Engineering carbon nanotubes-polydimethylsiloxane strain sensors for wearable respiratory monitoring

Abstract

Body movements occur naturally during chest or abdominal motion associated with breathing, providing an accessible physiological signal for non-invasive monitoring of various health conditions. However, developing soft, conformable sensors that can reliably transduce these low-strain deformations into stable electrical signals remains a key challenge. In this work, a flexible and stretchable strain sensor was developed by coating a conductive carbon nanotube (CNT) network onto a polydimethylsiloxane (PDMS) elastomer, enabling respiration monitoring through strain-induced changes in electrical resistance. Key fabrication parameters, including deposition method, sensing layer thickness, and the ratio of CNTs to a dispersing agent, were systematically optimized to enhance sensitivity and signal stability upon mechanical deformation. The optimized sensor exhibits rapid response and recovery time under cyclic loading conditions, enabling accurate capture of dynamic respiratory signals. The device also demonstrates stable and reproducible electrical output over repeated deformation cycles, indicating good durability for wearable applications. The sensor also shows high sensitivity in the low-strain region, which is particularly advantageous for detecting subtle physiological motions associated with breathing. This work highlights the potential of CNT–PDMS composite sensors as lightweight, conformable, and high-performance platforms for continuous respiratory monitoring and next-generation wearable health diagnostics.