A design framework for the fabrication of a low-cost goniometer apparatus for contact angle and surface tension measurements

Abstract

In recent years, an increasing number of reported studies and technological applications have relied on controlling the wetting behavior at the solid–liquid interface. In order to study wetting behavior, the contact angle based on the sessile droplet method and the surface tension using the pendant droplet method are the most widely used metrics, which are conventionally obtained using a goniometer. However, commercial goniometers are usually expensive. making them inaccessible to those under budget constraints. Focussing on how to design and fabricate goniometer setups in-house, we establish here a design framework based on the essential requirements and experimentally validate the use of the fabricated goniometers for the measurement of contact angle and surface tension. Specifically, a functionality-centric approach has been adopted, instead of component-centric, so that goniometers can be made with available components and low-cost substitutes that are capable of serving similar functionalities. Based on these requirements, we present two low-cost goniometer designs fabricated in-house with locally and easily available components. The construction materials and components for the two in-house built goniometers are different, while they serve similar functionalities which were identified as a part of the design framework. The two goniometers fabricated in-house are extremely low cost, with the overall cost of both the goniometers being less than 160 USD. The performance of the goniometers was successfully validated by evaluating and comparing the contact angle and surface tension values with those of a commercial system. Such low-cost goniometer prototypes can serve the technological needs of research labs as well as in imparting practical learning about surface science in classroom settings.