Stretchable electronics have demonstrated tremendous potential in wearable healthcare, advanced diagnostics, soft robotics, and persistent human–machine interfaces. Still, their applicability is limited by a reliance on low-throughput, high-cost fabrication methods. Traditional MEMS/NEMS metallization and off-contact direct-printing methods are not suitable at scale. In contrast, screen printing is a high-throughput, mature printing method. The recent development of conductive nanomaterial inks that are intrinsically stretchable provides an exciting opportunity for scalable fabrication of stretchable electronics. The design of screen-printed inks is constrained by strict rheological requirements during printing, substrate–ink attraction, and nanomaterial properties that determine dispersibility and percolation threshold. Here, this review provides a concise overview of these key constraints and a recent attempt to meet them. We begin with a description of the fluid dynamics governing screen printing, deduce from these properties the optimal ink rheological properties, and then describe how nanomaterials, solvents, binders, and rheological agents are combined to produce high-performing inks. Although this review emphasizes conductive interconnections, these methods are highly applicable to sensing, insulating, photovoltaic, and semiconducting materials. Finally, we conclude with a discussion on the future opportunities and challenges in screen-printing stretchable electronics and their broader applicability.

Stress is one of the main causes that increase the risk of serious health problems. Recent wearable devices have been used to monitor stress levels via electrodermal activities on the skin. Although many biosensors provide adequate sensing performance, they still rely on uncomfortable, partially flexible systems with rigid electronics. These devices are mounted on either fingers or palms, which hinders a continuous signal monitoring. A fully‐integrated, stretchable, wireless skin‐conformal bioelectronic (referred to as “SKINTRONICS”) is introduced here that integrates soft, multi‐layered, nanomembrane sensors and electronics for continuous and portable stress monitoring in daily life. The all‐in‐one SKINTRONICS is ultrathin, highly soft, and lightweight, which overall offers an ergonomic and conformal lamination on the skin. Stretchable nanomembrane electrodes and a digital temperature sensor enable highly sensitive monitoring of galvanic skin response (GSR) and temperature. A set of comprehensive signal processing, computational modeling, and experimental study provides key aspects of device design, fabrication, and optimal placing location. Simultaneous comparison with two commercial stress monitors captures the enhanced performance of SKINTRONICS in long‐term wearability, minimal noise, and skin compatibility. In vivo demonstration of continuous stress monitoring in daily life reveals the unique capability of the soft device as a real‐world applicable stress monitor.

Modern auscultation, using digital stethoscopes, provides a better solution than conventional methods in sound recording and visualization. However, current digital stethoscopes are too bulky and nonconformal to the skin for continuous auscultation. Moreover, motion artifacts from the rigidity cause friction noise, leading to inaccurate diagnoses. Here, we report a class of technologies that offers real-time, wireless, continuous auscultation using a soft wearable system as a quantitative disease diagnosis tool for various diseases. The soft device can detect continuous cardiopulmonary sounds with minimal noise and classify real-time signal abnormalities. A clinical study with multiple patients and control subjects captures the unique advantage of the wearable auscultation method with embedded machine learning for automated diagnoses of four types of lung diseases: crackle, wheeze, stridor, and rhonchi, with a 95% accuracy. The soft system also demonstrates the potential for a sleep study by detecting disordered breathing for home sleep and apnea detection.