Fig. 4: Wearable and implantable electromechanical devices with tissue-mimicking stretchability.

a Schematics of an omnidirectionally stretchable piezoelectric NG fabricated by integrating the DL-alanine network with a stretchable Ag NWs electrode. Top inset: a SEM image of percolated Ag NWs. Bottom inset: digital images of a stretchable piezoelectric NG. b The voltage outputs measured from the stretchable NG without strain and with 20% tensile strains along various directions in response to 1 Hz pressure oscillation ( ~ 156 kPa). c A plot of average peak-to-peak voltage outputs as a function of the strain direction. n = 5 for each group. The error bars represent standard deviations. All data in Fig. 4c are presented as mean ± s.d. d The conformal attachment of a stretchable NG on human hand knuckles when fingers were bent and released (left). The stable voltage output under repeating finger bending (middle), and different voltage outputs in respond to different degrees of finger bending (right). e Implantation of a stretchable NG on the top thigh muscle of a swine (left), and its in vivo piezoelectric voltage outputs under different leg movements: (i) swing; (ii) lifting; (iii) rotating.