric elastomer to detect corneal dilation from elevated IOP. An external coil connected to a VNA reads the S11 value to track IOP readings, with readers integrated into the glasses frame for simplified wireless data acquisition.

Fig. 3: A variety of NFC/RFID-based contact lens designs with the ability to monitor IOP.
figure 3

a Schematic illustration of the resistive wireless IOP sensing contact lens, and the equivalent circuit diagram51. Copyright 2020, ACS. b Schematic diagram of the capacitive smart contact lens and the reader integrated in the glasses52. Copyright 2022, ACS. c Schematic illustration of the mechanism by which an overall flexible contact lens measures IOP53. Copyright 2017, Springer Nature. d Schematic illustration of the contact lens integration system with the introduction of NFC chip, the enlarged part is schematic illustration of the printed free-standing 3D interconnects on the metallic pads of an NFC chip2. Copyright 2021, Springer Nature. e Closed-loop smart contact lens integrated with a flexible drug delivery system and a microchip, which are designed for the monitoring and control of IOP54. Copyright 2022, Springer Nature

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Moreover, contemporary smart contact lenses are trending towards multifunctionality. Figure 3c shows a multiplex system capable of simultaneously detecting tear glucose concentration and IOP. In this system, elevated IOP changes corneal curvature, compressing the dielectric to decrease its thickness and increase system capacitance. Concurrently, the biaxial lateral expansion of the helical coil increases inductance, thus affecting the resonant frequency of the system. The glucose sensor, operating as a resistive element, also influences the S11 value, effectively avoiding signal conflicts53. Another innovative system integrates an NFC chip with a temperature sensor and uses EGaIn for connections, allowing for IOP and temperature detection with just a smartphone equipped with NFC capabilities2, thus greatly simplifying sensor data acquisition and processing (Fig. 3d).

For personalized medicine, mere detection is insufficient; targeted treatment tailored to individual conditions is more beneficial. Such demands have catalyzed a novel class of smart contact lenses integrates a dosing component6, allowing for in situ IOP detection and on-demand medication delivery. In another case, Fig. 3e showcases a highly integrated diagnostic and therapeutic contact lens that combines a chip and a drug delivery system for wireless IOP monitoring and management54, which could hopefully improve glaucoma treatment.

Beyond localized strain sensing such as IOP monitoring, strain sensors are also widely employed to detect dynamic body motions, including joint flexion, muscle contraction, and respiration, offering valuable insights into a broad range of physiological activities. However, many of these devices still depend on wired connections for signal transmission55,56,57,58. To address this, wireless strain sensing systems based on NFC/RFID technology have been developed. For instance, the system illustrated in Fig. 4a employs a Ti3C2Tx MXene strain-sensitive resistor, supported by an NFC smartphone for wireless power supply, signal transmission and reception, making it particularly suitable for electronic skin applications aimed at monitoring finger, palm, or sole movements59. In addition to skin-mounted sensors, wireless strain sensors have also been integrated into clothing as electronic textiles for detecting human motion. Figure 4b showcases a strain sensor made from reduced graphene oxide (rGO)-dyed wool fabric. This sensor, produced through embroidery techniques, seamlessly integrates with a textile-based NFC antenna to enable wireless strain sensing of finger bending60.

Fig. 4: Stretchable NFC/RFID-based strain sensor.
figure 4

a The wireless Ti3C2Tx MXene strain sensor59. Copyright 2020, ACS. b A wireless sensing system with embroidered NFC and rGO/wool-knitted strain sensor60. Copyright 2020, ACS. c A near-field multi-body area network integrated into textiles61. Copyright 2021, Springer Nature. d Battery-free sensor networks based on near-field-enabled clothing62. Copyright 2020, Springer Nature. e Photograph of a RFID sensor node for sensing the pulse on a human wrist38. Copyright 2019, Springer Nature. f Photograph of a person wearing multiple strain sensors38. Copyright 2019, Springer Nature. g The total system of RFID tag sensor incorporating a flexible diode63. Copyright 2021, Springer Nature

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Furthermore, advancements in medical monitoring technology have necessitated comprehensive whole-body movement monitoring, beyond localized areas. This requirement calls for a body area sensing network capable of monitoring multiple body parts. NFC/RFID technology offers a solution by enabling the creation of an extensive network of strain sensors. Such a network is typically composed of multiple NFC sensor nodes that communicate through several partially overlapping flexible planar magnetic resonators (flexible planar coils) (Fig. 4c)61. These sensor nodes can be integrated into clothing, with an external reader providing both power and data transmission. As shown in Fig. 4d, the sensor nodes attach directly to the skin, while the wiring is embedded in the clothing fabric. When the reader approaches one coil, it activates all sensor nodes and receives their signals62, thus simplifying the overall configuration and reducing wiring complexity.

