Design of injectable and biodegradable metagel ultrasonic sensor. a, Metagels as wireless intracranial physiology sensors using ultrasound reflection. b, Metagel samples and puncture needle for delivery. c, Metagel structure. d, Metagel degrading following 1?month in PBS solution at 37?°C; dashed line delineates the shape of the metagel. e, Working principle of metagels based on environment-induced microdeformation. f, Peak frequency shifts of metagel due to deformation. g, Energy band structures of metagel. h,i, Calculated bandgap central frequency dependence on lattice constants a (h) and filling ratio d/a (i). j,k, Simulated sound Read More