Microfluidic devices have a long-standing reputation for providing advantages such as high portability, low cost, and low sample volume relative to other analytical devices. Microfluidic devices can be applied to make viscometers. These microfluidic viscometers bring advantages over commercial viscometers such as reducing the cost and sample volumes. We developed a wax-printed microfluidic viscometer on flexible plastic that is cheaper to produce and requires a sample fluid volume as small as 0.5 µL. Fabrication methods such as screen printing or inkjet printing have been used to develop microfluidic viscometers and have shown promising results along with having the aforementioned benefits over commercial viscometers, but wax printing may be a superior method because it requires fewer steps to produce a viable device. In order to fabricate this viscometer, a microfluidic channel is designed on Inkscape and printed using a ColorQube 8880 wax printer on polyethylene terephthalate (PET) plastic substrate. Another polyethylene top-layer substrate is placed onto the printed channel and the channel is subsequently sandwiched between two glass slides and clamped for stability. A digital microscope is used to record the device while sample fluid is run through the channel. This recording is then analyzed using Media Player Classic, a video analyzing software. Viscosity is determined by fluid flow velocity in the channel, with a higher flow velocity correlating to lower viscosity. To measure flow velocity, a simple v = d/t formula is used. In order to create a standard curve, viscosity standards were made using water-glycerol mixtures. This study shows that this wax-printed microfluidic device can differentiate between the flow velocity of viscosity standards ranging from 1.00 cP to 3.00 cP. This microfluidic viscometer design has potential to significantly lower the cost of commercial viscometers in the future, thus increasing the availability of viscosity measurement for low volume samples.

Development of economical, low cost wax-on-plastic microfluidic viscometer

ACS Spring 2022

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