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Light-responsive liquid crystal elastomer networks (LCNs) have received significant interest due to their potential application in soft robotics and shape-morphing devices. Here, we present a systematic examination of light responsive LCNs prepared using a catalyst-free Diels–Alder cycloaddition and a new azobenzene functionalized monomer for main-chain incorporation. The networks have robust mechanical stiffness that can be reversibly modulated by 1 GPa by turning the UV light on and off. This study highlights the contribution of photothermal softening to reversibly control rheological properties of the newly developed LCNs and demonstrates the ability to tune the modulus on demand. We believe this work will guide future developments of light-responsive LCNs based on the newly developed Diels–Alder cycloaddition. 

The ability of cells to reorganize in response to external stimuli is important in areas ranging from morphogenesis to tissue engineering. While nematic order is common in biological tissues, it typically only extends to small regions of cells interacting via steric repulsion. On isotropic substrates, elongated cells can co-align due to steric effects, forming ordered but randomly oriented finite-size domains. However, we have discovered that flat substrates with nematic order can induce global nematic alignment of dense, spindle-like cells, thereby influencing cell organization and collective motion and driving alignment on the scale of the entire tissue. Remarkably, single cells are not sensitive to the substrate’s anisotropy. Rather, the emergence of global nematic order is a collective phenomenon that requires both steric effects and molecular-scale anisotropy of the substrate. To quantify the rich set of behaviours afforded by this system, we analyse velocity, positional and orientational correlations for several thousand cells over days. The establishment of global order is facilitated by enhanced cell division along the substrate’s nematic axis, and associated extensile stresses that restructure the cells’ actomyosin networks. Our work provides a new understanding of the dynamics of cellular remodelling and organization among weakly interacting cells.

 

Light‐responsive liquid crystal elastomers (LCEs) are stimuli‐responsive materials that facilitate the conversion of light energy into a mechanical response. In this work, a novel polysiloxane‐based LCE with donor–acceptor Stenhouse adduct (DASA) side‐chains is synthesized using a late‐stage functionalization strategy. It is demonstrated that this approach does not compromise the molecular alignment observed in the traditional Finkelmann method. This easy, single‐batch process provides a robust platform to access well‐aligned, light‐responsive LCE films with thickness ranging from 400 µm to a 14‐layer stack that is 5 mm thick. Upon irradiation with low‐intensity broadband visible light (100–200 mW cm⁻²), these systems undergo 2D planar actuation and complete bleaching. Conversely, exposure to higher‐intensity visible light induces bending followed by contraction (300 mW cm⁻²). These processes are repeatable over several cycles. Finally, it is demonstrated how light intensity and the resulting heat generation influences the photothermal stationary state equilibrium of DASA, thereby controlling its photoresponsive properties. This work establishes the groundwork for advancement of LCE‐based actuators beyond thin film and UV‐light reliant systems.

 

Aligned liquid crystal polymers are materials of interest for electronic, optic, biological and soft robotic applications. The manufacturing and processing of these materials have been widely explored with mechanical alignment establishing itself as a preferred method due to its ease of use and widespread applicability. However, the fundamental chemistry behind the required two‐step polymerization for mechanical alignment has limitations in both fabrication and substrate compatibility. In this work we introduce a new protection‐deprotection approach utilizing a two‐stage Diels–Alder cyclopentadiene‐maleimide step‐growth polymerization to enable mild yet efficient, fast, controlled, reproducible and user‐friendly polymerizations, broadening the scope of liquid crystal systems. Thorough characterization of the films by DSC, DMA, POM and WAXD show the successful synthesis of a uniaxially aligned liquid crystal network with thermomechanical actuation abilities.

 

Aligned liquid crystal polymers are materials of interest for electronic, optic, biological and soft robotic applications. The manufacturing and processing of these materials have been widely explored with mechanical alignment establishing itself as a preferred method due to its ease of use and widespread applicability. However, the fundamental chemistry behind the required two‐step polymerization for mechanical alignment has limitations in both fabrication and substrate compatibility. In this work we introduce a new protection‐deprotection approach utilizing a two‐stage Diels–Alder cyclopentadiene‐maleimide step‐growth polymerization to enable mild yet efficient, fast, controlled, reproducible and user‐friendly polymerizations, broadening the scope of liquid crystal systems. Thorough characterization of the films by DSC, DMA, POM and WAXD show the successful synthesis of a uniaxially aligned liquid crystal network with thermomechanical actuation abilities.