Lab-on-a-Disk Particle Separation Using a Novel Automated Slab Valve for Two-Step Filtration

Urological symptoms are usually accompanied by several etiologies; therefore, diagnosis is often based on multiple tests, which include imaging and urine analysis, among others. One of the most frequent causes of sharp pain in the population is kidney stones, which usually develop in the renal system. It would be possible to determine the levels of kidney stones appropriately by analyzing the size distribution of substances, such as crystals, in a urine sample. These polyester mesh filters in microfluidic devices represent the state-of-the-art solution in rapid and precise crystal isolation and identification. In the present study, we are presenting a centrifugal microfluidic platform for such an application. The proposed system uses centrifugal force to drive the urine sample through mesh filters of selectable pore sizes. Employing an innovative valving strategy, a backwash step enables the retrograde flow of washing liquid to displace trapped larger particles into a dedicated detection chamber. The introduced backwash process represents the foremost advantage of this microfluidics-based filtration device, facilitating high-resolution trapping of particles of specific sizes. Furthermore, the system boasts user-friendly operation and affordability. Experimental results demonstrate the system’s capability to effectively filter particles larger than 15 µm from heterogeneous samples in under 5 min. Optimization of disc rotational velocity ensures optimal liquid discharge timing and particle retrieval. Subsequently, we apply the system to the filtration of crystals from urine samples. Image processing of specimens within collection chambers underscores the technique’s proficiency in classifying crystals within samples into normal and high-risk categories.