Imagine building a tiny, squishy playground for cells — and then, with the flip of a switch, making it stiffer or softer without ever touching it. That's exactly what Jae Park, a doctoral student at Washington University in St. Louis, has created.
Park, working in the lab of biomedical engineering professor Alexandra Rutz, developed a 3D scaffold made from a special electricity-conducting material called PEDOT:PSS. When he applied small amounts of voltage, the scaffold changed its stiffness — and when he turned the electricity off, the stiffness shifted again over the following hours. The biggest change he observed was 32.5 percent. Smaller voltage adjustments of just 0.2 volts produced stiffness changes between 6.7 and 10.4 percent. Even after he removed the voltage entirely, the material continued to slowly shift in stiffness over 24 hours, changing by anywhere from 2.6 to 15.2 percent.
Why does this matter? Stiffness plays a role in some serious health conditions. When tissues become too stiff, it can contribute to fibrosis — a hardening of organs that can lead to lung, liver, or heart problems. Stiff environments are also linked to the spread of certain cancers. Until now, researchers studying how stiffness affects cells had to use static materials, meaning they could only test one firmness at a time. But cells in the human body don't live in a world of just "soft" or "stiff." Everything is constantly shifting.
"An emerging need in mechanobiology is to move past static stiffness and have a material to which you can apply different stiffness states to the same cell or tissue because then we can ask different biological questions," Rutz said. She points to questions like: If a cell moves from a soft environment to a stiff one and back again, does it change permanently? Or does it remember its original softness and bounce back?
The new platform opens the door to answering those questions. Because the material is also electronically conducting, it could one day be combined with other electronics to create high-throughput systems — meaning scientists could test thousands of cells or conditions at once. Park says he was surprised by how precisely the stiffness responded to voltage, expecting a simple one-to-one relationship but finding something more complex and interesting.
The research was published in the journal Advanced Functional Materials. The team sees potential for this technology to eventually help scientists better understand fibrosis, cancer, and other diseases driven by mechanical changes in the body — and maybe, someday, contribute to treatments.