Composite additive manufacturing for suspended microelectrode arrays: Advancing oriented myocardial tissue culturing and electrophysiological sensing.

Microelectrode arrays (MEAs) have ushered in a new era of in vitro drug screening and cardiotoxicity evaluation. However, the morphological constraints of two-dimensional (2D) planar culture and the mechanical rigidity of conventional electrodes hinder the formation of myocardial tissues that closely resemble native physiological conditions and limit the accuracy of drug efficacy analysis based on electrophysiological signals. Here, we present a flexible MEA platform enabled by a composite additive manufacturing approach, with key steps including melt electrowriting of microfibers, electrostatic spraying of insulation layer, and electrospinning of nanofiber scaffolds. This design integrates suspended, flexible microfiber electrodes with tightly adhered nanofiber scaffolds, creating a 3D ordered culture environment for myocardial tissue culture while ensuring adaptable electrophysiological signal recording. The aligned nanofiber scaffolds promote oriented myocardial growth and enhance sarcomere length by 29 % compared to random fibers, resulting in a propagation speed of 15.835 cm/s. The flexible and stretchable microfiber electrodes, approximately 20 μm in diameter, conform dynamically to tissue deformation during beating. Furthermore, the platform's functional performance is validated using isoproterenol and verapamil, confirming its potential for on-chip drug screening applications. These results highlight the promise of the suspended, flexible, and aligned MEAs for on-chip drug screening.