Guest Semester - Functional soft materials to interface with biology: from non-invasive mechanochemical drug delivery to miniaturized soft robotic actuators

Chemical interference remains one of the most effective means to control cellular functions and treat diseases. However, non-invasive, localized delivery and activation of chemical reactions and chemical release deep inside body is still challenging. In this talk, I will cover how soft materials with energy transduction capabilities can address these challenges. In the first part, I will showcase our efforts in developing soft materials that facilitate mechanochemistry, a chemical process initiated by mechanical stress, with biocompatible focused ultrasound assisted by acoustically-active proteins. Through acoustic cavitation seeded by genetically encoded, air-filled protein nanostructures called gas vesicles, polymers undergo bond cleavage at the designed, weakest position in backbones and thus release small molecular payloads, including fluorophores and therapeutic drugs by chemical cascade. We further demonstrate the stimulation of mechanochemistry in tissue-mimicking gels, suggesting its potential applications in remotely controlled drug release for mechano-chemo-therapy inside body. To address the challenges of targeted delivery within the body, in the second part of the talk, I will discuss the development of cell-mimicking miniaturized soft actuators based on molecularly anisotropic polymer networks made by liquid crystalline elastomers (LCEs). Magnetically controlled polymer alignment encodes stimuli-responsive, multimodal mechanical deformations in microfabricated LCEs, including shrinkage/expansion, tilting, twisting and phototropic motions. This polymeric material may find applications in untethered microrobots to navigate inside body for localized payload delivery.