Simplification of sensor node design is also a critical aspect of improving these systems. Bao et al. have developed sensor nodes that consist only of an antenna and a resistive strain sensor, promoting system miniaturization and flexibility38 (Fig. 4e, f). An RFID-based external reader can detect changes in the S11 value of the tag in response to strain, facilitating comprehensive monitoring of human physiological activities. Figure 4g shows another design which features a high-frequency tension diode for rectification and includes an electrochromic display (ECD) pixel63. When the current in the ECD pixel exceeds a specific threshold, a distinctive blue color appears, visually indicating strain on the human body. This visual cue simplifies the interpretation of strain data, providing a straightforward method for assessing physiological conditions.

Wearable multimodal sensors

In the realm of personalized medicine and the rapidly advancing field of wearable biomedical sensors, the detection of isolated physical quantities often proves inadequate for comprehensive patient care. There is a pressing need for wearable medical sensors capable of simultaneously monitoring multiple physiological parameters, thus enabling a more detailed analysis of patient health64. For instance, temperature is a crucial indicator of inflammation, infection, and wound healing potential65, while skin strain is an effective metric for evaluating wound closure and tissue expansion during the healing process66. Consequently, a sensor system that simultaneously tracks temperature and strain would significantly enhance wound care and management (Fig. 5a)37. The smart bandage features a highly sensitive strain sensor that utilizes a Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) microfluidic channel embedded in a PDMS substrate. The resistance of the strain sensor increases as the microchannel expands in response to applied strain. Additionally, the temperature sensor utilizes the thermosensitivity of PEDOT:PSS, where an increase in temperature enhances carrier mobility, leading to a decrease in resistance.

Fig. 5: Flexible wearable NFC/RFID-based sensors that can monitor multiple physical quantities.
figure 5

a The NFC-based smart bandage for wireless strain and temperature real-time monitoring37. Copyright 2021, IEEE. b A photograph of the flexible sensor that monitors the temperature and pressure at the bony prominence before encapsulation15. Copyright 2021, Springer Nature. c Photograph of the battery-free, wireless sensing platform that includes crack-activated pressure sensor, temperature sensor, and GSR sensor. Inset shows the GSR sensor located at the back side of flexible PCB67. Copyright 2023, Springer Nature. d Schematic illustration of the overall system integrated with a wheelchair67. Copyright 2023, Springer Nature. e Sensor arrays that can continuous monitoring and mapping of pressure and temperature distribution68. Copyright 2023, Wiley-VCH. f A group of thin and comfortable wireless temperature and pressure sensor systems distributed throughout the body, the enlarged part is the individual sensor section structure70. Copyright 2018, AAAS. g Illustration of wireless, battery-free multimodal sensors on a residual limb and NFC/BLE modules on the outer surface of a prosthetic socket71. Copyright 2020, AAAS

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In addition to wound management, multimodal sensors are also effectively monitoring pressure injuries. For hemiplegic patients, areas around bone protrusions can rapidly heat up under constant pressure, which can lead to severe pain, functional impairment, skin breakage, and other complications. A specialized device designed to fit the contours of bone prominences includes an NFC System-on-Chip(SoC) and a coil antenna connected to pressure and temperature sensors via serpentine wires (Fig. 5b)15. PDMS encapsulation ensures environmental isolation, electronic protection, and fluid buffering, enhancing the durability and reliability of the sensor. Extending this concept further, Fig. 5c demonstrates a Galvanic Skin Response (GSR) sensor, which builds upon the previous design of Fig. 5b and is capable of measuring pressure, temperature and hydration levels at joint sites to accurately assess pressure damage. Such sensors can be strategically distributed across various body parts forming a comprehensive full-body sensing network. The network, controlled by a multiplexer and an NFC reader, communicates with primary antennas located on the wheelchair (Fig. 5d)67. This setup wirelessly powers all sensors attached to the patient and rapidly reads data from different locations using an NFC-based sequential read protocol, thus providing real-time pressure, temperature, and hydration measurements for each sensor node. The deployment of wireless sensor arrays in areas vulnerable to pressure damage allows for continuous multi-point mapping of pressure and temperature distributions (Fig. 5e)68, offering a more comprehensive understanding and prevention of pressure injuries compared to single-point detection methods69.

