Material and Design Strategies of Soft Microelectrode Arrays for Implantable Cardiac Interfaces.

Cardiovascular diseases (CVDs) remain one of the leading causes of mortality worldwide. However, conventional diagnostic and therapeutic technologies are often bulky, limited in functionality, and lack the mechanical softness required for continuous high-fidelity monitoring and treatment of patients with life-threatening cardiac conditions. In recent years, advances in materials science, device engineering, and system integration have led to the development of mechanically compliant microelectrode arrays (MEAs) capable of monitoring and modulating cardiac electrical, optical, and mechanical activities in vivo. These MEAs serve as promising bioelectronic platforms for conformal interfacing with the heart, monitoring cardiac physiology, and treating CVDs. This Review summarizes recent advances in soft implantable cardiac MEAs. We begin by introducing the fundamental principles of cardiac electrophysiology, followed by a detailed discussion of material candidates used in soft cardiac microelectrodes. We then review state-of-the-art cardiac MEAs for electrophysiological mapping and electrotherapy. Transparent and bioresorbable cardiac MEAs are elaborated. We further discuss multimodal devices that integrate electrical, optical, and mechanical functionalities for studying cardiac electrophysiology, optophysiology, and mechanophysiology. Finally, we highlight future directions that will advance soft cardiac MEAs toward next-generation cardiovascular diagnosis, monitoring, and therapy.