Fig. 1: 3D multi-electrode array of liquid metals as an electrophysiological monitoring platform.

a Schematic illustration of intra-organoid signal recording by 3D LM MEA. b Schematic illustration of printing system and printing process. c Various heights of 3D LM pillars by control printing velocity. Each data point indicates the average of 12 measurements, and the error bars represent the s.e.m. Inset presents SEM image, which was taken by 30° tilting of the substrate, presenting 3D LM pillars with various heights. Scale bar, 100 µm. This experiment was independently repeated more than ten times with similar results. d Optical images of LM interconnects and 3D LM pillars with height-variance. Scale bars, 100 µm. e Schematic illustrations of 3D LM MEA, and single 3D LM electrode. f SEM image of platinum nanoclusters coated on tip of the electrode (The substrate is 30° tilted when the image was taken). Scale bar, 1 µm. This experiment was independently repeated more than ten times with similar results. g Comparison of impedances between pristine 3D LM electrode and Pt nanocluster coated LM electrode (n = 9 electrodes for each group; p = 2.27 × 10⁻¹³). All data are presented as mean ± s.e.m. Statistical differences were determined with unpaired, one-sided t-test; ***p < 0.001. LM liquid metal; MEA multi-electrode array; SEM scanning electron microscopy.