Flexible ionic pressure sensors: From migration-electronic mechanisms to emerging iontronic paradigms

Abstract

Flexible ionic pressure sensors (FIPS) have emerged as promising candidates for bridging the gap between electronics and biologically compatible interfaces. Unlike previous reviews, which focused primarily on materials or devices, this review presents a classification of FIPS based on mechanisms into two distinct categories: the migration-electronic type and the emerging iontronic type. Eight representative sensing mechanisms are systematically analyzed, including ionic piezoresistive, capacitive, piezoelectric and triboelectric effects (migration-electronic), as well as ionic diode, potentiometric transduction, nanofluidic and coupled nanofluidic–potentiometric transduction mechanisms (emerging iontronic). The basic force-electric response principles of each type of sensor have been described, combining theoretical derivation formulas followed by a comparative analysis of advantages, disadvantages, and key performance indicators, which have both comprehensiveness and originality. Furthermore, we highlight advanced engineering approaches integrating ionic transport materials, flexible substrates, and novel electrodes to enhance sensitivity, stability, and multi-modal responsiveness. Finally, we outline current challenges and future prospects of wearable electronics, healthcare monitoring, and intelligent robotics. By mapping the evolution of sensing mechanisms and their associated architectures, this review provides a comprehensive and forward-looking perspective on the development of next-generation ionic sensing systems.