Aerosol Jet® Printing on stereolithography resin substrates for in-vitro dual bioreactor sensing

Abstract

Aerosol Jet® Printing (AJ®P) is a relatively novel additive manufacturing technique, of the type direct writing, principally applied for printed electronics. Particularly, AJ®P has the ability to print various functional inks (conductive, dielectrics, biological solutions) at micro-scale resolution and on free-from substrates. This work investigates AJ®P to fabricate conductive patterns on stereolithography (SLA) samples towards the development of an innovative bioelectrical device for in-vitro dual bioreactor sensing. Silver nanoparticle (AgNPs) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) inks were both tested. Preliminary results show a low metal-polymer AgNPs-SLA interaction, revealing the presence of pores and cracks along with the printed pattern after thermal sintering, with no electrical resistance (R) detected. In contrast, the PEDOT:PSS ink reveals a good covering of the SLA samples, with R decreasing with the number of printed layers (from ~700 KΩ to ~60 Ω for 15 and 40 layers, respectively, on lines 1 cm long). However, using the PEDOT:PSS ink, the total printing time was ~45 minutes, hence not ideal for an industry-oriented vision. Therefore, a study on the optimization of the AgNPs-SLA sample interaction was carried out. SLA samples were coated with Parylene-C (ParC), and further treated with a low pressure plasma. The final results show excellent conductivity (R~2.40 Ω), with a printing time of ~5.5 minutes (7 layers), demonstrating the possibility to obtain a functional circuit. Eventually, the circuit was encapsulated with polydimethylsiloxane (PDMS) in order to avoid a release of Ag+ ions, potentially toxic in the medium culture.