Bioresorbable Multilayer Photonic Cavities as Temporary Implants for Tether-Free Measurements of Regional Tissue Temperatures
In vitro demonstrations of temperature sensing: (a) reflection spectra of a multilayer photonic cavity measured in free space and through pieces of raw chicken breast with thicknesses of 1 cm, 2 cm, 3 cm, and 5 cm; (b) reflection spectra of a device under a 1 cm thick piece of chicken tissue at various temperatures; (c) reflection spectra of a device under a 5 cm thick piece of chicken tissue at various temperatures; (d) a denoising algorithm determines the location of peaks for each measured spectrum. A flow chart that illustrates the algorithm appears in Supplementary Figure 3; (e) reflection spectra of a bare 10 μm thick PLGA film, as coated with a 50 nm thick film of Mg, and a 50 nm thick film of W, respectively. The spectra show a significant increase of reflectivity by coating a bioresorbable metallic layer (W or Mg); (f) mechanical response of a bioresorbable multilayer photonic cavity structure to bending, as determined by finite element analysis. The results show the strain distribution of a device (,) during bending to a radius of curvature of 1.5 mm. Supplementary Figure 7 shows the corresponding strains and stresses for each layer; (g) a zoom-in view of the strain distribution at a cross-sectional area (corresponding to the dashed square in (f)) of the multilayer photonic cavity structure. The fracture strain for both SiOx and SiNy is around 1%.