Multi-Signal Collecting E-Textile System for Long-Term Maternal Health Monitoring via Sponge Electrode

Stretchable and flexible health monitoring systems have great potential for improving the accuracy of predicting arrhythmias or diagnosing peripheral nervous system disorders through long-term measurements. Moreover, these systems create synergy when applied to maternal health monitoring. In many developing countries or regions with underdeveloped infrastructure, many pregnant women are unable to reach the hospital at the appropriate time for childbirth, putting both the mother and child at risk. To predict childbirth, hospitals provide tocodynamometer (TOCO) system that collects pressure signal of uterine contraction and electromyography (EMG) electrodes that collect uterine muscle contraction signals, and these electrodes provide highly accurate information. Nevertheless, these systems are large and rigid, making it difficult to wear them in a wearable form for daily use.<br/>Here, we propose an innovative approach for a wearable long-term maternal health monitoring system through integrated sponge and textile electrodes. The system consists of a soft and pliable polydimethylsiloxane (PDMS) sponge and stretchable textile electrodes coated with poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS). By adjusting the content of PEDOT:PSS and polyethylene oxide (PEO) that induce a cross-linking reaction in each electrode, we easily coated conductive ink on flexible substrates and adjusted the properties of two different types of electrodes: 1) those that respond sensitively to pressure (sponge) and 2) those that maintain stable electrical conductivity even during stretching (textile). Through this, the sponge electrode can keep the gel from drying out for a long time and drastically increase the contact area with the skin via its internal pores, achieving low contact impedance for collecting electrophysiological signals. Simultaneously, it can measure changes in resistance and capacitance in response to pressure, allowing the integration of bulky TOCO and EMG electrodes into a single small electrode that can capture both signals.<br/>Consequently, this system demonstrates lower contact impedance 4.41×10⁴ Ω cm², and an improved signal to noise ratio (SNR) up to 26.23 dB during electrophysiological signal collecting compared to flat textile electrode. In addition, it successfully collected wrist pulse signals, which are much weaker compared to uterine contraction signals. Finally, this electrode system was verified for maternal health monitoring capability through a clinical patient study. We strongly believe that this sponge electrode system can reliably monitor the health of pregnant women in everyday life.