In contrast to the aforementioned systems, the configuration shown in Fig. 5f exhibits a higher degree of miniaturization and integration, enabling broad coverage and comprehensive data collection for both temperature and pressure. Furthermore, this data can be converted into thermograms and pressure maps70, offering a visual representation of the wearer’s physiological conditions. Additionally, the multimodal sensing of temperature and pressure can be extended to prosthetics to monitor pressure injuries at amputation sites (Fig. 5g)71.

Implantable sensors

Implantable sensors are essential for capturing critical signals that are not accessible through wearable devices, such as intracranial parameters72 and arterial blood flow. For instance, NFC-based implantable sensors have been designed for real-time monitoring of brain oxygen saturation in mice (Fig. 6a) allows for awake-state measurements due to its compact size and biocompatible encapsulation73,74. Unlike stent-based wireless blood flow sensors75,76 and wireless pacemakers77, these implantable sensors allows for continuous monitoring of vascular pressure, flow rate, and temperature within blood vessels through only a minimally invasive sensing module (Fig. 6b, c)3.

Fig. 6: Different designs of NFC/RFID-based implantable sensors.
figure 6

a Wireless, battery-free optoelectronic systems as subdermal implants for local tissue oximetry (upper)73 and a wireless optoelectronic probe to monitor oxygenation in deep brain tissue (lower)74. Copyright 2019, AAAS; Copyright 2024, Springer Nature. b Subcutaneous implants for wireless power and data transmission3. Copyright 2023, Springer Nature. c Schematic illustration of the sensing part3. Copyright 2023, Springer Nature. d Photograph of the dissolved device placed in a simulated environment (equivalent to 14 days after the device was implanted in a mouse)78. Copyright 2016, Springer Nature. e Biodegradable, flexible and passive arterial-pulse sensor design8. Copyright 2019, Springer Nature. f Wireless, fully implantable cardiac stimulation and recording device for closed-loop pacing and defibrillation79. Copyright 2022, AAAS. g Schematic illustration of the Flexible implantable closed-loop multimodal sensing system80. Copyright 2023, Springer Nature

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Despite the reduced invasiveness, there remain concerns regarding potential tissue damage during and after implantation. Moreover, the use of non-biodegradable materials and electronic components complicates post-implantation management, often necessitating additional surgeries for removal. Addressing these issues, a fully implantable NFC sensor designed for monitoring brain temperature and pressure in mice incorporates bioabsorbable elements, such as magnesium coils, electrodes, interconnections, and silicon resistors, which dissolve within 14 days post-implantation (Fig. 6d)78, Although the NFC chip itself remains non-biodegradable, this design significantly reduces long-term biocompatibility concerns.

For complete bio-absorbability, sensors devoid of electronic chips present a promising solution. As depicted in Fig. 6e, chip-free implantable RFID biosensors facilitate wireless passive monitoring of arterial blood flow, which is crucial for postoperative recovery8. These sensors detect changes in vessel diameter caused by arterial pulsation by monitoring variations in the resonant frequency of the sensor’s LCR circuit. Such changes can be wirelessly detected by an external coil near the implantation site, thus providing continuous blood flow data without the need for invasive retrieval procedures. The use of bioabsorbable materials and a chip-free design eliminates the need for secondary surgeries, thereby enhancing patient safety and comfort.

Diagnostic and therapeutic integrated implantable sensors further extend their utility far beyond conventional detection by incorporating advanced treatment capabilities. Two notable examples illustrate this progress. Figure 6f shows a sensing system designed for cardiac defibrillation research79, which not only monitors ECG signals but also features optical pacing functionality. This dual capability enables precise regulation of cardiac activity, facilitating more effective therapeutic interventions. Moreover, researchers reported an implantable system that integrates both diagnostic and therapeutic functionalities (Fig. 6g), capable of simultaneously multiplex diagnostic (EEG, EMG, and body temperature recording) as well as combined therapeutic (neural modulation through optogenetic electrodes and drug delivery)80. The system operates autonomously in a closed-loop manner, powered by integrated artificial intelligence. The advancement of implantable sensors that combine diagnostic and therapeutic capabilities represents a significant leap forward in medical technology, promising to transform patient care through more precise and responsive interventions.

