BME Frontiers / 2021 / Article / Fig 1

Research Article

Bioresorbable Multilayer Photonic Cavities as Temporary Implants for Tether-Free Measurements of Regional Tissue Temperatures

Figure 1

Bioresorbable multilayer photonic cavity structure for remote, wireless monitoring of temperature: (a) Left: cross-sectional SEM image of the multilayer structure. Right: schematic illustration of the compositional layout. The sensor consists of a cavity defined by a distributed Bragg reflector (DBR) (labeled SiOx/SiNy), a separate Fabry-Perot (F-P) cavity (labeled Si layer), and a polymeric substrate (labeled PLGA); (b) schematic illustration of a device based on this structure implanted into deep tissue. Tracking the positions of peaks in the measured reflection spectra enables measurements of changes in the temperature of local tissues; (c) image of a flexible device supported on a bioresorbable film of poly(lactic-co-glycolic acid) (PLGA); (d) reflection spectra measured in free space as a function of ambient temperature; (e) experimental and simulation results for the reflection spectrum of a multilayer photonic cavity; (f) experimental and simulation results of shifts in the positions of peaks in these spectra as a function of temperature; (g) temperatures determined from these spectra compared with those captured using a commercial thermometer (Neurolog, Inc.); (h) images of a device collected at several stages of dissolution in a solution of phosphate-buffered saline (PBS, ) at room temperature. The periodic arrays of holes created during device fabrication for reliable transfer printing show a gradual increase in size during immersion in PBS.