Assistant Professor Youngstown State University Boardman, Ohio, United States
Introduction: Microfluidic flow cells play an active role in various fields, including analytical chemistry, biotechnology, and medical diagnostics[1]. While microfluidic devices are commonly fabricated via soft-lithography, photolithography, or mold-injection, 3D printing has emerged as an effective alternative[2-4]. Advantages of 3D printing for flow cell construction include: high feature resolution, the capability of creating intricate and complex geometries, a range of material properties, rapid prototyping, and the ability to print multiple flow cells at once. However, industrial laser-based printers suffer from prohibitive high costs and longer print times[4, 5]. Meanwhile, consumer-grade printers and materials have had minimal scientific application and testing. In this study, we propose to apply low cost consumer grade 3D printers and materials to microfluidic flow cell production. The resultant cells will be tested for feature resolution, device and material strength, flow rate, and optical performance. Program success would facilitate a rapid, inexpensive, and highly customizable method for in-house microfluidic device construction.
Materials and
Methods: We are using a consumer grade 3D printer and clear resin, along with cleaning tanks and a curing station for our prints. Tests were conducted using flow cells with channel width ranging from 1mm to 0.2mm in 0.1mm increments, figure 1A. To find the optimum way to print Microfluidic flow cells, we have run a series of tests with different print settings such as supports, exposure time, and print orientation. We have printed horizontally, vertically, and at a 45° angle. Exposure times of 2, 2.5, 3, 3.5, and 4 seconds were tested to determine which achieved the highest resolution. Additionally, we tried multiple different support settings to find which works best. To measure the clarity of the resin, we ran tests with channels of different depths descending from 0.5 to 10mm. Finally, to test the channels for maximum pressure, we hooked them up to a peristaltic pump using pressures from 10 to 450ml/min.
Results, Conclusions, and Discussions: Results and Discussions: We have found that chips printed vertically have the best channels. These prints must be printed on supports, or resin gets trapped inside due to suction force. To prevent print failure, we found that heavy supports work best. That said, the supports trap resin resulting in deformations curing to the print's bottom. Similarly, we have not achieved horizontal channel less than 1mm wide and hypothesize that this is due to UV light transmitting through and curing resin trapped in the channel, figure 1B. Exposure tests have shown mixed results, as a lower exposure time (2, 2.5 and 3 seconds) grants smaller channel size, but also a lower likelihood of a successful print due to underexposure. At higher exposure times (3, 3.5, and 4 seconds), the minimum channel size is larger by 0.1mm, but the prints have a lower likelihood of failure. Prints with lower exposure time can have channels printing down to 200μm in diameter, while prints with higher exposure times consistently print down to 300μm and no smaller. As for the print clarity, the channel gets blurrier as they get deeper. However, when given a topcoat of clear resin after being printed, the shallow channels and deep channels are nearly indistinguishable to the eye, figure 1C. The channels were fully capable of taking on the water pressure at all levels.
Conclusions: While our work shows that SLA printing microfluidic flow cells is possible, it is apparent that there are limitations to this method. Without the right print settings, the prints can be prone to failure. It is also very difficult to produce a channel less than 300μm. For basic purposes, SLA printers can create many microfluidic flow cells. While this does not replace the traditional method of making flow cells, it does offer rapid prototyping of basic microfluidic flow cells and the potential of creating complex geometry in one step.
Acknowledgements (Optional):
References: [1] Niculescu, A.G et al, Int J Mol Sci, 22, 4 (2021). [2] Tiwari, S.K. et al, Sci Rep, 10, 1 (2020). [3] Nielsen, A.V. et al, Annu Rev Anal Chem, 13, 1 (2020). [4] Qiu, J. et al, Materials, 16, 6984 (2023). [5] Gale, B. et al, Inventions, 3, 3 (2018).
