Programmable Microstructure of Hydrogels through Liquid Crystals and Living Microorganisms

Abstract

Approaches to program the microstructure of hydrogels enable the control of cell-material interactions and the design of shape-changing materials. In this dissertation, we will investigate bottom-up strategies to program the structure and properties of hydrogels from chemical or biological standpoints. In the first study, we focus on synthetic approaches to program the microstructure of hydrogels through lyotropic chromonic liquid crystals (LCLCs) templating. The microstructures of resulting hydrogels polymerized in different LCLC phases are investigated. We quantify the anisotropic mechanical properties, and the anisotropic swelling properties of the resulting hydrogels. We explore the ability to spatially program the microstructure of hydrogels by spatially aligning the LCLC phase. The potential for these anisotropic hydrogels as compliant substrates to guide cell proliferation is explored. The second study discusses strategies to program the structure of hydrogels utilizing the growth of living Saccharomyces cerevisiae (baker’s yeast). We develop a new culturing protocol to grow these engineered living hydrogels using bread waste. The thermomechanical properties of the living hydrogels before and after growth are evaluated. A new patterning strategy to spatially control the cell viability inside the hydrogels, which leads to controlled growth and structure of the living hydrogels, is explored. This growth-dictated shape manufacturing through living hydrogels cultured from bread waste creates the possibility for future green manufacturing of materials. In the third study, we discover a new mechanism to design shape-reconfigurable structures by embedding hard magnetic particles and yeast in the hydrogel matrix. The design principle is based on the programmable magnetic-responsive shape transformation and the reversible growth of living materials. Magnetic living materials growing under magnetic confinement can retain the deformed shape through growth, which leads to shape manufacturing. A unique approach to recovering the locked shape is also examined. We evaluate the reversibility of the shape-changing behavior up to 5 cycles. The developed reconfigurable shape transformation strategy using magnetic living materials broadens the manufacturing toolboxes for the design and fabrication of morphing devices. Overall, advances in structure-programmable hydrogels will offer new properties, functionalities, and applications in tissue scaffolds, sustainable building materials, and soft robotics.