Strain-based scanning probe microscopies for functional materials, biological structures, and electrochemical systems

Strain and electromechanical coupling are ubiquitous in nature, and exist in many processes involved in information technology, energy conversion, and biological phenomena. Strain-based scanning probe microscopy (s-SPM) techniques, especially piezoresponse force microscopy (PFM) and electrochemical strain microscopy (ESM), have emerged as powerful tools to probe and manipulate materials, structures, and systems at the nanoscale. In this review, we will present the fundamentals of s-SPM and a variety of its operational modes, introduce its applications in scientifically or technologically important functional materials, electrochemical systems, and biological structures, and discuss some of its challenges and potential opportunities. By detecting dynamic strains associated with underlying microscopic processes excited by a scanning probe, high sensitivity and unprecedented spatial resolution can be obtained, though caution must be exercised to distinguish different microscopic mechanisms, and quantitative interpretation of the s-SPM data remains challenging. We expect that s-SPM will continue to provide great insight into functional materials and structures, and will play a valuable role in the emerging field of materiomics.