Xue Fan, Lee Ulri N, Voldman Joel
Massachusetts Institute of Technology, Cambridge, MA, USA.
Microsyst Nanoeng. 2025 May 29;11(1):113. doi: 10.1038/s41378-025-00968-6.
Fluid flow is a ubiquitous aspect of microfluidic systems. Gravity-driven flow is one microfluidic flow initiation and maintenance mechanism that is appealing because it is simple, requires no external power source, and is easy to use. However, the driving forces created by hydraulic head differences gradually decrease during operation, resulting in decreasing flow rates that are undesirable in many microfluidic applications such as perfusion culture, droplet microfluidics, etc. Existing methods to maintain a constant gravity-driven flow either require additional control equipment, involve complex fabrication or operation, are incompatible with miniaturization, or introduce interfaces that lack robustness. Here we tackled those problems by introducing a 3D-printed compact hydraulic head auto-regulating module that automatically maintains a constant fluid level at the microfluidic inlet port without human intervention. Our module successfully maintained a constant hydraulic head for more than 24 h, with the operation time solely limited by the reservoir capacity. A comparison with the conventional gravity-driven flow demonstrated our device's capability to produce a more stable flow over the perfusion period. Overall, our module creates a simple, robust solution to produce a stable flow rate in gravity-driven flow systems. The compactness of the design allows easy parallelization and compatibility with high-throughput applications, and the biocompatibility of the materials enables the device's use with life science applications.
流体流动是微流控系统中普遍存在的一个方面。重力驱动流是一种微流控流动启动和维持机制，它很有吸引力，因为它简单，不需要外部电源，且易于使用。然而，在运行过程中，由液压头差异产生的驱动力会逐渐减小，导致流速降低，这在许多微流控应用中是不可取的，如灌注培养、液滴微流控等。现有的维持恒定重力驱动流的方法要么需要额外的控制设备，涉及复杂的制造或操作，与小型化不兼容，要么引入缺乏稳健性的接口。在这里，我们通过引入一个3D打印的紧凑型液压头自动调节模块来解决这些问题，该模块无需人工干预就能自动维持微流控入口处的恒定液位。我们的模块成功地维持了超过24小时的恒定液压头，运行时间仅受储液器容量的限制。与传统重力驱动流的比较表明，我们的装置在灌注期间能够产生更稳定的流。总体而言，我们的模块为在重力驱动流系统中产生稳定流速创造了一个简单、稳健的解决方案。设计的紧凑性便于轻松并行化并与高通量应用兼容，材料的生物相容性使该装置能够用于生命科学应用。
