Methods for counting particles in microfluidic applications

Abstract

Microfluidic particle counters are important tools in biomedical diagnostic applications such as flow cytometry analysis. Major methods of counting particles in microfluidic devices are reviewed in this paper. The microfluidic resistive pulse sensor advances in sensitivity over the traditional Coulter counter by improving signal amplification and noise reduction techniques. Nanoporebased methods are used for single DNA molecule analysis and the capacitance counter is useful in liquids of low electrical conductivity and in sensing the changes of cell contents. Light-scattering and light-blocking counters are better for detecting larger particles or concentrated particles. Methods of using fluorescence detection have the capability for differentiating particles of similar sizes but different types that are labeled with different fluorescent dyes. The micro particle image velocimetry method has also been used for detecting and analyzing particles in a flow field. The general limitation of microfluidic particle counters is the low throughput which needs to be improved in the future. The integration of two or more existing microfluidic particle counting techniques is required for many practical on-chip applications.

Thermal Measurement Techniques in Analytical Microfluidic Devices

“…Detecting and counting particles in microfluidic devices is widely used for environmental, industrial, and biological applications 1 . TPD is one of the novel applications of thermal measurements in microfluidic devices 2 .…”

Spatially dependent diffusion coefficient as a model for pH sensitive microgel particles in microchannels

“…An important feature of biomicrofluidic devices [1][2][3][4][5][6][7] is that the fluid flow is laminar. 8,9 Adjacent flow streams translate by advection without significant mixing, and solutes in the adjacent streams only intermingle via the process of diffusion, which is therefore an especially important mechanism of particle transport on the microscale.…”

“…[39][40][41] We focus here on the latter type as the variation of MG size with pH can be well controlled. This is an important stimulus for MG as they are used as biosensors [5][6][7] and as drug delivery agents whose function depends on pH. 42 A microgel particle subject to a pH gradient, pHðRÞ, can cause its diameter, r, to be RÀ dependent, reflecting the local pH value.…”

Particle Accumulation by AC Electroosmosis in Microfluidic Device with Co-Planar Electrodes

“…The microfluidic platform has advantages such as (a) relatively rapid reaction, (b) minute consumption of samples, (c) potential for cost-effective and portable chip, and (d) availability of multi-functional integration within a device. An enhancement of detection or measurement for small particles dispersed in a solution is one of essential issues to be developed for finding the way of industrial applications, especially portable in-field sensing and point-of-care diagnostics (6) . A simple method to control the local concentration of particles to a specific area in a device enables an easy and cost-effective sensing.…”