Motivation/Inspiration/Background: Composite materials are ubiquitous in nature. The sea cucumber dermis’ adaptive mechanical behavior is a defense mechanism that is enabled by a soft matrix which is reinforced with stiff collagen fibrils. The tissue stiffness is regulated by altering fibrillar interactions, and thereby the degree of stress transfer across the fibrils, via locally secreted compounds. The squid beak is a nanocomposite that is composed of a fibrous chitin network and a crosslinked protein matrix. The beak has a water-activated mechanical gradient that has evolved to act as a bridge between the stiff beak tip and the soft connecting tissues. The mechanical gradient of the beak correlates with a change in the cross-linking and fiber density along the beak. Plants employ cellulose fiber-based composites to achieve actuation that result in, e.g. pinecone opening or plant awns that aid seed dispersal, via humidity-induced differential swelling mechanisms.
Proposed Work: The goal of this project is to expand our bio-inspired CNC nanocomposites platform to access new materials that will have applications as active implants and deployable 3D structures, inspired by the squid beak and the humidity-induced differential swelling/actuation of plants. We will use greyscale photolithography (GSPL) in combination with our previously developed photo-reactive nanocomposites to access 3D variation in film functionalization. By exploiting localized intensity modulation using specially-designed photomasks, GSPL (Figure 1a) can create contoured 3D structures in conventional photoresists that can be used as etch masks to create micro–lenses, microturbine blades, and tapered structures in silicon. We propose to use GSPL to selectively expose our UV-reactive nanocomposites (e.g. via thiol-ene chemistry) to create 3D gradients in functionalization/crosslinking, yielding material property gradients (Figure 1b). GSPL will enable the fabrication of miniature 3D, stimuli-responsive structures with feature sizes and material property domains as small as 1 μm. This work will be complemented by efforts in Switzerland (Weder), combining the effects of water-triggered actuation/softening and shape memory.
Lead PIs: Jeffrey Capadona, Stuart Rowan, Christoph Weder
Faculty Collaborators: Agata Exner, Mark Griswold, Mike Hore, Horst von Recum, Chris Zorman
Graduate Students: Sydney Song, Yefei Zhang, Charlie Lindberg, Livius Muff, Baptiste Monney
Undergraduate Students:
