Pattern formation in droplets of starch gels containing NaCl dried on different surfaces

A colloidal gel containing an inorganic salt is a very interesting system. The simple process of drying a small droplet of such a solution on a solid surface produces a fascinatingly rich variety of patterns at different length scales. We create some patterns by this method, with NaCl as the inorganic salt and show that the details of their morphology depend on several factors e.g. (a) the host gel, (b) the proportion of salt and (c) the solid substrate. Besides these, ambient conditions like temperature and humidity also have a role to play. Potato starch and carboxy-methyl cellulose are used to prepare the solvent gel, while the solid surfaces studied as substrate material are glass, polypropylene and two metals – copper and aluminium.