Designing and 3D Printing an Improved Method of Measuring Contact Angle in the Middle School Classroom

The interaction between water and surfaces is observed in our daily lives and is used in laboratories to study materials properties, such as interfacial tension. Making the connection between fundamental scientific phenomena and everyday observations is a powerful method of highlighting the importance and relevance of science to the K-12 population. Typically, expensive equipment, such as dedicated contact angle goniometers, is used in laboratories to observe how water interacts with materials. Obtaining such laboratory-grade equipment for the K-12 classroom is not only difficult but also unnecessary. Thus, we present an affordable 3D printed setup for the reliable measurement of the contact angle of water on a variety of natural and synthetic surfaces, using smart devices (e.g., cell phone, tablet) as the imaging basis. This setup enables proper backlighting, a stable camera holder for quality images, and a flat surface with an easily adjustable platform to hold the sample. Compared to simply holding the smart device by hand, the 3D printed method provided better quality images and an improved data acquisition experience when measuring the contact angle. Use in a middle school setting has shown that this 3D printed method is successful for teaching about water/surface interactions on both hydrophilic and hydrophobic surfaces. This method can easily be adapted to suit learning objectives, allowing educators to explore a range of hydrophobic and hydrophilic surfaces of both biological and synthetic origin.