High‐Density Electronic Integration for Wearable Sensing

Wearable electronics integrated into clothing are of growing interest for sensing and radio‐frequency (RF) communication and also for connectivity with mobile wireless devices. This chapter discusses E‐fiber‐based conductive surfaces and briefly considers the conductive ink technology. It presents two examples, where the circuits and antenna fabricated using embroidery of conductive fibers were used to develop power‐harvesting circuits. In the first example, wirelessly transmitted power from a source was collected in its far field, whereas in the second example, RF power was transferred from a transmitter to a receiver fabric‐integrated circuit using near‐field power transfer modality. Choice of dielectric substrates is also important for flexible RF antennas and circuits because this choice directly affects the electromagnetic loss performance as well as mechanical robustness of the flexible electronic substrates. The chapter describes the fabrication advances that lead to miniaturization and continuous improvement in high‐density package integration.