Magnetically Reshapable 3D Multi-Electrode Arrays of Liquid Metals for Electrophysiological Monitoring of Brain Organoids

Brain organoids have emerged as a miniaturized substitute for the human brain to investigate the electrophysiological developments and mechanisms in three-dimensional (3D) neural network circuits. To comprehend the volumetric neural connectivity of a brain organoid, it is crucial to monitor the spatiotemporal electrophysiological signals within the organoid, known as intra-organoid signals. However, previous methods risked damaging the 3D cytoarchitecture of organoids, either through sectioning or inserting rigid needle-like electrodes. Also, the limited numbers of electrodes in fixed positions with non-adjustable electrode shapes were insufficient for examining the complex neural activity throughout the organoid.<br/>Herein, we present a magnetically reshapable 3D multi-electrode array (MEA) using direct printing of liquid metals for electrophysiological analysis of brain organoids. The adaptable distribution and the softness of these printed electrodes facilitate the spatiotemporal recording of intra-organoid signals. The height of these liquid 3D probes is controllable to monitor electrophysiological signals from entire 3D spatial points in the organoid. Furthermore, the unique capability to reshape these soft electrodes within the organoid using magnetic fields allows a single electrode in the MEA to record from multiple points, effectively increasing the recording site density without the need for additional electrodes. This multi-spot detectable MEA can be advantageous for the 3D mapping of intra-organoid neural networking circuitry, and it offers a promising solution to overcome the limitations of previous methods and providing elaborate insights into the electrophysiological volumetric networks of brain organoids.