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Dynamic windows based on reversible metal electrodeposition are an attractive way to enhance the energy efficiency of buildings and show great commercial potential. Dynamic windows that rely on liquid electrolytes are at risk of short circuiting when two electrodes contact, especially at larger-scale. Here we developed a poly (vinyl alcohol) (PVA) gel polymer electrolyte (GPE) with 85% transmittance, that is, sufficiently stiff to act as a separator. The GPE is implemented into windows that exhibit comparable electrochemical and optical properties to windows using a liquid electrolyte. Furthermore, the GPE enables the fabrication of windows with dual-working electrodes (WE) and a metal mesh counter electrode in the center without short-circuiting. Our dual-WE PVA GPE window reaches the 0.1% transmittance state in 101 s, more than twice the speed of liquid windows with one working electrode (207 s). Additionally, each side of the dual-WE GPE window can be tinted individually to demonstrate varied optical effects (i.e., more reflective, or more absorptive), providing users and intelligent building systems with greater control over the appearance and performance of the windows in a single device architecture. 

Spatiotemporally coordinated transformations in epithelial curvature are necessary to generate crypt-villus structures during intestinal development. However, the temporal regulation of mechanotransduction pathways that drive crypt morphogenesis remains understudied. Intestinal organoids have proven useful to study crypt morphogenesis in vitro, yet the reliance on static culture scaffolds limits the ability to assess the temporal effects of changing curvature. Here, a photoinduced hydrogel cross-link exchange reaction is used to spatiotemporally alter epithelial curvature and study how dynamic changes in curvature influence mechanotransduction pathways to instruct crypt morphogenesis. Photopatterned curvature increased membrane tension and depolarization, which was required for subsequent nuclear localization of yes-associated protein 1 (YAP) observed 24 hours following curvature change. Curvature-directed crypt morphogenesis only occurred following a delay in the induction of differentiation that coincided with the delay in spatially restricted YAP localization, indicating that dynamic changes in curvature initiate epithelial curvature–dependent mechanotransduction pathways that temporally regulate crypt morphogenesis. 

Stiffness and forces are two fundamental quantities essential to living cells and tissues. However, it has been a challenge to quantify both 3D traction forces and stiffness (or modulus) using the same probe in vivo. Here, we describe an approach that overcomes this challenge by creating a magnetic microrobot probe with controllable functionality. Biocompatible ferromagnetic cobalt-platinum microcrosses were fabricated, and each microcross (about 30 micrometers) was trapped inside an arginine–glycine–aspartic acid–conjugated stiff poly(ethylene glycol) (PEG) round microgel (about 50 micrometers) using a microfluidic device. The stiff magnetic microrobot was seeded inside a cell colony and acted as a stiffness probe by rigidly rotating in response to an oscillatory magnetic field. Then, brief episodes of ultraviolet light exposure were applied to dynamically photodegrade and soften the fluorescent nanoparticle–embedded PEG microgel, whose deformation and 3D traction forces were quantified. Using the microrobot probe, we show that malignant tumor–repopulating cell colonies altered their modulus but not traction forces in response to different 3D substrate elasticities. Stiffness and 3D traction forces were measured, and both normal and shear traction force oscillations were observed in zebrafish embryos from blastula to gastrula. Mouse embryos generated larger tensile and compressive traction force oscillations than shear traction force oscillations during blastocyst. The microrobot probe with controllable functionality via magnetic fields could potentially be useful for studying the mechanoregulation of cells, tissues, and embryos. 

Abstract 3D organoid models have recently seen a boom in popularity, as they can better recapitulate the complexity of multicellular organs compared to other in vitro culture systems. However, organoids are difficult to image because of the limited penetration depth of high‐resolution microscopes and depth‐dependent light attenuation, which can limit the understanding of signal transduction pathways and characterization of intimate cell‐extracellular matrix (ECM) interactions. To overcome these challenges, phototransfer by allyl sulfide exchange‐expansion microscopy (PhASE‐ExM) is developed, enabling optical clearance and super‐resolution imaging of organoids and their ECM in 3D. PhASE‐ExM uses hydrogels prepared via photoinitiated polymerization, which is advantageous as it decouples monomer diffusion into thick organoid cultures from the hydrogel fabrication. Apart from compatibility with organoids cultured in Matrigel, PhASE‐ExM enables 3.25× expansion and super‐resolution imaging of organoids cultured in synthetic poly(ethylene glycol) (PEG) hydrogels crosslinked via allyl‐sulfide groups (PEG‐AlS) through simultaneous photopolymerization and radical‐mediated chain‐transfer reactions that complete in <70 s. Further, PEG‐AlS hydrogels can be in situ softened to promote organoid crypt formation, providing a super‐resolution imaging platform both for pre‐ and post‐differentiated organoids. Overall, PhASE‐ExM is a useful tool to decipher organoid behavior by enabling sub‐micrometer scale, 3D visualization of proteins and signal transduction pathways.