Shape-Morphing Living Composites

Stimuli-responsive polymers respond to their environment without requiring motors, sensors, or power supplies. Notably, the stimulus-response of many synthetic smart materials is derived wholly from physical properties, and as a result, these materials require powerful stimuli, such as heat, to induce shape change. By comparison, the stimulus-response of living organisms can be triggered by weak physical stimuli or specific biochemicals. We will discuss fabricating living yeast –hydrogel and bacteria-hydrogel composites capable of undergoing programmed shape change. As the cells are higher in modulus (~100×) than the gel, cell proliferation results in a macroscopic shape change of the composite. Importantly, genetic manipulation of the cells enables the stimulus that induces shape change to be controlled. For example, we will discuss composites where volume change on exposure to a single biochemical (L-histidine) is 14× higher than volume change when exposed to highly similar biochemicals (D-histidine and other amino acids). The use of this shape-changing material for future applications in drug delivery and sustainable manufacturing will be discussed.