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Mesenchymal–epithelial transition (MET) is essential for tissue and organ development and is thought to contribute to cancer by enabling the establishment of metastatic lesions. Despite its importance in both health and disease, there is a lack of in vitro platforms to study MET and little is known about the regulation of MET by mechanical cues. Here, hyaluronic acid‐based hydrogels with dynamic and tunable stiffnesses mimicking that of normal and tumorigenic mammary tissue are synthesized. The platform is then utilized to examine the response of mammary epithelial cells and breast cancer cells to dynamic modulation of matrix stiffness. Gradual softening of the hydrogels reduces proliferation and increases apoptosis of breast cancer cells. Moreover, breast cancer cells exhibit temporal changes in cell morphology, cytoskeletal organization, and gene expression that are consistent with mesenchymal–epithelial plasticity as the stiffness of the matrix is reduced. A reduction in matrix stiffness attenuates the expression of integrin‐linked kinase, and inhibition of integrin‐linked kinase impacts proliferation, apoptosis, and gene expression in cells cultured on stiff and dynamic hydrogels. Overall, these findings reveal intermediate epithelial/mesenchymal states as cells move along a matrix stiffness‐mediated MET trajectory and suggest an important role for matrix mechanics in regulating mesenchymal–epithelial plasticity.

All‐solid‐state batteries have the potential for enhanced safety and capacity over conventional lithium ion batteries, and are anticipated to dominate the energy storage industry. As such, strategies to enable recycling of the individual components are crucial to minimize waste and prevent health and environmental harm. Here, we use cold sintering to reprocess solid‐state composite electrolytes, specifically Mg and Sr doped Li₇La₃Zr₂O₁₂with polypropylene carbonate (PPC) and lithium perchlorate (LLZO−PPC−LiClO₄). The low sintering temperature allows co‐sintering of ceramics, polymers and lithium salts, leading to re‐densification of the composite structures with reprocessing. Reprocessed LLZO−PPC−LiClO₄exhibits densified microstructures with ionic conductivities exceeding 10⁻⁴ S/cm at room temperature after 5 recycling cycles. All‐solid‐state lithium batteries fabricated with reprocessed electrolytes exhibit a high discharge capacity of 168 mA h g⁻¹at 0.1 C, and retention of performance at 0.2 C for over 100 cycles. Life cycle assessment (LCA) suggests that recycled electrolytes outperforms the pristine electrolyte process in all environmental impact categories, highlighting cold sintering as a promising technology for recycling electrolytes.

The glass transition temperature (T_g) is a key property that dictates the applicability of conjugated polymers. TheT_gdemarks the transition into a brittle glassy state, making its accurate prediction for conjugated polymers crucial for the design of soft, stretchable, or flexible electronics. Here we show that a single adjustable parameter can be used to build a relationship between theT_gand the molecular structure of 32 semiflexible (mostly conjugated) polymers that differ drastically in aromatic backbone and alkyl side chain chemistry. An effective mobility value,ζ, is calculated using an assigned atomic mobility value within each repeat unit. The only adjustable parameter in the calculation ofζis the ratio of mobility between conjugated and non-conjugated atoms. We show thatζcorrelates strongly to theT_g, and that this simple method predicts theT_gwith a root-mean-square error of 13 °C for conjugated polymers with alkyl side chains.

Both the mechanical deformability and electronic conductivity of conjugated polymers play important roles in the development of wearable and stretchable electronics. Despite the recent progress and emphasis on achieving highly stretchable and conductive devices, the correlation between the mechanical and conductive properties is poorly understood and remains mostly empirical. The future of flexible electronics relies on the ability to predict and tune the mechanical and conductive properties such that the molecular design of conjugated polymers can be optimized for various applications. Instead of seeking a direct correlation between mechanical and conductive properties, this Progress Report proposes to examine the common microstructural origin for mechanical performance and charge transport in conjugated polymers. Measurements of microstructural information, such as persistence length, chain entanglement, glass transition, liquid crystalline phase transition, and intercrystalline morphology, are desperately needed in the field of conjugated polymers in order to establish connections with both the mechanical/conductive properties and the chemical structures. Conventional experimental methods in the field of flexible polymer physics, such as linear viscoelastic rheometry, open up new avenues for characterizing these microstructural parameters, thereby providing a path toward predicting and designing the molecular structure of conjugated polymers with desired mechanical and conductive properties.