NFC/RFID-based flexible bio/chemical sensors

Biomarkers in exhaled gas and biofluid are crucial for early disease diagnosis and health monitoring. The process of detecting these biomarkers typically involves chemical reactions, necessitating more complex electronic systems for signal transmission compared to physical sensors. Integrating NFC/RFID technology with flexible biological and chemical sensors addresses these challenges by enabling miniaturization and facilitating more convenient data acquisition compared to traditional sensing systems. This section reviews the advancements in flexible gas sensors for environmental monitoring, food safety, and breath analysis as well as biological fluid sensing systems for detecting biomarkers in sweat, interstitial fluid, and tears.

Gas sensors

Gas sensing using NFC/RFID technologies for wearable/implantable biomedical applications remains an emerging field5,81, while significant advancements in environmental81,82 and food safety monitoring83,84 have demonstrated the feasibility and versatility of NFC/RFID-based gas sensors. These applications are closely related to human health—exposure to harmful gases in the environment or consumption of spoiled food can pose serious risks—and are particularly relevant for healthcare personnel, industrial workers, and consumers who require real-time access to safety information. Therefore, existing systems in these domains offer valuable design insights for future development of wearable and implantable biomedical gas sensors.

In environmental gas monitoring, detecting toxic gases such as ammonia is critical not only for public safety but also for occupational health. Traditional ammonia sensors often require high operating temperatures81,82, while recent advancements have led to the development of highly sensitive ammonia sensors capable of functioning at room temperature85,86,87. Although these sensors can be integrated into wearable smart bracelets, they still depend on external power supplies and contain rigid components that limit their miniaturization and flexibility. To address these limitations, flexible NFC antennas offer a promising solution. For example, the ammonia sensor using a wireless and passive NFC tag shown in Fig. 7a integrates a resistive sensor that is sensitive to ammonia88. This sensor can be read using a smartphone, displaying an “on” state when the concentration is below the threshold. As the surrounding ammonia gas concentration exceeds the threshold, the circuit resistance rises (within 1 min of exposure to 35 ppm NH3, ΔRs = 5.3 ± 0.7 kΩ), causing the chip to switch from active state to inactive state, resulting in an “off” state, thereby enabling wireless semi-quantitative detection of ammonia. Furthermore, this approach has been extended to detect other gases by assembling an array of NFC tags with different threshold resistances89, allowing for binary-coded detection of ethanol gas concentrations from 1 ppm to 5 ppm.

Fig. 7: NFC/RFID-based sensors for gas monitoring.
figure 7

a Construction of NFC tags for semi-quantitative detection of ammonia and explosive gases88. Copyright 2014, NAS. b NFC tag used to detect gases produced by meat spoilage84. Copyright 2018, ACS. c GUI interface on a smartphone displaying detecting results of various gases and humidity in food packaging90. Copyright 2017, ACS. d Smart facemask with integrated flexible NFC tag for wireless CO2 monitoring5. Copyright 2022, Springer Nature. e Structure of a RF-based sensor for respiratory virus detection in forms of aerosol and saliva droplets94. Copyright 2024, Springer Nature. f Mechanism of transduction of electrical signal94. Copyright 2024, Springer Nature

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Food safety, with direct implications for human health, is another critical area where gas sensors are employed to detect spoilage-related gases. Oxygen is a key factor in food spoilage and can be detected by NFC tag sensors embedded within food packaging83. Additionally, biogenic amines and ammonia released during the spoilage of food, particularly meats, are also key indicators that can be monitored using NFC tag sensors (Fig. 7b)84. In another design, tag sensors integrate four distinct sensing membranes, enabling the detection of multiple gas concentrations as well as temperature and humidity levels within the packaging. Each membrane elicits an optical response (luminescence or colorimetric change) to the target gas, with the results captured by a color detector. The test results of target gas concentrations are then intuitively transmitted to a smartphone for real-time acquisition via the NFC antenna90 (Fig. 7c).

In clinical settings, monitoring exhaled gases is crucial for early disease diagnosis. For instance, elevated ammonia levels in breath are indicative of kidney disease91,92. Moreover, rebreathing of carbon dioxide trapped in masks can negatively impact the human body. While current wearable sensors can detect ammonia in exhaled air85,93, they often require external power modules, limiting their practicality. To overcome this, NFC modules have been applied to wearable smart gas sensing devices. Figure 7d shows a smart mask featuring a flexible NFC tag integrated with a photochemical sensor, which non-invasively measures the carbon dioxide concentration inside the mask5. The sensor and electronic components are mounted on a flexible substrate and are powered and communicate wirelessly via NFC technology, thereby enhancing the mask’s flexibility and integration capabilities.

