A frugal automated contact angle analyser for low-cost surface wettability characterization

Abstract Contact angle measurement is a fundamental technique for evaluating surface wettability in materials science, biomedical engineering and coating technologies. However, the high cost of commercial contact angle analysers limits access to surface characterization, particularly in resource-limited laboratories. This study presents a low-cost automated contact angle analyser developed using frugal engineering principles and open-source hardware. The system integrates Arduino-based control, NEMA 17 stepper-motor actuation, automated microdroplet dispensing, smartphone-based optical imaging and a 3D-printed polylactic acid (PLA) framework. A calibrated 330-step dispensing cycle generated reproducible 5 μl water droplets, with fixed optical alignment minimized operator variability. Wettability measurements were performed on polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC) and aluminium substrates and analysed using ImageJ. Mean contact angles were 108.5° for PTFE, 73.9° for PVC and 85.8° for aluminium, closely matching published literature values. One-way analysis of variance (ANOVA) demonstrated significant differences between substrates (p < 0.001), with measurement variability of ±2.3° indicated good repeatability. The total fabrication cost was £114.26, representing approximately 99% cost reduction compared with commercial instruments. The proposed platform demonstrates that automated, reproducible surface wettability characterization can be achieved using low-cost, open-source instrumentation, providing an accessible solution for research, education and engineering laboratories while broadening access to advanced materials characterization.