A Self-Folding 3D Bioelectronic Micro-Cage with Dealloyed Nanoporous Electrodes for Multimodal Monitoring of Cardiac Organoids

The geometric mismatch between rigid planar microelectrode arrays (MEAs) and soft three-dimensional (3D) organoids, alongside high electrode-tissue interface impedance, limits the fidelity ofin vitrobioelectronic interrogations. We present a self-folding 3D bioelectronic micro-cage featuring dealloyed nanoporous electrodes to omnidirectionally encapsulate hiPSC-derived cardiac organoids for multimodal electrophysiological and thermal monitoring. Fabricated via a wafer-scale MEMS process, the planar SiO2/PI bilayer utilizes an intrinsic residual stress gradient to spontaneously self-assemble into a 3D conformal cage upon release. Crucially, a magnetron co-sputtered Au-Cu alloy was employed for the electrode layer. During the selective etching of the Cu sacrificial layer, simultaneous dealloying occurs, generating a high-surface-area nanoporous gold electrode structure. The scaffold achieved a predictable folding radius optimized for ~500 μm organoids. The optimized nanoporous gold electrodes exhibited significantly reduced electrochemical impedance (8.3kΩ at 1 kHz) and a massively enhanced charge storage capacity (53 mC/cm²) compared to standard bare gold. Integrated serpentine resistive sensors exhibited highly linear temperature-dependent resistance changes (R² = 0.9993), enabling on-device temperature monitoring during organoid assays. Functionally, the micro-cage recorded synchronized 3D extracellular field potentials from cardiac organoids and monitored electrophysiological responses to externally applied thermal perturbations and pharmacological agents, including Verapamil and Norepinephrine. These results demonstrate a promising MEMS-compatible platform for organoid-based electrophysiological recording, temperature monitoring, and proof-of-concept drug-response assessment.