A Polymer Microdevice for Tensiometry of Insoluble Components

A semi-flexible SU-8 polymer microdevice was designed to deflect in response to a change in surface tension at an air-water interface. The suspended microtensiometer encloses a clean water-air interface, while externally the device is surrounded by an interface containing an insoluble component. The difference in surface tension between the inside and outside of the device, called the surface pressure, causes the device to deflect. Finite element simulations were performed to predict device behavior prior to fabrication. Finished devices were tested in a Langmuir trough during multiple compression and expansion cycles, using a platinum Wilhelmy plate for an independent surface pressure measurement. A resolution of 0.16 mN/m was achieved.