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Soft active materials and soft machines
Machines in engineering use mostly hard materials, while machines in nature are often soft. This difference has been an inspiration for the nascent field of soft machines. What does softness impart to the life of animals and plants ? Softness enables large deformation, which in turn provides vital functions. Familiar examples include the beating of the heart, the sound shaped by the vocal folds, and the accommodation of the eye. In soft machines, deformation of soft materials is used to provide functions such as regulating flow in microfluidics, modulating light in adaptive optics, and interfacing tissues with stretchable electronics. Soft materials can deform in response to stimuli other than mechanical forces. Dielectric elastomers deform under voltage. Hydrogels swell in response to changes in humidity, pH, temperature, and concentration of salt. How do mechanics and chemistry work together to generate large deformation ? How do molecular processes and geometric layouts affect functions of devices ? How efficiently can materials convert energy from one form to another ? These questions are stimulating new and exciting developments. This lecture highlights theory and experiments of soft materials that enable the creation of soft machines.