A Wearable Indentation System for Accurately Monitoring Young’s Modulus of Soft Tissues

Tissue stiffness can reflect the development of tissue lesions, changes in muscle strength, and muscle injuries. While accurate evaluation of tissue stiffness is valuable for monitoring these conditions, it remains a significant challenge. Here we developed a wearable tissue stiffness monitoring system (WSMS) to accurately evaluate the changes of tissue’s Young’s modulus through simultaneous measuring of the contact force and contact radius of the interface between a spherical indenter and the tissue via tactile sensing array. The WSMS, with dimensions of $\mathbf{2 6 ~ m m} \times$ $\mathbf{2 3} \mathbf{~ m m} \times 23 \mathrm{~mm}$, can be secured to human body with straps to measure the Young’s modulus of tissues. The WSMS demonstrated high accuracy in detecting the Young’s modulus of five custom-made PDMS cylinders with varying stiffness, achieving an average absolute error of less than 6 kPa and an overall accuracy of $\mathbf{9 3 \%}$. The WSMS shows great potential as an effective tool for the diagnosis, evaluation, and rehabilitation monitoring of related diseases.