In addition to gaseous molecules, aerosols—airborne particles that may carry pathogens—are also of significant biomedical relevance. The detection of aerosols shares similar device design principles with gas sensing, particularly in terms of transduction mechanisms and integration strategies. This similarity enables the adaptation of NFC-based gas sensor platforms for real-time, non-invasive monitoring of aerosol-borne biomarkers, such as respiratory viruses. Figure 7e shows a wireless RF-based immunoassay system uses an immuno-responsive hydrogel-modulated resonant (ImmHR) sensor for rapid virus detection (e.g., SARS-CoV-2, H1N1, RSV)94. The hydrogel, grafted with viral antigens and antibody-conjugated gold nanoparticles, swells upon antigen binding, altering the dielectric constant between paired RF resonators (Fig. 7f). This shifts the resonant frequency, enabling high sensitivity (limit of detection down to fg/L) and fast detection (<10 min) while minimizing environmental interference. Such integration of NFC-based sensors into smart devices opens new possibilities for real-time, non-invasive health monitoring and pathogen detection.

Sensors for metabolites monitoring in biofluid

Biological fluids, such as sweat, urine, tears, and blood, are rich in biomarkers like metabolites, electrolytes, proteins, and heavy metals making them invaluable for rapid disease screening and health management. Current NFC sensors often focus on monitoring fluid volume using commercial humidity sensors (Fig. 8a)95 or capacitive sensing methods96. However, these sensors primarily assess the wearer’s condition based on body fluid volume and lack quantitative biomarker analysis. Therefore, there is a demand for sensors that can quantitatively detect specific biomarkers in biological fluids to enhance disease detection and prevention. Recent advancements have shown promise in this area. The modified electrode arrays have been used to quantitatively detect biomarkers in sweat by means of electrochemical sensing16,97,98. Despite these advances, some sweat sensors99,100 still rely on batteries to power the device, which limits their miniaturization and flexibility. To address the limitation, a wireless passive electrochemical sensing patch based on NFC technology has been developed, including different electrochemically modified electrode arrays on the surface (Fig. 8b)101. The thin and flexible NFC antenna provides energy for the sensor patch wirelessly. Antenna and electronic components are integrated onto a flexible circuit board, improving system integration and reducing device size101. The electrode array can be modified with ionic sensitive films to detect the concentrations of various ions (Na+, K+, H+, Ca2+, Cl-) and glucose in sweat101,102,103. Furthermore, the introduction of microfluidic channels, as demonstrated by Bandodkar et al., enables efficient sweat distribution across multiple electrodes, facilitating multimodal sensing. (Fig. 8c)104. The sweat is collected and transported to individual chambers by a microfluidic substrate that houses electrochemical sensing electrodes and a variety of colorimetric assays that simultaneously detect lactic acid, glucose, chloride, pH, and sweat rate.

Fig. 8: NFC/RFID-based sensors used to monitor biomarker concentrations in biological fluids.
figure 8

a Smart textile NFC sensor that can be integrated on clothing for surface temperature and humidity sensing95. Copyright 2020, IEEE. b Side-view of the sweat monitoring patch, including an NFC-enabled flexible circuit board and a stretchable electrode array101. Copyright 2019, Elsevier. c A battery-free hybrid system which NFC electronics can be reversibly magnetically attached to a microfluidic patch104. Copyright 2019, AAAS. d A RFID sensing device implanted subcutaneously to monitor the concentration of glucose in tissue fluid109. Copyright 2015, IEEE. e Electronic systems and charging coils of wearable microneedle array111. Copyright 2022, Springer Nature. f A smart contact lens which can simultaneously monitor intraocular pressure and glucose53. Copyright 2017, Springer Nature. g A smart contact lens with double electrode structure115. Copyright 2012, IOP. h Wireless smart contact lens for diabetic diagnosis and therapy116. Copyright 2023, AAAS

