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 anisotropic shape-morphing networks composed of thermoresponsive polymeric 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.

Hierarchically structured polymeric fibers, composed of structural nanoscale motifs that assemble into a microscale fiber are frequently found in natural fibers including cellulose and silk. The creation of synthetic fibers with nano-to-microscale hierarchical structures represents a promising avenue for the development of novel fabrics with distinctive physical, chemical, and mechanical characteristics. In this work, we introduce a novel approach for creating polyamine-based core–sheath microfibers with controlled hierarchical architectures. This approach involves a polymerization-induced spontaneous phase separation and subsequent chemical fixation. Through the use of various polyamines, the phase separation process can be manipulated to produce fibers with diverse porous core architectures, ranging from densely packed nanospheres to segmented “bamboo-stem” morphology. Moreover, the nitrogen-rich surface of the core enables both the chemisorption of heavy metals and the physisorption of proteins and enzymes. Our method offers a new set of tools for the production of polymeric fibers with novel hierarchical morphologies, which has a high potential for a wide range of applications such as filtering, separation, and catalysis.

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.

Fracture formation due to drying is a common process in a range of systems, from mud cracks to thin polymeric films. Design and control of the fracturing process can be used as a tool for directing the fractures into predefined paths, leading to patterning and controlled fragmentation. In this work, we report the spontaneous periodic fragmentation of polymeric microfibers upon drying. The microfibers are fabricated via electrospinning of amphiphilic triblock copolymers over a glass substrate, and throughout their drying, highly periodic and sharp transverse cracking occurs along the fiber, resulting in the production of anisotropic microparticles (MPs) with a remarkably narrow size distribution. The average length of the MPs depends on the fiber's diameter; hence, by tuning the diameter of the fibers, size control over the MPs is achieved. X-ray scattering measurements reveal the formation of a lamellar arrangement of the copolymers along the fiber, providing a molecular insight into the formation of sharp transverse fractures. Adjusting the lipophilicity of the two terminal hydrophobic dendritic blocks of the triblock copolymers allows tuning the solubility of the obtained MPs in water and the release rate of hydrophobic cargo, opening a new route for the fabrication of anisotropic MPs for controlled release applications.

Shape-morphing networks of mesoscale filaments are a common hierarchical feature in biology and hold significant potential for a range of technological applications, from micro-muscles to shape-morphing optical devices. Here, we demonstrate both experimentally and computationally that the shape-morphing of highly-ordered 2D networks constructed of thermoresponsive mesoscale polymeric fibers strongly depends on the physical attributes of the single fiber, in particular on its diameter, as well as on the network's density. We show that based on these parameters, such fiber-networks exhibit one of two thermally driven morphing behaviors: (i) the fibers stay straight, and the network preserves its ordered morphology, exhibiting a bulk-like behavior; or (ii) the fibers buckle and the network becomes messy and highly disordered. Notably, in both cases, the networks display memory and regain their original ordered morphology upon shrinking. This hierarchical principle, demonstrated here on a range of networks, offers a new way for controlling the shape morphing of materials with mesoscale resolutions and elucidates that minute changes in the mesoscale structural attributes can translate to a dramatic change in the morphing behaviors at the macroscale.

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.

The vast majority of processes within the cell are carried out by proteins working in conjunction. The Yeast Two-Hybrid (Y2H) methodology allows the detection of physical interactions between any two interacting proteins. Here, we describe a novel systematic genetic methodology, "Reverse Yeast Two-Hybrid Array" (RYTHA), that allows the identification of proteins required for modulating the physical interaction between two given proteins. Our assay starts with a yeast strain in which the physical interaction of interest can be detected by growth on media lacking histidine, in the context of the Y2H methodology. By combining the synthetic genetic array technology, we can systematically screen mutant libraries of the yeast Saccharomyces cerevisiae to identify trans-acting mutations that disrupt the physical interaction of interest. We apply this novel method in a screen for mutants that disrupt the interaction between the N-terminus of Elg1 and the Slx5 protein. Elg1 is part of an alternative replication factor C-like complex that unloads PCNA during DNA replication and repair. Slx5 forms, together with Slx8, a SUMO-targeted ubiquitin ligase (STUbL) believed to send proteins to degradation. Our results show that the interaction requires both the STUbL activity and the PCNA unloading by Elg1, and identify topoisomerase I DNA-protein cross-links as a major factor in separating the two activities. Thus, we demonstrate that RYTHA can be applied to gain insights about particular pathways in yeast, by uncovering the connection between the proteasomal ubiquitin-dependent degradation pathway, DNA replication, and repair machinery, which can be separated by the topoisomerase-mediated cross-links to DNA.