Reports: ND752369-ND7: 'Intelligence' of Heterogeneous Materials/Structures

Lenore Dai, PhD, Arizona State University

Environmentally responsive hydrogels hold multiple important applications. However, the functionality of these materials alone is often limited in comparison to other materials like silicon; thus there is a need to integrate soft and hard materials for the advancement of environmentally sensitive materials.  In this project periods, we demonstrated the capability of integrating a thermoresponsive hydrogel, poly(N-isopropylacrylamide),  with thin film silicon ribbons, enabling the stiff silicon ribbons to become adaptive and drivable by the soft environmentally sensitive substrate. This integration provides a means of mechanical buckling of the thin silicon film due to changes in environmental stimuli (e.g., temperature, pH). We also investigate how advanced lithographic techniques can be used to generate patterned deformation on the aforementioned integrated structures. Furthermore, we explore multilayer hybrid hydrogel structures formed by the integration of different types of hydrogels that have tunable curvatures under the influence of different stimuli. Silicon thin film integration on such tunable curvature substrates reveal characteristic reversible buckling of the thin film in the presence of multiple stimuli. These results open new opportunities for developing stretchable and intelligent devices for multiple applications.

In addition, we have developed new light sensitive hydrogels which are responsive to visible light.  We are currently in the process of understanding chemistry/structure/property/performance relationships to tune the transition point and extent of these environmentally responsive gels.  Future work will focus on integrating these soft hydrogels with hard materials.