Conductive viscoelastic polymer composites (CVPCs) consisting of conductive fillers in viscoelastic polymer matrices find numerous applications in emerging technologies such as flexible electronics, energy storage, and biochemical sensing. Additive manufacturing methods at micro- and mesoscales provide exciting opportunities toward realizing the unique capabilities of such material systems. In this paper, we study the direct-ink-writing (DIW) process of CVPCs consisting of electrically conductive additives in a poly(ethylene oxide) (PEO) matrix. We particularly focus on the deposition mechanisms of the DIW process and the influence of these mechanisms on the printed structure geometry, morphology, and functional properties. To this end, we utilized a novel practical approach of modeling the ink extrusion through the nozzles considering the non-Newtonian viscous effects while capturing the viscoelastic extensional flow (drawing) effects through the variation of the nozzle exit pressure. We concluded that inks containing higher amounts of high molecular weight (HMW) PEO exhibit drawing type deposition at high printing speeds and low inlet pressures enabling thinner, higher aspect ratio structures with ideal three-dimensional stacking. Under this deposition mechanism, the electrical conductivity of the anodic structures decreased with increasing printing speed, indicating the effect of the drawing mechanism on the printed structure morphology.

Osteoarthritis (OA) is a degenerative disease characterized by articular cartilage (AC) degradation that affects more than 30 million people in the USA. OA is managed with symptom-alleviating medications. Matrix-assisted autologous chondrocyte transplantation (MACT) is a tissue-engineered option, but current products are expensive and lack mechanical tunability or processability to match defect mechanical properties and anatomical shapes. Here, we explore the efficacy of a biocompatible hydrogel-based scaffold composed of sodium alginate, gelatin, and gum Arabic—referred to by SA–GEL–GA—to support bovine articular chondrocyte (bAChs) proliferation, pericellular matrix (PCM), and extracellular matrix (ECM) production. bAChs were grown for 45 days in SA–GEL–GA. Their viability, their live/dead status, histological staining, biochemical assays for glycosaminoglycans (GAGs) and collagen, atomic force microscopy (AFM) imaging, and immunofluorescence staining of collagen I, collagen II, aggrecan, and CD44 were assessed. We found that SA–GEL–GA was not cytotoxic, induced cellular proliferation by 6.1-fold while maintaining a round morphology, and supported ECM deposition by producing 3.9-fold more GAG compared to day 0. bAChs transformed into chondrons and produced a PCM enriched with collagen II (3.4-fold), aggrecan (1.7-fold), and CD44 (1.3-fold) compared to day 0. In summary, SA–GEL–GA supported the proliferation, ECM production, and PCM production of bAChs in vitro.