Salt Whisker Growth through Macromolecular Crowding\nMatrix Regulation

The\nstable and controlled substance transportation regulated by\nintricate mechanisms in nature enables the growth of an elaborate\ncrystal structure under diffusion control, exemplified by many biological\nbehaviors such as biomineralization. Crystal growth in oversaturated\nsolutions often faces challenges in controlling the growth direction\nand morphologies, especially within unregulated, simple artificial\nenvironments. In this study, polyampholyte (PA) hydrogels synthesized\nthrough the random copolymerization of cationic and anionic monomers\nwere employed as a matrix for directional salt crystal growth. This\napproach successfully facilitated the large-scale growth of sodium\nchloride salt whiskers (SWs) on the surface of the PA substrate. Real-time\nobservation of the growth process and surface morphology evolution\nof SWs on the PA substrate revealed two distinct SW morphologies,\nsuggesting that multiple mechanisms are involved in their development.\nThe demonstration of growing SWs using a PA gel matrix offers a scalable\nand practical approach for one-dimensional salt crystal synthesis.\nPA, as a representative hydrogel matrix with a tunable charged macromolecular\ncrowding environment, serves as a promising model for investigating\nbiomineralization, encompassing substance transport and crystal growth.