Development of an inexpensive tensiometer for surface tension and contact angle measurements

In this paper we propose a low cost tensiometer that is easily reproducible with the requirement of minimal components and basic technical skills. It mainly uses a low cost Arduino microcontroller and a stepper motor to dispense the liquid. The calibration of the tensiometer was performed using the gravimetric method in order to test its accuracy and reliability. The tensiometer was mounted vertically in order to obtain a uniform shape of the droplet emerged from the tip of a blunt needle fitted at plastic (or glass) syringe which is suspended vertically under gravity. The droplet images were captured with CCD camera and analyzed in the image analysis software in order to calculate the drop shape factor which helps to evaluate the surface tension of the liquid using pendent drop method. The results were achieved within the range of 0.5-1 mN m
^-1
of literature values. Furthermore the sessile droplet method was used for measuring the water contact angle with the solid surface. The images were processed in the image analyzer software in order to measure the contact angle. It reveals that our laboratory made low cost tensiometer enable to measure the wetting properties and surface tension accurately. The accuracy of the instrument is found to be within the range of 1.0 percent in the determination of the surface tension of water.