I am using a DCAT 21 precision microelectronic balance with Dr. Jaroslaw Drelich at Michigan Technological University to measure capillary forces between water and hydrocarbons. The hydrocarbon is placed in a concave-up petri dish, which is placed on the balance before a test is started. The DCAT 21 uses a horizontal CCD camera to capture contact angles during a test. Unfortunately, we cannot get contact angles since the petri dish blocks the view CCD camera.

 

The device on this page should work as a "hydrocarbon infinity pool," where liquid fills up the middle section and is spilled to the outside. The angle built into the pool base creates a concave-down hydrocarbon meniscus so that the hydrocarbon stays above the PLA. The device was designed in OpenSCAD and is parametric (source code is available on this page). To use this device, simply fill up the middle with hydrocarbon until the liquid is above the plastic. Then, run a capillary force test as directed by the instrument.

 

Be aware that low-molecular weight hydrocarbons do dissolve small amounts of PLA, so this holder would need to be coated or printed out of a different material to be used in these applications. Let me know if you find a material that works well for you.

 

This design uses approximately 319 cm of 1.75 mm PLA filament. This translates to 9.52 grams of PLA per print. Assuming a cost of $25 per kilogram of PLA, this means one print costs $0.24. There is no known commercial equivalent.