Conductive fibers are core materials in textile electronics for the sustainable operation of devices under mechanical stimuli. Conventional polymer−metal core−sheath fibers were employed as stretchable electrical interconnects. However, their electrical conductivity is severely degraded by the rupture of metal sheaths at low strains. Because the core−sheath fibers are not intrinsically stretchable, designing a stretchable architecture of interconnects based on the fibers is essential. Herein, we introduce nonvolatile droplet−conductive microfiber arrays as stretchable interconnects by employing interfacial capillary spooling, motivated by the reversible spooling of capture threads in a spider web. Polyurethane (PU)−Ag core−sheath (PU@Ag) fibers were prepared by wet-spinning and thermal evaporation. When the fiber was placed on a silicone droplet, a capillary force was generated at their interface. The highly soft PU@ Ag fibers were fully spooled within the droplet and reversibly uncoiled when a tensile force was applied. Without mechanical failures of the Ag sheaths, an excellent conductivity of 3.9 × 10 4 S cm −1 was retained at a strain of 1200% for 1000 spooling−uncoiling cycles. A light-emitting diode connected to a multiarray of droplet−PU@Ag fibers exhibited stable operation during spooling− uncoiling cycles.

Semiconducting polymers are considered essential materials because of the dramatically increasing demand for deformable electronic and energy devices. However, an improvement in both the electrical conductivity and mechanical stretchability of these polymers has been challenging. In this study, we designed a composite material comprising Li-complexed poly­(3-hexylthiophene) nanofibrils (Li-P3HT) and poly­(styrene-b-butadiene-b-styrene) (SBS) as the conductive and stretchable active layers of electronic skins (e-skins). The cooling process of a P3HT/SBS solution leads to the one-dimensional growth of P3HT crystals due to strong π–π interactions between the thiophene backbones, which assists in the formation of percolation networks within the SBS matrix after spin coating. The complexation of Li+ and thiophene backbones significantly increased the hole concentration of the nanocomposites. The resulting conductivity was found to be 1.27 × 10–3 S cm–1, which is 5.7 times higher than that of pristine P3HT/SBS. Furthermore, the stretchable SBS matrix led to an excellent retention of long electrical pathways via percolated Li-P3HT nanofibrils for a strain of up to 50%. The printed Li-P3HT/SBS arrays on Ag nanowire/Ecoflex stretchable electrodes were utilized as the active layers of high-performance strain and pulse sensors.