Fig. 1: Design, fabrication, and working principle of the soft photoacoustic patch.
From: A photoacoustic patch for three-dimensional imaging of hemoglobin and core temperature
a Schematics of the device structure and the working principle. The patch comprises an array of VCSELs and an array of piezoelectric transducers, interconnected by serpentine copper electrodes. All components are encapsulated in Ecoflex. Upon absorption of the optical energy, the hemoglobin molecules in red blood cells undergo thermoelastic expansion and radiate acoustic waves into the surrounding media. The photoacoustic waves will be collected by the transducer array and then relayed to a backend system for data processing. AlN: aluminum nitride. VIA: vertical interconnect access. VCSEL: vertical-cavity surface-emitting laser. b Optical photographs of the soft photoacoustic patch under different modes of deformation, including bending on a developable surface, wrapping on a nondevelopable surface, and stretching and twisting. Insets in the middle and right panels are optical micrographs of a single transducer element and a VCSEL diode, respectively. c Infrared camera images of the soft photoacoustic patch when the VCSELs (850 nm laser wavelength) are in operation under different modes of deformation, including stretching, bending, and twisting.
