Fig. 2: Design and characterization of iMASSAGE technology.

a Representative TEM image of photothermal converter cuttlefish ink nanoparticles (CINPs) for wireless signal conversion. Scale bar, 100 nm. b The absorption spectra of CINPs and the emission spectra of white μLED. Adequate spectral overlap brought about subsequent photothermal conversion. c Transmittance of the hydrogels with different ratios of NIPAAm (95%, 94%, and 93%) over temperature. The LCST of hydrogels was determined by the temperature at 50% transmittance. d Volumetric change of hydrogel-encapsulated iMASSAGE device under wireless-powered stimulation (1 W, with or without CINPs, n = 3 independent experiments). e Representative SEM images of the internal aperture of iMASSAGE device in its original state (0 min), the wireless-induced contraction state (2 min) and relaxation state (8 min) observed by SEM. Scale bar: 50 μm. f Storage modulus of iMASSAGE device over time (1 W, n = 3 independent experiments). g Young’s modulus by calculating the slope of stress-strain curve of device at 10% strain (n = 3 independent experiments). h Strain distributions of embedded cell on contractable hydrogel at different time points under stimulation (Top view). i The Young’s modulus changes of iMASSAGE system as a function of wireless on-off stimulation. All data are presented as mean ± s.d. Source data are provided as a Source Data file.