2 research outputs found
From Microscale Variations to Macroscopic Effects: Directional Actuation, Phase Transition, and Negative Compressibility in Microfiber-Based Shape-Morphing Networks
Two-dimensional shape-morphing networks are common in biological systems and
have garnered attention due to their nontrivial physical properties that
emanate from their cellular nature. Here, we present the fabrication and
characterization of inhomogeneous shape-morphing networks composed of
thermoresponsive microfibers. By strategically positioning fibers with varying
responses, we construct networks that exhibit directional actuation. The
individual segments within the network display either a linear extension or
buckling upon swelling, depending on their radius and length, and the
transition between these morphing behaviors resembles Landau's second-order
phase transition. The microscale variations in morphing behaviors are
translated into observable macroscopic effects, wherein regions undergoing
linear expansion retain their shape upon swelling, whereas buckled regions
demonstrate negative compressibility and shrink. Manipulating the macroscale
morphing by adjusting the properties of the fibrous microsegments offers a
means to modulate and program morphing with mesoscale precision and unlocks
novel opportunities for developing programmable microscale soft robotics and
actuators
Performance Fabrics Obtained by In Situ Growth of Metal-Organic Frameworks in Electrospun Fibers
Metal–organic frameworks (MOFs) exhibit an exceptional surface area-to-volume ratio, variable pore sizes, and selective binding, and hence, there is an ongoing effort to advance their processability for broadening their utilization in different applications. In this work, we demonstrate a general scheme for fabricating freestanding MOF-embedded polymeric fibers, in which the fibers themselves act as microreactors for the in situ growth of the MOF crystals. The MOF-embedded fibers are obtained via a two-step process, in which, initially, polymer solutions containing the MOF precursors are electrospun to obtain microfibers, and then, the growth of MOF crystals is initiated and performed via antisolvent-induced crystallization. Using this approach, we demonstrate the fabrication of composite microfibers containing two types of MOFs: copper (II) benzene-1,3,5-tricarboxylic acid (HKUST-1) and zinc (II) 2-methylimidazole (ZIF-8). The MOF crystals grow from the fiber’s core toward its outer rims, leading to exposed MOF crystals that are well rooted within the polymer matrix. The MOF fibers obtained using this method can reach lengths of hundreds of meters and exhibit mechanical strength that allows arranging them into dense, flexible, and highly durable nonwoven meshes. We also examined the use of the MOF fiber meshes for the immobilization of the enzymes catalase and horse radish peroxidase (HRP), and the enzyme-MOF fabrics exhibit improved performance. The MOF-embedded fibers, demonstrated in this work, hold promise for different applications including separation of specific chemical species, selective catalysis, and sensing and pave the way to new MOF-containing performance fabrics and active membranes