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Based on the strong correlation between the glucose concentrations in interstitial fluid and tears with blood glucose levels105,106,107,108, many wireless glucose sensors are reported. Approaches for monitoring tissue fluid glucose can be categorized into subcutaneous implantation, reverse iontophoresis, and microneedle sampling. Subcutaneous implants allow continuous monitoring of biomarkers in tissue fluid. An RFID-based subcutaneous implant device can continuously monitor blood glucose concentration in tissue fluid (Fig. 8d)109, but it remains invasive and poses risks such as infection and biocompatibility issues. In contrast, reverse iontophoresis allows non-invasive extraction of interstitial fluid using a mild current between two electrodes on the skin surface110. Another solution is to collect interstitial fluid through wearable microneedles. Tehrani et al. have reported a wireless wearable microneedle sensor array (microneedle diameter: ~200 μm) for monitoring multiple biomarkers (alcohol, glucose, and lactate) in interstitial fluid, and charges its battery via a near-field coil (Fig. 8e)111.

The glucose concentration in tears is also closely related to the blood sugar level112. Unlike traditional wired transmission methods, which can obstruct vision and increase infection risks, smart contact lenses with RFID coils and chemically modified electrodes provide a practical solution for wireless tear sensing (Fig. 8f)53. The highly sensitive detection of glucose is generally achieved through glucose oxidase modified electrode113,114. To further enhance the selectivity, there are contact lenses can compensate for interfering electroactive substances in tears by using a dual-sensor structure (one activates glucose oxidase, and the other deactivates it)115, thereby improving the sensor’s accuracy (Fig. 8g). Additionally, smart contact lenses can also integrate chips and flexible drug delivery systems that can be wirelessly controlled (Fig. 8h), enabling real-time biosensing of ocular biomarkers and on-demand drug treatment for eye treatments116.

NFC/RFID-based drug delivery systems

Integrating NFC/RFID antennas into drug delivery systems (DDS) is an emerging direction in personalized medicine, enabling real-time drug delivery, diagnosis-therapy closed-loop systems, enhanced flexibility and miniaturization for wearables and implants. Radio frequency waves from external coils serve two main functions in DDS: enabling communication and powering the DDS117,118, and directly stimulating the DDS for drug release28. The former application is typically employed in wearable NFC drug delivery patches, while the latter is more commonly applied in implantable RFID drug delivery devices.

In wound healing applications, NFC technology enables the creation of smart wound dressings that can monitor wounds and deliver drugs without adding bulk. For instance, a wireless passive NFC-based smart wound dressing has been developed to track temperature, pH, and uric acid levels on the wound surface119 (Fig. 9a). This represents a significant advancement over earlier smart dressings that monitored only a single parameter, such as temperature120 or pH121, allowing for a more accurate assessment of the infection status. Data collected from the dressing is transmitted to a smartphone, which evaluates drug delivery needs, and the smart dressing releases the drug via an electric signal-controlled module. Another example is a wireless closed-loop smart dressing that releases drugs based on feedback from wound temperature and humidity, using heated liquid metal coils to trigger the release of drugs encapsulated in thermosensitive hydrogels (Fig. 9b)12. Beyond wound care, wearable NFC patches have been used in the treatment of neurological diseases by electrically triggering drug release via microneedles122.

Fig. 9: NFC/RFID-based wearable and implantable drug delivery systems.
figure 9

a A smart wound dressing that detects the various physiological parameters of the wound surface and delivers drugs119. Copyright 2021, Wiley-VCH. b A wireless and closed-loop smart dressing that releases drugs by heating liquid metal coils12. Copyright 2023, Wiley-VCH. c Schematic illustration of a soft, wireless implantable drug delivery system in the subcutaneous region with images of the front and backside of the system11. Copyright 2021, AAAS. d The biodegradable RF drug delivery device can realize multiple drug delivery129. Copyright 2020, AAAS. e Drug release simulation129. Copyright 2020, AAAS. f The degradation process of a soft implantable energy supply system that can be charged wirelessly130. Copyright 2023, AAAS

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Epidermal NFC drug delivery patches are primarily used for monitoring and treating surface wounds due to the skin barrier, which often results in slow drug release rates and limited drug options123. However, many diseases necessitate targeted intracorporeal drug delivery, where implantable NFC/RFID-based systems can offer rapid and precise therapy124,125,126,127. For instance, implantable devices with flexible radio frequency antennas can harvest energy through inductive coupling from an external coil, which can be used to heat and drive drug release for treatments like brain tumor therapy126. Another strategy is to convert the radio frequency signals received by the RFID antenna into direct current voltage, which can chemically degrade the metal layer encapsulating the drug128,129. or generate gas through water electrolysis to trigger the drug release (Fig. 9c)11. Noted that, the use of coils with different resonant frequencies is controllable which can allow for multiple, sequential drug releases (Fig. 9d, e)129.

