Electronic Skin Devices Transform Continuous Vital Signs Monitoring

As populations age and chronic disease burdens rise globally, the need for continuous, unobtrusive health monitoring has never been greater. Traditional clinical devices for measuring heart rate, blood pressure, and blood oxygen are bulky, expensive, and require trained operators—making them impractical for daily home use or deployment in underserved regions. This review from Nanjing University provides a bottom-up, comprehensive overview of skin-inspired electronic (e-skin) devices designed to fill this gap, covering materials, wireless communication, data processing, and medical applications.

The review organizes the material landscape into three primary categories. Nanomaterials—including zero-dimensional quantum dots and gold nanoparticles, one-dimensional silver nanowires and carbon nanotubes (CNTs), and two-dimensional graphene and MoS₂—offer tunable electrical conductivity, mechanical flexibility, and biocompatibility. Silver nanowires, prepared via liquid polyol or self-assembly methods, have been fashioned into microcracked pressure sensors with sensitivities reaching 1167 kPa⁻¹, capable of detecting subtle carotid artery pulse and respiratory rate changes simultaneously. CNTs dispersed on ultrathin fibrous grids enable conformal skin attachment for non-invasive electrophysiological and temperature monitoring. Graphene, now producible in large-area films via chemical vapor deposition, has been integrated into micro-supercapacitors with energy densities up to 34.1 mWh/cm³ to power wireless pressure sensors.

Conductive hydrogels represent a second major material class, prized for their tissue-mimicking mechanical properties, high water content, and ionic conductivity that closely resembles biological tissue. Liquid metals—particularly gallium-based alloys—complete the triad, offering exceptional stretchability and electrical conductivity while remaining fluid at room temperature, enabling conformal interconnects and electrodes that maintain function under extreme deformation.

Wireless data transmission is identified as a critical bottleneck. The review surveys RFID, near-field communication (NFC), and Bluetooth Low Energy (BLE) protocols as bridges between e-skin sensors and smartphones or tablets. NFC enables battery-free operation through energy harvesting, while BLE supports higher data rates for multimodal signal streams. The authors emphasize that resolving the tension between device flexibility and reliable wireless performance is essential for practical deployment.

On the data processing front, the review highlights the growing role of machine learning and AI algorithms in extracting clinically meaningful information from raw wearable sensor streams—enabling detection of arrhythmias, blood pressure trends, and respiratory anomalies from signals that would otherwise require specialist interpretation. Medical application domains covered include cardiovascular monitoring (ECG, pulse wave, blood pressure), respiratory monitoring, body temperature surveillance, and blood oxygen (SpO₂) sensing via flexible photoplethysmography. The authors conclude that while proof-of-concept demonstrations are impressive, key challenges remain: long-term skin biocompatibility, stable adhesion through sweat and motion, power autonomy, and regulatory pathways to clinical adoption.