Two-Photon Polymerization in Advanced Microfabrication

Two-photon polymerization is a nonlinear laser‐based additive manufacturing technique that employs tightly focused femtosecond pulses to initiate polymer crosslinking through simultaneous absorption of two photons. By confining photochemical reactions to a femtolitre‐scale focal volume, it achieves true three‐dimensional structuring with sub‐100-nanometre feature sizes, surpassing the diffraction limit of conventional lithography. This capability has enabled the fabrication of freeform micro-optical elements, metamaterials, microfluidic components and biomedical scaffolds with exceptional precision and design freedom. Key advantages include isotropic resolution, minimal heat‐affected zones and compatibility with a wide range of photosensitive materials. Ongoing efforts address throughput limitations, material diversity and multi‐material integration, paving the way for scalable 4D microprinting, smart actuators and large‐area nanomanufacturing. The technique’s global significance spans telecommunications, soft robotics, lab-on-a-chip platforms and next-generation photonic systems.

Research from Nature Portfolio

Innovations in parallelization of the writing process using digital micromirror devices have demonstrated the simultaneous generation and individual control of multiple focal spots at kilohertz rates, enabling rapid fabrication of complex truss and woodpile architectures with ∼500-nanometre resolution. Advances in stimuli-responsive polymer networks have been achieved by modulating local exposure dose to create hetero-microstructures that undergo programmable shape changes in response to temperature and light. These developments offer new routes to reconfigurable micromachines, soft actuators and adaptive photonic devices with finely tuned mechanical and optical properties.

Research from all publishers

Recent comprehensive reviews have highlighted the transition from static to active printable materials in multi-photon 3D laser printing, introducing liquid crystalline elastomers, hydrogels and shape-memory polymers for applications in microrobotics, photonics, microfluidics and life sciences. High-precision multi-focus femtosecond laser sculpting of glass has been developed to produce complex three-dimensional microstructured glass with submicrometre accuracy, exploiting beam-shaping techniques for scalable processing. In parallel, a two-photon curable silica nanocomposite resin has been formulated and thermally converted to transparent fused silica glass, generating true three-dimensional microoptical and biomedical components with tens of micrometre resolution and nanometre-scale surface smoothness.

Two-Photon Polymerization in Advanced Microfabrication publication trend

The graph below shows the total number of articles in two-photon polymerization in advanced microfabrication across all publications each year (not limited to Nature Index journals).

Technical terms

Two-photon polymerization: A nonlinear photochemical process in which a photoinitiator absorbs two photons simultaneously to initiate polymer crosslinking within a tightly focused laser spot, enabling three-dimensional structuring beyond the diffraction limit.

Direct laser writing: A laser-based additive manufacturing technique that uses a focused beam to induce local polymerisation or material modification in a photosensitive medium, facilitating mask-free three-dimensional microfabrication.

Photoresist: A light-sensitive chemical formulation that undergoes a change in solubility upon photon exposure, serving as the basis for two-photon polymerization and other lithographic processes.

Voxel: A three-dimensional volume element fabricated in two-photon polymerization, representing the smallest unit of resolvable structure within a printed object.

Digital micromirror device (DMD): An array of microscopic mirrors that can be individually switched to modulate light patterns for parallelised exposure, increasing throughput in multi-focus two-photon polymerization.

References

1. Three‐dimensional optical laser lithography beyond the diffraction limit. Laser & Photonics Review (2012).
2. Ultrafast multi-focus 3-D nano-fabrication based on two-photon polymerization. Nature Communications (2019).
3. Controlling the shape of 3D microstructures by temperature and light. Nature Communications (2019).
4. Recent Advances in Multi‐Photon 3D Laser Printing: Active Materials and Applications. Advanced Materials (2023).
5. High-precision multi-focus laser sculpting of microstructured glass. Opto-Electronic Advances (2024).
6. Two‐Photon Polymerization of Nanocomposites for the Fabrication of Transparent Fused Silica Glass Microstructures. Advanced Materials (2021).