Bi-sided laser-induced graphene sensor with decoupled bending and stretching sensing

As joint bending deformation is a primary feature of biological motions, measuring the joint angle variations of human is crucial, especially due to its significant spatial coordinate transformation and highly variable effective strain distribution across the section. The coupled deformation mode and the remarkable strain make the precious monitor of the joint motion challenging. In this study, we designed a monolithic flexible sensor with bi-side laser-induced graphene (BS-LIG) with a decoupling capability for tension and bending deformation modes. The sensor featured a PDMS substrate with sensing units on both surfaces can eliminate the contribution of tensile strain of the neural plane on the sensing value by utilizing the difference of the two-strain data, offering a reliable data in feedbacking the value of the real-time joint angle. Benefiting from the inherent softness and stretchability of PDMS, the BS-LIG sensor can withstand a tension of over 45% and a bending deformation up to 180°. Its electrical signal changes show excellent linearity with both strain and angle. Moreover, the sensor can accurately detect signal changes under varying loading rates and demonstrates high durability. Demonstrations include monitoring the bending deformation of human fingers and wrists validated the flexible sensor’s outstanding performance and significant potential for application in wearable electronic devices.