A novel thickness-gradient electrospun nanomesh for interface-free e-skin applications

Recent advancements in lightweight, breathable, skin-conformable electrodes offer new opportunities for biomedical and healthcare applications. Challenges persist in establishing reliable connections between ultra-thin skin electrodes and thick data acquisition wires, necessitating innovative solutions to address the soft-hard and thin-thick interfacial mismatch. Current approaches often involve incorporating additional layers, increasing device fabrication complexity, and the risk of disconnection. This study introduces a novel thickness-gradient nanomesh electrode designed to eliminate the sharp interface between skin electrodes and interconnecting layers. The approach involves developing a 2-in-1 skin electrode-interconnector structure through successive electrospinning deposition of different nanofiber layers, with adjustments made to the spinneret width accordingly. The smooth gradient concept is validated through optical transmittance and scanning electron microscopy. The gradient nanomesh exhibits enhanced mechanical durability, enduring strain up to 23%, and maintains stable electrical performance over 1000 continuous strain cycles. Furthermore, rigid wires are replaced with conductive yarn sewn onto the gradient nanomesh, enabling accurate measurements of skin impedance. The versatile concept of thickness gradient can extend to other materials and further address interface issues in next-generation wearable devices.