A salient feature of living materials is their ability to grow and evolve their structures with time. As a vital adaptation, some organisms, such as Planaria, would not only increase in size, but also shrink and reverse the growth to preserve only the parts necessary to survive in nutrient-deficient environments. In contrast, synthetic objects formed through milling, molding, assembling, printing, extruding, etc., display fixed sizes and properties. While various methods have been developed to create new dynamic constructs that change size, shape, and physical properties in response to stimuli, these materials ultimately return to their initial size and shape after reconfiguration, and their properties cannot be post-modulated after fabrication. In this talk, I will discuss our most recent work in developing a new class of “growing” polymers with the ability to controllably increase/decrease in mass and size, change multiple physical and chemical properties on-demand, and decompose when needed, mimicking the remarkable abilities of living organisms. Such “living” polymers are realized by introducing two essential biological mechanisms into the realm of synthetic materials: (1) nonequilibrium dynamic growth and (2) an osmotically driven “nutrient” supply and incorporation mechanism to support the growth. The performance of the system is orchestrated by a series of coordinated reactions, diffusion, deformation, and network remodeling. Through integrated theoretical modeling, experimental characterization and polymer synthesis, we decipher the coupled chemo-mechanical growth mechanism and explore the guiding rules toward accurate control in these materials.
