Detection Of Bioparticles Research Articles

A micromachined high throughput Coulter counter for bioparticle detection and counting

We describe a micromachined Coulter counter with multiple sensing microchannels for quantitative measurement of polymethacrylate particles and pollen. A unique design with sensing microelectrodes in the center of the microchannels is demonstrated. This design creates isolation resistances among channels, and thus circumvents the crosstalk caused by automatic electrical connection among microchannels. When implemented using microfluidic channels, this design is appropriate for the sensing of microscale particles in deionized water or in dilute electrolyte solution. Our design has multiple channels operating in parallel, but integrated with just one sample reservoir and one power source. The results with a four-channel device show that this device is capable of differentiating and counting micro polymethacrylate particles and Juniper pollen rapidly. Moreover, the device throughput is improved significantly in comparison to a single-channel device. The concept can be extended to a large number of sensing channels in a single chip for significant improvement in throughput.

Numerical design of a 3-D microsystem for bioparticle dielectrophoresis: The Pyramidal Microdevice

A device for the detection of bioparticles (latex beads, cells, proteins, DNA,…) present in a small volume of a liquid sample is described. Dielectrophoresis (DEP) is used to enhance the transport of bioparticles towards the reactive surface of the detector. A Pyramidal Microdevice (PM) is designed using numerical simulation. Unlike conventional coplanar electrode microchips, this original 3D configuration is able to collect particles on a surface for both positive and negative DEP. Numerical simulations show the location of the collection zones in the PM according to the DEP mode applied. PM performance is evaluated with the calculation of the collection kinetics. The influence of the voltage is studied. Experiments on PM with latex microparticles confirm calculations. Their replacement by DNA molecules attests to the feasibility of a PM collecting such extremely small particles using DEP.

Biased AC electro-osmosis for on-chip bioparticle processing

Real-time detection of bioparticles is of great importance in deterring infectious diseases and bioterrorism. For bioparticle solutions with concentrations at an infectious level, culturing is typically used to increase the particle concentration to a detectable level, which is time consuming and often unfeasible under field conditions. Therefore, a real-time particle concentration technique is in demand to bridge the gap between the detectable level and infectious level of bacterial solutions. This paper describes a novel electrokinetic method that can potentially concentrate particles in real time. By studying surface flows on planar electrode pairs, two distinct ac electro-osmosis (ACEO) flows have been identified which are due, respectively, to capacitive and Faradaic charging of electrode double layers. Biased ACEO, combining dc bias with ac signals, breaks the symmetry of electrode charging, leading to asymmetric surface flows and a variety of directed surface flows that can concentrate, manipulate, and transport particles. Surface flows of opposite directions on planar electrodes produce stagnation lines that function as long-range particle traps and lead to net flows for micropumping. The device fabrication and operation are simple and compatible with integrated circuit technology

Continuous recording of blood oxygen tensions by polarography.

Continuous recording of blood oxygen tensions by polarography.