The e-Flower: A hydrogel-actuated 3D MEA for brain spheroid electrophysiology
Eleonora Martinelli, Outman Akouissi, Luca Liebi, Ivan Furfaro, Desirée Maulà, Nathan Savoia, Antoine Remy, Laetitia Nikles, Adrien Roux, Luc Stoppini, Stéphanie P. Lacour
Abstract
Traditional microelectrode arrays (MEAs) are limited to measuring electrophysiological activity in two dimensions, failing to capture the complexity of three-dimensional (3D) tissues such as neural organoids and spheroids. Here, we introduce a flower-shaped MEA (e-Flower) that can envelop submillimeter brain spheroids following actuation by the sole addition of the cell culture medium. Inspired by soft microgrippers, its actuation mechanism leverages the swelling properties of a polyacrylic acid hydrogel grafted to a polyimide substrate hosting the electrical interconnects. Compatible with standard electrophysiology recording systems, the e-Flower does not require additional equipment or solvents and is ready to use with preformed 3D tissues. We designed an e-Flower achieving a curvature as low as 300 micrometers within minutes, a value tunable by the choice of reswelling media and hydrogel cross-linker concentration. Furthermore, we demonstrate the ability of the e-Flower to detect spontaneous neural activity across the spheroid surface, demonstrating its potential for comprehensive neural signal recording.