In Situ Nanomechanical Characterization Techniques for Soft Bioelectronic Interfaces and Their Building Blocks

Abstract

Soft bioelectronic interfaces constitute a paradigm shift for biomedical devices. High-resolution monitoring and stimulation of physiological processes in vivo are becoming possible with minimally invasive devices operated without inflicting tissue damage or discomfort over prolonged timescales. However, the development and commercialization of such interfaces still must address significant challenges. Biological tissue is subjected to continuous motion and the related device deformations can easily trigger fracture or delamination of the device components, putting long-term durability of soft implants at risk. In this review, an overview of experimental techniques for testing mechanical properties and failure mechanisms of soft bioelectronic devices at the nanoscale while the deformation takes place (in situ) is provided. Through the tensile test, bending test, nanoindentation, and micropillar compression test, precise measurements of the mechanical properties of individual building blocks and the interfaces themselves can be obtained. Such parameters are crucial to design, model, and optimize the device's performance. Then, recent examples of how this information guides design and optimization of soft bioelectronic interfaces and devices for healthcare, robotics, and human–machine interfaces is provided. Last of all, future research that is needed to fully achieve long-term soft bioelectronic interfaces for integration with the human body is discussed.