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The measured force during a puncture test is found to increase when the needle tip is near to the vial walls. An experimental method for quantifying this increase in stiffness is developed. 

High-throughput microrheology and simple viscosity modeling can be used to continuously monitor the kinetic evolution of polymer molecular weight during controlled polymerizations. 

Abstract Shear‐recoverable hydrogels based on block copolypeptides with rapid self‐recovery hold potential in extrudable and injectable 3D‐printing applications. In this work, a series of 3‐arm star‐shaped block copolypeptides composed of an inner hydrophilic poly(l‐glutamate) domain and an outer β‐sheet forming domain is synthesized with varying side chains and block lengths. By changing the β‐sheet forming domains, hydrogels with diverse microstructures and mechanical properties are prepared and structure–function relationships are determined using scattering and rheological techniques. Differences in the properties of these materials are amplified during direct‐ink writing with a strong correlation observed between printability and material chemistry. Significantly, it is observed that non‐canonical β‐sheet blocks based on phenyl glycine form more stable networks with superior mechanical properties and writability compared to widely used natural amino acid counterparts. The versatile design available through block copolypeptide materials provides a robust platform to access tunable material properties based solely on molecular design. These systems can be exploited in extrusion‐based applications such as 3D‐printing without the need for additives. 

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. 

Materials that utilize heterogeneous microstructures to control macroscopic mechanical response are ubiquitous in nature. Yet, translating nature's lessons to create synthetic soft solids has remained challenging. This is largely due to the limited synthetic routes available for creating soft composites, particularly with submicron features, as well as uncertainty surrounding the role of such a microstructured secondary phase in determining material behavior. This work leverages recent advances in the development of photocrosslinkable thermogelling nanoemulsions to produce composite hydrogels with a secondary phase assembled at well controlled length scales ranging from tens of nm to tens of μm. Through analysis of the mechanical response of these fluid-filled composite hydrogels, it is found that the size scale of the secondary phase has a profound impact on the strength when at or above the elastofracture length. Moreover, this work shows that mechanical integrity of fluid–filled soft solids can be sensitive to the size scale of the secondary phase.