Flowable Approach for the Formation of Biomaterial Sheets

Nature routinely uses a bottom – up approach for the organization of materials arounds us. This unique structural and hierarchical organization spans seven orders of magnitude in length scale: from molecular (~ nm) to organ dimensions (~ cm) is a hallmark of many organs. The variation in the structural organization imparts different functionalities and macroscopic properties such as elasticity, permeability, and optical transparency to tissues. Tissue – engineering routinely uses several promising strategies to engineer tissues that mimic the complex architecture and functionality of native tissues. However, some of their limitations include the inability to recapitulate the hierarchical assembly of materials, tunability of nanoscale properties, lack of scalability, and time – consuming fabrication methods. In this thesis, we have developed two microfluidics – enabled approaches for the scalable formation of fibrillar and polysaccharide – based hierarchical soft materials with precise control over the material composition, geometric and mechanical properties, cellular response, and structural assembly. In the first approach, we adopted a microfluidic strategy for the continuous formation of centimeter – wide, ultrathin collagen sheets. Application of shear via hydrodynamic flow – focusing through a geometric constriction and strain – induced pulling by a rotating mandrel, and the osmotic and evaporation – induced removal of water resulted in anisotropically aligned and compacted sheets with ultimate tensile strengths of 0.5 – 2.5 MPa and elastic moduli of 3 – 36 MPa. We used multi – lamellar collagen sheets to produce tissue – engineered vascular grafts with biomechanical properties similar to native vessels. The collagen sheets were also used as transwell – membranes for drug screening purposes. Human bronchial epithelial cells showed a high trans – epithelial resistance of 1900Ω x cm2. F508del – CFTR cells showed a three – fold increase in chloride conductance when treated with Cystic Fibrosis Trans –Regulator corrector, lumacaftor (VX – 809). The second microfluidic strategy allowed the continuous preparation, and processing of meter – long, roll – to – roll processed biomaterial sheets with control over thickness, morphology, and elastic properties. 3D structures with deterministic and stochastic voids were produced using layer – by – layer folding and stacking techniques. The approaches presented here find application in areas such as tissue engineering, regenerative medicine, drug – screening, and biohybrid devices.

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