Multicrystalline Informatics Applied to Multicrystalline Silicon for Unraveling the Microscopic Root Cause of Dislocation Generation.

A comprehensive analysis of optical and photoluminescence images obtained from practical multicrystalline silicon wafers is conducted, utilizing various machine learning models for dislocation cluster region extraction, grain segmentation, and crystal orientation prediction. As a result, a realistic 3D model that includes the generation point of dislocation clusters is built. Finite element stress analysis on the 3D model coupled with crystal growth simulation reveals inhomogeneous and complex stress distribution and that dislocation clusters are frequently formed along the slip plane with the highest shear stress among twelve equivalents, concentrated along bending grain boundaries (GBs). Multiscale analysis of the extracted GBs near the generation point of dislocation clusters combined with ab initio calculations has shown that the dislocation generation due to the concentration of shear stress is caused by the nanofacet formation associated with GB bending. This mechanism cannot be captured by the Haasen-Alexander-Sumino model. Thus, this research method reveals the existence of a dislocation generation mechanism unique to the multicrystalline structure. Multicrystalline informatics linking experimental, theoretical, computational, and data science on multicrystalline materials at multiple scales is expected to contribute to the advancement of materials science by unraveling complex phenomena in various multicrystalline materials.

Preparation of stripe-patterned heterogeneous hydrogel sheets using microfluidic devices for high-density coculture of hepatocytes and fibroblasts.

Here we demonstrate the production of stripe-patterned heterogeneous hydrogel sheets for the high-density 3D coculture of multiple cell types, by using microchannel-combined micronozzle devices. The prepared hydrogel sheet, composed of multiple regions with varying physical stiffness, regulates the direction of proliferation of encapsulated cells and enables the formation of arrays of rod-like heterotypic organoids inside the hydrogel matrix. We successfully prepared stripe-patterned hydrogel sheets with a uniform thickness of ~100 µm and a width of several millimeters. Hepatoma cells (HepG2) and fibroblasts (Swiss 3T3) were embedded inside the hydrogel matrix and cocultured, to form heterotypic micro-organoids mimicking in vivo hepatic cord structures. The upregulation of hepatic functions by the 3D coculture was confirmed by analyzing liver-specific functions. The presented heterogeneous hydrogel sheet could be useful, as it provides relatively large, but precisely-controlled, 3-dimensional microenvironments for the high-density coculture of multiple types of cells.