Micro-3D Printed Conductive Polymer Composite via Two-Photon Polymerization for Sensing Applications

Two-photon Polymerization (2PP) process for high-resolution 3D printing presents an opportunity to design micro-scale structures with a high surface-to-volume ratio for highly responsive devices. However, these acrylate or thiol-based resins are electrically insulating and non-functional in nature, therefore limiting their widespread application in biosensing and biotechnology. Here, a novel conductive polymeric composite resin to print conductive 3D micro-structures via the 2PP technique is developed and its application in sensing are demonstrated. The composite consists of acrylate-based 2PP resin and Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), a conductive and biocompatible organic semiconductor The PEDOT:PSS incorporation in resin through Raman and X-ray photoelectron spectroscopy (XPS) is studied. An electrical conductivity of 3.5 × 10² S cm⁻¹ in a 20 µm long and 10 µm high 3D printed micro-structure which is suitable for electronic applications is achieved. An ultra-fast micro-3D printed humidity sensor with a response and recovery time of 0.15 and 0.3 s respectively is demonstrated. The printed sensors show high sensitivity in humidity levels of 0–80%RH. As a proof of concept, the real-time respiration of a human body is recorded, implying a potential application in health monitoring systems.