We’re taking advantage of a polymeric composite’s response to light to generate position-specific and time-dependent forces that cells normally experience, from the relatively simple traction/compression forces to the more complex ones. Serving as a dynamic scaffold, the effect of physical force on cell differentiation can be revealed. Because the same substrate can generate different types of forces at different locations, we can investigate the side-by-side effects of different force types on cells on the same substrate.

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The nanocomposite bilayer system that we’ve designed and fabricated is comprised of few-walled carbon nanotubes (FWCNTs) that are uniformly distributed and covalently connected to thermally-responsive poly(N-isopropylacrylamide). It forms the 1.5-mm-thick bottom layer that responds to near infared light. To complete the substrate, we topped it with a cell-seeding layer of approximately 0.15 mm thickness and comprised of collagen functionalized poly(acrylic acid)-co-poly(N-isopropylacrylamide), which interpenetrates into the bottom layer.

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Covalent-coupling of all the components and uniform distribution of FWCNTs leads to large and fast mechanoresponses. For example, we’ve produced a 50 % change in mechanical strain in the substrate at the point of NIR stimulation of about 1 Hz and 0.02 wt % FWCNTs. We have further demonstrated that the mechanical strain imposed by NIR stimulation can be transmitted onto cells. Human fetal hepatocytes can change shape without signs of detriment on cell viability.

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To the best of our knowledge, we’ve created a platform that’s the first ever to harness nanotechnology to generate fast and controlled mechanical forces to actuate cells.