Fig. 4: The design of the bottom layer, and the characterization as well as safety test of Bio-PS.
a Schematic illustration of the cross-section of the bottom layer. b Thermoelectric figure of merit (Z1/R(t), thermoelectric figure of merit defined by resistance instead of electrical conductivity and Seebeck coefficient (S(t)) of TE generator at different qualitative temperatures. c Thermal conductivity of the phase change material (PCM) and black carbon-modified PCM (M-PCM) at varied temperatures. d The temperature distribution through the center of the bottom layer under constant heat flow for 10 min predicted by Ansys, and the statistical curve of temperature with different lengths of PCMs (L) The heat flux was 2.0 W. e Time-dependent open circuit voltage output by TE generator with the bottom layer of PCM (red line), the modified PCM (blue line), and the combination of modified PCM with cooling fin (black line). The slight decrease in the open circuit voltage resulted from the fluctuation of temperature during the phase transition of PCMs. f The determination of temperature change relative to body temperature (37 °C) on the upper and lower surfaces of the packaged Bio-PS, under NIR-II light irradiation with LPD of 0.30 W cm−2 for 10 min. g The changes of open circuit voltage of Bio-PS over the cycles of on–off NIR-II light irradiation with the different LPDs. h, The comparison of maximum output power between the PTE converters with or without the use of the bottom layer under NIR-II light irradiation with different LPDs.
