Biofabrication of high aspect ratio, flexible, and bioconductive micropillar arrays of PEDOT:PSS composite for 3D printed bioelectronics

The next generation of three-dimensional (3D) micro-additive manufacturing (AM) bioelectronics requires inks that simultaneously combine high electrical conductivity, biocompatibility, electrochemical stability, and compatibility with 3D processing. However, most existing inks fail to meet all these criteria, with processability and repeatability remaining major bottlenecks. This challenge is particularly serious in printed electronics technologies, such as Aerosol Jet® Printing (AJ®P), for which commercially available formulations tailored to specific applications are still scarce. Here, we present a novel poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-based ink incorporating polyethylene glycol, ethylene glycol, and carboxymethyl cellulose to obtain a composite that fulfils all requirements, being conductive, processible by AJ®P and biocompatible. The formulation exhibits high conductivity (<i>σ</i>= 495.29 S · cm^-1), electrochemical stability, and biocompatibility with both human fibroblasts and iPSC-derived neural stem cells. Its low viscosity (<i>μ</i>= 7.93 mPa · s) enables precise and repeatable AJ®P fabrication while supporting controlled, high-resolution 2D patterning and 3D microfabrication with aspect ratios up to 9. Dense or hollow microarrays of 24 flexible pillars (diameter ⩾ 35<i>μ</i>m; elastic modulus = 3.1 × 10⁶Pa per pillar) can be fabricated within 10 min, without masks or supporting materials. This work focuses on the material and process optimisation study of a customisable bioink for AJ®P in 3D micro-AM bioelectronics, with potential applications in 3D microelectrode arrays, biosensors, tissue engineering.