Design and development of a microfluidic droplet generator with vision sensing for lab-on-a-chip devices

• Published in: Sensors and actuators. A. Physical. 2021-12, Vol.332, p.113047, Article 113047
• Main Authors: Hettiarachchi, Samith, Melroy, Gehan, Mudugamuwa, Amith, Sampath, Peshan, Premachandra, Charith, Amarasinghe, Ranjith, Dau, Van
• Format: Article
• Language: English
• Subjects: Active droplet generator; Algorithms; Computer simulation; Devices; Digital imaging; Droplets; Experimentation; Flow velocity; Flow-focusing; Fluid dynamics; Generators; Heat transfer; Image processing; Lab-on-a-chip; Mathematical models; Microfluidics; Polymethyl methacrylate; Simulation; Vision sensing
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2021.113047

•Contraction width of the flow-focusing geometry was optimized.•Layer based fabrication method was used to produce the droplet generator.•Active droplet generation was achieved using two submerge pumps.•Vision sensing was used to determine the diameter of generated droplets. [Display omitted] Lab on a Chip (LOC) devices minimize, integrate, automate, and parallelize laboratory functions such as mixing, separation, and incubation on a single chip. Droplet generation is one key aspect in LOC devices which allows to conduct various chemical and biochemical assays enabling biological cell studies, high throughput drug development, and diagnostic screenings. This paper presents, modelling, simulation, and experimentation of an active droplet generator that is widely used in LOC devices. The model geometry used in this study was based on a flow focusing method of droplet generation. Droplet generation from the numerical simulations was observed within flow rate ratios ranging from 0.2 to 4 using optimised droplet contraction width of the generator model. Subsequently, a prototype droplet generator was designed and developed from Polymethyl Methacrylate (PMMA) material using a layer-based fabrication method. Based on the experimental setup presented here, the calculated ratios of flow rates obtained for different voltage values have shown that the formation of droplets occur between flow rate ratios of 1.04 and 4.74. In addition, morphological parameters of the droplet images extracted from a digital image processing algorithm show that the mean diameter of the droplets decreases with decreasing flow rate ratios.