Department of Mechanical Engineering, Iowa State University of Science and Technology, 528 Bissell Rd, Ames, IA 50010, USA.
Nanoscale Horiz. 2021 Jan 5;6(1):24-32. doi: 10.1039/d0nh00376j.
Open microfluidics have emerged as a low-cost, pumpless alternative strategy to conventional microfluidics for delivery of fluid for a wide variety of applications including rapid biochemical analysis and medical diagnosis. However, creating open microfluidics by tuning the wettability of surfaces typically requires sophisticated cleanroom processes that are unamenable to scalable manufacturing. Herein, we present a simple approach to develop open microfluidic platforms by manipulating the surface wettability of spin-coated graphene ink films on flexible polyethylene terephthalate via laser-controlled patterning. Wedge-shaped hydrophilic tracks surrounded by superhydrophobic walls are created within the graphene films by scribing micron-sized grooves into the graphene with a CO2 laser. This scribing process is used to make superhydrophobic walls (water contact angle ∼160°) that delineate hydrophilic tracks (created through an oxygen plasma pretreatment) on the graphene for fluid transport. These all-graphene open microfluidic tracks are capable of transporting liquid droplets with a velocity of 20 mm s-1 on a level surface and uphill at elevation angles of 7° as well as transporting fluid in bifurcating cross and tree branches. The all-graphene open microfluidic manufacturing technique is rapid and amenable to scalable manufacturing, and consequently offers an alternative pumpless strategy to conventional microfluidics and creates possibilities for diverse applications in fluid transport.
开式微流控技术作为一种低成本、无泵替代策略，已经在各种应用中崭露头角，包括快速生化分析和医疗诊断等领域，用于输送流体。然而，通过调整表面润湿性来创建开式微流控通常需要复杂的洁净室工艺，而这些工艺不适用于可扩展制造。在此，我们通过激光控制图案化，对涂覆在柔性聚对苯二甲酸乙二醇酯上的旋涂石墨烯油墨薄膜的表面润湿性进行操控，提出了一种简单的方法来开发开式微流控平台。通过二氧化碳激光在石墨烯上刻入微米级的沟槽，在石墨烯薄膜内制造出楔形亲水轨道，轨道周围是超疏水壁。通过氧等离子体预处理在石墨烯上制造亲水轨道（水接触角约 160°），用于流体输送，从而利用该刻蚀工艺来制造超疏水壁。这些全石墨烯开式微流道能够在水平表面上以 20mm/s 的速度输送液滴，并能在 7°的仰角处向上输送液体，还能在交叉和树状分支中输送流体。全石墨烯开式微流控制造技术快速且适用于可扩展制造，因此为传统微流控提供了一种无泵替代策略，并为流体输送的各种应用创造了可能性。
