Optical and structural properties of starch films formed on drying droplets of gelatinized starch solutions

TL;DR

This study investigates the optical and structural characteristics of starch films formed on drying droplets, revealing their shape, crystallinity, optical anisotropy, and micro-structure through experimental analysis.

Contribution

It provides new insights into the formation, shape, and optical properties of starch films from drying droplets, including birefringence variation and micro-structural analysis.

Findings

Films are circular with an M-shaped height profile.

They are semi-crystalline and transparent.

Optical properties vary radially with birefringence.

Abstract

We report the optical and structural properties of starch films formed on drying droplets of starch solutions on a flat substrate. The starch films formed after drying are circular in shape and have an azimuthally symmetric "M-shaped" height profile along their diameter. These films are found to be semi-crystalline in nature and transparent in visible light. Our experimental results show that these films are optically uniaxial at their center but biaxial away from the center. The variation of birefringence along the radial direction is studied for the films formed after drying droplets with different volumes and starch concentrations. The cryo-SEM studies on the drying droplets and the films reveal the micro-structures and the possible origin of birefringence of these films.