Fig. 3: Benchtop characterization of the biointerface.

a–c Strain sensing module: comparison of strain–load curves measured using standard wired system and wireless OSE device (a); strain profile measured with the wireless device under progressively increasing load (b); and strain profiles measured with wired system and wireless device under cyclic load (c). Benchtop test setup where the strain gauges are attached on a piece of sheep bone and the load is applied with a MTS system. d–f LED module: photographs of devices inserted at the bone–tissue interface, with µ-ILED on the bottom (left), on the top (middle), and on both sides (right) (d); current profile of the µ-ILED operating at frequencies of 5, 10, and 20 Hz with pulse width of 20 ms (e); current and optical power as functions of driving voltage of the µ-ILED used (f). Scale bar in (d), 5 mm. g–i Thermal sensing module: wirelessly logged ADC values as a function of temperature (g); wirelessly measured change in temperature using the NTC thermistor with the micro-heater driven at various levels of power, demonstrating a sensing resolution of <10 mK (h); thermal impact of an µ-ILED operating at various optical powers and duty cycles in PBS solution measured wirelessly with a co-located NTC thermistor (i). Insets of (h) and (i), schematics showing the layout of thermistor-micro-heater (h) and thermistor-LED front-end (i).