Biocompatibility is crucial for implantable radio frequency drug delivery devices. Researchers have proposed a biodegradable wireless power supply system with excellent biocompatibility, delivering direct current voltage for in-body wireless drug delivery. Apart from the rectifier module, the coils, wires, and capacitors are made from biodegradable materials. When placed in a phosphate-buffered saline (PBS) solution (pH 7.4, 80 °C), the Mg interconnect wire and receiver coil fully dissolved after 15 days, followed by the degradation of the Zn negative electrode and MoS2/rGO positive electrode of the capacitor into negligible black spots over the next 40 days (Fig. 9f)130.This illustrates the potential of biodegradable materials for implantable bioelectronic applications.

Conclusion and perspective

The integration of NFC/RFID technology into flexible sensing systems has overcome the limitations of wired connections and bulky power supplies, driving the development of personalized, multifunctional wearables and implants. NFC/RFID-based sensors facilitate real-time, noninvasive monitoring of diverse health related physiological indicators, enable real-time, noninvasive monitoring of various physiological indicators, including intraocular pressure, strain, electrophysiological, and biochemical parameters, enhancing personalized health management with their convenience and versatility. Implantable applications further broaden their utility by capturing physiological signals within the human body. Integrating drug delivery function with sensors further empower closed-loop diagnosis and therapy capabilities to the NFC/RFID-based wearables and implants.

Despite significant progress in developing NFC/RFID-based functional systems, several challenges remain. For antenna systems, data or power transmission efficiency is highly dependent on factors such as antenna shape, conductivity, alignment, and distance changes. In flexible sensors, ensuring mechanical compliance presents significant challenges to maintain system stability. Driven by the pursuit of higher integration and miniaturization, NFC/RFID-based bio/chemical sensors are facing increasing challenges, including accurate detection of multiple biomarkers, transition from qualitative to high-precision quantitative sensing, and management of the complexity associated with monitoring diverse physiological parameters. In implants applications, extra challenges brought by the implantable devices in vivo, such as the signal attenuation and distortion within the body still need to be addressed (Fig. 10). Moreover, power transmission and data exchange can generate heat, which is a concern for implantable sensors as it can damage surrounding tissues or cause discomfort.

Fig. 10
figure 10

Developing from wearable devices on the body surface to implantable devices in vivo, future NFC/RFID-based systems aim to cover both routine monitoring to clinical diagnostics, and enable real-time monitoring and control of intervention strategies via mobile terminals, offering promising solutions for next-generation smart healthcare and personalized medicine

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Beyond technical barriers, the commercialization of NFC/RFID-based biomedical devices must also contend with multifaceted challenges related to safety and regulatory compliance. Electromagnetic compatibility is a critical concern, as NFC/RFID signals may interfere with sensitive medical equipment like pacemakers and infusion pumps, necessitating rigorous EMI testing and conformance to compatibility standards. The wireless nature of these systems also introduces data privacy and cybersecurity risks; without strong encryption and authentication, patient information may be vulnerable to unauthorized access. Regulatory frameworks for such devices vary globally—for instance, the U.S. FDA classifies certain RFID-enabled medical devices as Class II, subject to strict safety and performance evaluations. Similar requirements exist in the EU, China, and other regions, with differences in frequency bands, power constraints, and certification processes. Therefore, successful clinical translation requires not only technological innovation, but also proactive regulatory navigation and robust implementation of safety and data protection strategies.

These challenges together form a roadmap for future research (Fig. 10). The development of new functional materials (highly stretchable, conductive, while ideally, be bioabsorbable) and innovations in antenna design will not only address current limitations but also set the stage for future advancements. In addition, commercialization and clinical application of these sensors involves further reducing manufacturing costs through the maturation of flexible electronics manufacturing technologies, thus facilitating the transition from concept to practical wearable devices. As flexible sensors become more integrated with mobile health applications, cloud computing, and artificial intelligence, they will be able to offer more personalized health management solutions. We believe that as technology continues to evolve and market demand increases, flexible NFC/RFID-based wearable and implantable systems will make significant contributions to medical care by improving health management and patient outcomes.