Techniques for surface charge measurements and exploring contact electrification

Contact electrification (CE) is one of the most important physical phenomena within the realm of surface science, with a history spanning over 2,600 years. Although numerous experiments have been conducted to detect CE and theories regarding electron, ion, and material transfer have been proposed, the mechanism of CE remains a subject of ongoing debate and continues to intrigue scientists. A key issue in CE studies is accurately measuring the charge transfer in various situations. The development of charge transfer measurements has consistently led to a deeper understanding of CE. In this review, we explore the field of CEs, focusing on methods for measuring charge transfer. The introduction of six experimental methods from macroscopic to microscopic and first-principles calculations for CE studies aims to promote their proper use and inspire the design of new methods. Moreover, we highlight the shortcomings of the present research approach and provide a perspective on future methodological developments.