Recent advances and key opportunities on in-plane micro-supercapacitors: From functional microdevices to smart integrated microsystems

The popularization of portable, implantable and wearable microelectronics has greatly stimulated the rapid development of high-power planar micro-supercapacitors (PMSCs). Particularly, the introduction of new functionalities (e.g., high voltage, flexibility, stretchability, self-healing, electrochromism and photo/thermal response) to PMSCs is essential for building multifunctional PMSCs and their smart self-powered integrated microsystems. In this review, we summarized the latest advances in PMSCs from various functional microdevices to their smart integrated microsystems. Primarily, the functionalities of PMSCs are characterized by three major factors to emphasize their electrochemical behavior and unique scope of application. These include but are not limited to high-voltage outputs (realized through asymmetric configuration, novel electrolyte and modular integration), mechanical resilience that includes various feats of flexibility or stretchability, and response to stimuli (self-healing, electrochromic, photo-responsive, or thermal-responsive properties). Furthermore, three representative integrated microsystems including energy harvester-PMSC, PMSC-energy consumption, and all-in-one self-powered microsystems are elaborately overviewed to understand the emerging intelligent interaction models. Finally, the key perspectives, challenges and opportunities of PMSCs for powering smart microelectronics are proposed in brief.