Title: PROGRAMMABLE ENGINEERING OF TISSUE-LIKE ELASTOMERS
Abstract:Soft biological tissues combine oxymoronic mechanical characteristics such as softness and firmness, originated from hierarchical self-assembly of collagen fibrils linked by assorted chemical and physical bonds. Various molecular and macroscopic constructs have been explored to reproduce the individual mechanical responses of tissue; however, they fail to integrate them in one material. Recently, we have developed a universal materials design platform based on precision engineering of brush-like network architectures to encode biological mechanical properties in solvent-free elastomers. The independent variation of architectural parameters, including side-chain length and grafting density, allows independent regulation of Young’s modulus, elongation-at-break, and firmness parameter. Using a combination of molecular imaging and ultra-small X-ray scattering, we have decrypted the hierarchy of brush network organization and identified molecular mechanisms that are responsible for the initial softness and subsequent strain-stiffening of brush-like elastomers.
Further, we took advantage of myriad chain-end functionalities of brush-like network strands to assemble polymer networks that simultaneously soft, firm, elastic, and strain-rate responsive. Depending on the chemistry of side-chain ends, we can control the curing time from seconds to days, which benefits a range of biomedical applications from tissue fixation to body implants, respectively. Physical bonding also provides opportunities for adding self-healing and time-programmable functions to the tissue-like mechanics. We will discuss different principles of brush network assembly including permanent, latent, and dynamic cross-link that emulate different features of biological networks. A concept of injectable elastomers will be presented opening prospective for additive manufacturing of biomedical devices and tissue models.