Fig. 2: Structural of the flexible skin socket and performances for the connection between skin sockets and the on-skin component’s LM plugs (soft-soft connection).

a The flexible skin socket has a three-layer structure. The PDMS layer’s thickness affects the socket’s adhesion and conduction. EDS surface element analysis illustrates the microscopic conduction mechanism of the flexible skin socket. Similar results were obtained from 10 independent replicate experiments. Scale bar, 20 μm. b Relationship curve between conduction resistance of the connection and PDMS dip coating concentration. Error bars are s.d. from 5 device samples and the central line represents the mean value. The inset on the right illustrates the measurement setup (overlapping area 2 cm width × 3 cm length). c The pressure-activated conduction mechanism of flexible skin sockets: LM micro-conductive channels are established by pressure. d The electrical and mechanical stretchability of the flexible skin socket and commercial tapes. The flexible skin socket connection showed greater average electrical (246%) and mechanical (247%) stretchability (overlapping area 2 cm width × 3 cm length). Error bars are s.d. from device samples n = 5 for this work, fabric, and Cu tape, n = 6 for Carbon tape, n = 4 for ACF. e The absolute change in resistance of different connections during the ultimate strain test. Unlike commercial tapes, the flexible skin socket connection remained stably conductive (resistance change within 15 Ω) even at 80 mm tensile length as shown in the image on the left (the origin length of all samples is 30 mm). The magnified image of the low tensile length region (0–10 mm) on the right shows the flexible skin socket connection experienced < 2 Ω change in resistance at 10 mm tensile length. f Cyclic bonding tests for the flexible skin socket connection. Three samples show stable conduction resistance during bonding and peeling cycles. g The 1000 cycles of 50% strain tensile test for the flexible skin socket connection. The fluctuation of the conduction resistance is within 0.5 Ω, and the baseline drift is about 0.4 Ω.