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Recently there has been a more focus on the development of an efficient technique for detection of circulating tumor cells (CTCs), due to their significance in prognosis and therapy of metastatic cancer. However, it remains a challenge because of the low count of CTCs in the blood. Herein, a rapid and high-sensitivity approach for CTCs detection using an integrated microfluidic system, consisting of a deterministic lateral displacement (DLD) isolating structure, an automatic purifying device with CD45-labeled immunomagnetic beads and a capturing platform coated with rat-tail collagen was reported. We observed high capture rate of 90%, purity of about 50% and viability of more than 90% at the high throughput of 1 mL/min by capturing green fluorescent protein (GFP)-positive cells from blood. Further capturing of CTCs from metastatic cancers patients revealed a positive capture rate of 83.3%. Furthermore, our device was compared with CellSearch system via parallel analysis of 30 cancer patients, to find no significant difference between the capture efficiency of both methods. However, our device displayed advantage in terms of time, sample volume and cost for analysis. Thus, our integrated device with sterile environment and convenient use will be a promising platform for CTCs detection with potential clinical application.

Electroosmotic flow is the transport method of choice in microfluidic devices over traditional pressure-driven flow. To date, however, studies on electroosmotic flow have been almost entirely limited to inside microchannels. This work presents the first experimental study of Joule heating effects on electroosmotic fluid entry from the inlet reservoir (i.e., the well that supplies fluids and samples) to the microchannel in a polymer-based microfluidic chip. Electrothermal fluid circulations are observed at the reservoir-microchannel junction, which grow in size and strength with the increasing alternating current to direct current voltage ratio. Moreover, a 2D depth-averaged numerical model is developed to understand the effects of Joule heating on fluid temperature and flow fields in electrokinetic microfluidic chips. This model overcomes the problems encountered in previous unrealistic 2D and costly 3D models, and is able to predict the observed electroosmotic entry flow patterns with a good agreement.

The resistive pulse sensing (RPS) method based on the Coulter principle is a powerful method for particle counting and sizing in electrolyte solutions. With the advancement of micro- and nano-fabrication technologies, microfluidic and nanofluidic resistive pulse sensing technologies and devices have been developed. Due to the unique advantages of microfluidics and nanofluidics, RPS sensors are enabled with more functions with greatly improved sensitivity and throughput and thus have wide applications in fields of biomedical research, clinical diagnosis, and so on. Firstly, this paper reviews some basic theories of particle sizing and counting. Emphasis is then given to the latest development of microfuidic and nanofluidic RPS technologies within the last 6 years, ranging from some new phenomena, methods of improving the sensitivity and throughput, and their applications, to some popular nanopore or nanochannel fabrication techniques. The future research directions and challenges on microfluidic and nanofluidic RPS are also outlined.