Droplet Microfluidics for Chip-Based Diagnostics

Abstract

Droplet microfluidics (DMF) is a fluidic handling technology that enables precision control over dispensing and subsequent manipulation of droplets in the volume range of microliters to picoliters, on a micro-fabricated device. There are several different droplet actuation methods, all of which can generate external stimuli, to either actively or passively control the shape and positioning of fluidic droplets over patterned substrates. In this review article, we focus on the operation and utility of electro-actuation-based DMF devices, which utilize one or more micro-/nano-patterned substrates to facilitate electric field-based handling of chemical and/or biological samples. The underlying theory of DMF actuations, device fabrication methods and integration of optical and opto-electronic detectors is discussed in this review. Example applications of such electro-actuation-based DMF devices have also been included, illustrating the various actuation methods and their utility in conducting chip-based laboratory and clinical diagnostic assays.

Recent Advances in Applications of Droplet Microfluidics

“…The performance of droplet microfluidics is suitable for miniaturized diagnosis platforms [58,63,66]. Droplet microfluidics can perform clinical laboratory tests by a part of reagents and in a short period.…”

“…Droplet microfluidics establishes new frontiers and provides promising and powerful platforms for precise production of novel functional materials as drug delivery vehicles and drug molecules [8,16,58,62,63]. In the medical field, drugs can be supported to these fine particles, forming a type of drug delivery system for releasing drugs.…”

“…According to mature detection of nucleic acids in droplet microfluidics, a similar analysis can be applied to many other assay systems [68]. In addition, Kaler et al reviewed electroactuation-based droplet microfluidics and its clinical diagnostic assays in nucleic acid amplification and real-time detection, immunoassays, and protein analysis [63]. Several recent applications of droplet microfluidics involving diagnostic chips are summarized in Table 4.…”

Droplet Merging on a Lab-on-a-Chip Platform by Uniform Magnetic Fields

“…Droplet manipulation on a LoC platform has been used for the synthesis of novel materials6 relevant to biosensing7, three-dimensional (3D) cell culture8, photonic crystals9, Janus structures10, anisotropic particles11, functional polymeric structures121314, controlled encapsulation for drug delivery15 and multidimensional optical barcoding16. Specifically, droplet merging and mixing on LoC platform has been used for a broad range of biomedical applications17 such as bioassays1819, biomaterials20, single cell analysis21, cell sorting2223, population transcriptomics24, disease detection25, and diagnostics26. Merging and mixing of droplets on a LoC platform can also lead to miniaturized volume conditions (nl to pl), reduced operation time and several fold increase in screening of chemical reactions27, which opens a new domain of DMF chemistry2829, drug discovery applications303132, high-throughput molecular genetics33, interfacial studies34 and ‘on water reaction’35.…”

Droplet Manipulations in Two Phase Flow Microfluidics

“…There are short overviews on available techniques for droplet generation [8][9][10], methods for single cell encapsulation [11], passive microfluidic techniques [12], manipulations using electrowetting [13,14], as well as on the fundamental challenges involved [15], on the (need for) integration of biology, chemistry and physics in biological assays [16][17][18], on the choice of optimal surfactants [19], and even comprehensive review articles [20][21][22] and books [23] covering the entire field of droplet based microfluidics. The theoretical fluid physics aspects behind microfluidics have also been covered [24].…”