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Engineers at Washington University in St. Louis have developed an innovative additive manufacturing method that combines collagen, the most abundant protein in the human body, with a conductive polymer to produce bioelectronic devices that integrate more naturally with living tissue.
Collagen accounts for roughly 30 percent of the body's total protein and provides structure, strength, and elasticity to skin, bones, and soft tissues. Tianran Liu, a doctoral student in the lab of Alexandra Rutz, assistant professor of biomedical engineering at the McKelvey School of Engineering, led the project. The findings were published online on August 19 in ACS Applied Materials & Interfaces.
The team began with PEDOT:PSS, an electrical conducting polymer, and added PEGDE, a chemical compound that enables PEDOT:PSS to gel at room temperature, to create a printable ink. Liu then used a 3D printer to deposit the ink onto a collagen substrate instead of conventional glass or plastic. Tests showed the resulting material does not wash away in water; when water is added, it forms a hydrated film with stiffness comparable to soft tissue. Cells attached well to the material, remained alive, and continued to grow over time.
'This kind of material can easily wrap around very small diameters and can be handled with forceps, so it has high surgical potential,' Rutz said. 'The main benefit of collagen is bioactivity, besides those nice mechanical properties that are tissue-like. We have been thinking about applications that leverage that, such as seeding cells directly onto the device or when implanting it, so the host cells can interact with it.'
According to Rutz, the fabrication method could be used for in vitro or in vivo applications, including impedance sensors and nerve stimulators.
In a parallel advance, Liu applied the technique using cacao butter, a vegetable fat extracted from cacao beans, as a sacrificial material shaped into a specific design, embedded, and later dissolved to leave a patterned layer. Many sacrificial materials in the literature require high temperatures for removal, which would 'cook' the delicate collagen substrate. To overcome this, the team turned to an ingredient familiar from chocolate making.
'We wanted a material that we could remove at a mild temperature but also retain its shape during evaporation, so we came up with the idea to use ingredients commonly seen in chocolate,' Liu said. 'We saw videos of people 3D printing chocolate for food, and we knew that we could print the cacao butter into the 3D pillars that could be easily removed with warm water and maintain shape while drying.'
Liu said the next steps focus on the sensing component of the bioelectronic device. 'What we are learning for this kind of technology is to be able to use this kind of bioelectric material to support a tissue model, while also trying to monitor them in their natural state,' she said. 'The long-term idea is to be able to combine the two aspects, to be able to sense the functional aspect of tissue models while they are situated in this soft and bioelectronic material.'
The full citation is: Liu T, Park J, Okafor SS, Montgomery SK, Goestenkors AP, Semar BA, Alvarez RM, O'Hare CP, Wu Y, Yu JS, Vargas Espinoza CJ, Rutz AL. Additive manufacturing of PEDOT:PSS electrodes on collagen substrates for soft and bioactive electronics. ACS Applied Materials & Interfaces, published online Aug. 19, 2026. DOI: https://doi.org/10.1021/acsami.6c09421
The research was supported with funding from the National Science Foundation (CBET #2443128 and CISE #2319060 to Rutz); CMMI #15-48571 to the Center for Engineering MechanoBiology; and Washington University in St. Louis through the Women's Health Technologies Collaboration Initiation Grant, Center for Regenerative Medicine Seed Grant, Ovarian Cancer Research Innovation Fund Award, and the McDonnell Center for Cellular and Molecular Neurobiology Small Grant. T. Liu and A. Rutz are inventors on a U.S. patent application that covers the additive manufacturing of extracellular matrix encapsulated conducting polymer electrodes.
Source: Mirage News