Digital Light 3D Printing of PEDOT-Based Photopolymerizable Inks for Biosensing

Abstract

3D conductive materials such as polymers and hydrogels that interface between biology and electronics are actively being researched for the fabrication of bioelectronic devices. In this work, short-time (5 s) photopolymerizable conductive inks based on poly(3,4-ethylenedioxythiophene) (PEDOT):polystyrene sulfonate (PSS) dispersed in an aqueous matrix formed by a vinyl resin, poly(ethylene glycol) diacrylate (PEGDA) with different molecular weights ( M n = 250, 575, and 700 Da), ethylene glycol (EG), and a photoinitiator have been optimized. These inks can be processed by Digital Light 3D Printing (DLP) leading to flexible and shape-defined conductive hydrogels and dry conductive PEDOTs, whose printability resolution increases with PEGDA molecular weight. Besides, the printed conductive PEDOT-based hydrogels are able to swell in water, exhibiting soft mechanical properties (Young’s modulus of ∼3 MPa) similar to those of skin tissues and good conductivity values (10 –2 S cm –1 ) for biosensing. Finally, the printed conductive hydrogels were tested as bioelectrodes for human electrocardiography (ECG) and electromyography (EMG) recordings, showing a long-term activity, up to 2 weeks, and enhanced detection signals compared to commercial Ag/AgCl medical electrodes for health monitoring.

Advances in Bioelectrode Design for Developing Electrochemical Biosensors

“…Therefore, DLP takes less time than SLA to form the 3D structure. A photopolymerizable conducting ink for fabricating bioelectrodes for human electrocardiography (ECG) and electromyography (EMG) was developed . The ink contains dispersed PEDOT:PSS in poly­(ethylene glycol) diacrylate (PEGDA), ethylene glycol (EG), and a photoinitiator.…”

3D Printed Electromyography Sensing Systems

“…DLP printing uses liquid resin to create plastic objects layer by layer, cured by UV light from a digital light projector. [60] While conductive 3D printing using DLP is challenging, Lopez-Larrea et al [61] were able to develop 3D-printed hydrogels with conductive inks using poly (3,4-ethylenedioxythiophene) (PEDOT). The printed hydrogels demonstrated high conductivity and long-term reproducible detection of EMG recording.…”

Imparting High Conductivity to 3D Printed PEDOT:PSS

“…5−7 Furthermore, even at short chain length, CPs absorb strongly in the ultraviolet and visible wavelength range, 8,9 hindering photoinitiation in light-based 3D printing methods such as stereolithography (SLA) and digital light processing (DLP). 10 A number of methods, primarily utilizing composite materials or secondary networks, have been used to generate 3D structures with CPs. 11−16 However, the electrical properties of the resulting materials are generally poor due to the insulating additives or chemical modification that improve printability but reduce conductivity.…”

“…This is mainly due to the delicate nature of CPs, which are sensitive to chemical, thermal, and processing conditions . The electron-rich nature of CPs makes them prone to irreversible oxidation or decomposition at elevated temperatures, rendering them incompatible with 3D printing mechanisms such as fused deposition modeling (FDM) or selective laser sintering (SLS), which rely on elevated temperature to produce parts from molten or semimolten polymers. − Furthermore, even at short chain length, CPs absorb strongly in the ultraviolet and visible wavelength range, , hindering photoinitiation in light-based 3D printing methods such as stereolithography (SLA) and digital light processing (DLP) …”