SSEF Merit Award

We need to wash our hands, dishes, clothes, etc. Hence, it is important to analyse the strength of hand soap and dishwashing liquid. For this purpose, we used Precision Ellipsometry (PREL), a novel optical technique that utilises polarised light to measure the thickness of thin films. The thickness of a film can be measured to a high precision in real time by measuring the change in polarisation of light and the phase shift between in plane and normal components of the reflected light. For PREL analysis, we immobilised Ovalbumin (OVA) on the silicon substrate. Then, we analysed the detachment of Ovalbumin (OVA) after addition of detergent by measuring the change in thickness of the layer on the substrate. The experiment was also tested under 2 different conditions, where detergent was added right after attachment of OVA (wet), and detergent was added after the substrate was left to dry for 24 to 48 hours (dry). Results showed that the rate of detachment of OVA was higher in dry conditions than in wet conditions, although the amount of OVA detached was similar. Higher concentrations of detergent were shown to cause a greater rate and amount of detachment of OVA than in lower concentrations. Dishwashing liquid also caused an increased rate and amount of detachment of OVA than hand soap.