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In a new seed project within the Northwestern University MRSEC, a novel approach for discovering and designing materials is being developed using directed evolution. While directed evolution approaches have been successfully applied in areas such as therapeutics or catalysis, this strategy has not been fully explored in materials science and engineering.

Princeton researchers have demonstrated that acid pre-treatment of NaCrS2 to form a new phase (named HxCrS2) results in significant improvements to the material’s performance as a sodium battery electrode.

Electrohydrodynamic ink jet printing has been used to print  CsPbBr3 nanocrystals into very small features, with spot sizes down to only a few hundred nanometers across. The nanocrystals survive the printing, and even spontaneously self-organize into superlattices.

Susan J. Muller, University of California Berkeley, and Eric S.G. Shaqfeh, Stanford Highlight from Stanford MRSEC 0213618

Electronic  nematicity  is  a  correlated  electronic  state  in  solids  that spontaneously breaks rotational symmetry. This work found that in Fe1+yTe1-xSex,  one  of  the  most  strongly  correlated  iron-based superconductors,   electronic   nematicity   is   closely   linked   to magnetism,   and   its   fluctuations   may   be   responsible   for superconducting pairing.

Researchers at UPenn investigate the fracture behavior of disordered polymer-infiltrated nanoparticle films (PINFs). Here, the extent of polymer confinement in PINFs was tuned over three orders of magnitude NPs of varying size and polymers with varying molecular weight. The results show that brittle, low molecular weight (MW) polymers can significantly toughen NP packings, and this toughening effect becomes less pronounced with increasing NP size. 

Granular hydrogels are jammed assemblies of hydrogel microparticles (i.e., “microgels”) widely explored in biomedical applications due to promising features such as shear-thinning to permit injectability and inherent porosity for cellular interactions. One area where this is particularly promising is in 3D printing. 

Cells and tissues are subjected to external mechanical stresses in the body, including compressive loads, pressure gradients, and shear. This study shows that single cells become harder when compressed and that the parts inside the cells that make them strong (called the cytoskeleton) change when they are compressed. Some cells, like fibroblasts, become harder when subjected to moderate compression. However, this does not happen if a part of the cytoskeleton called vimentin is removed. This is because vimentin networks become harder when compressed or extended. This is explained using a theoretical model to based on the flexibility of vimentin filaments and their surface charge, which resists volume changes of the network under compression.

Liquid crystal elastomers (LCEs) with intrinsic molecular anisotropy can be preprogrammed to morph shapes from 2D to 3D under external stimuli. However, it is difficult to program the positions and orientations of individual building blocks separately and locally as they are chemically linked in the polymer network.

Philadelphia Materials Day is a collaborative effort between the University of Pennsylvania MRSEC and the Materials Science & Engineering Department at Drexel University to promote materials research in the region. The 12th annual Philadelphia Materials Day took place on February 11, 2023 at the Bossone Research Center at Drexel University.