The Dielectrophoresis Network
at the University of Surrey
Dielectrophoresis is a phenomenon that was first described over a hundred years ago, and first understood in the 1950s. However, despite numerous examples of the advantages of dielectrophoresis in cell sorting and analysis, there has yet to be a significant uptake of the technology beyond academic enthusiasts with an interest in the phenomenon. As a group, it has been our primary motivating aim to develop DEP technology that can be readily applied to real-world problems - systems which are inherently simple to sue, high-throguhput and low-cost.
In 2003, we developed a new method of analysing cells, using structures constructed on entirely new principles. Rather than being based on two-dimensional electrodes, the Surrey system was constructed in three dimensions; these improved the volume of cells that could be analysed simultaneously (to thousands) whilst dramatically simplifying the analysis process. The chips required for measurement would be orders of magnitude cheaper to produce than their predecessors, whilst their analysis could be completely automated. The new system offers a potential revolution in cell biology, from analysis to diagnosis, because for the first time the study of electrophysiology can become routine.
The patented three-dimensional electrodes (which we refer to as DEP-Wells) represent a significant technological advance in DEP. The 3D structure presents a dramatic increases in electrode area around a given volume allowing larger volumes to be processed, increasing performance and improving the ease of handling compared to conventional DEP electrodes. Higher volume and the ability to construct arrays in highly parallel well plate formats familiar to the laboratory environment will mean huge increases in the utility, throughput and convenience of DEP and the concomitant savings in time and consumable costs for the customer when compared to current methods.
The 3DEP system consists of two parts, the DEP-well chip and the 3DEP reader system. The chips are constructed of multiple alternating layers of conductors and insulators which, when drilled, form wells (typically 1mm across) with electrode “stripes” down the side. When the electrodes are energised, the dielectrophoretic force causes cells to move either towards or away from the edges, meaning that examining the way in which light passing through the well can determine the polarisability at that frequency. The chip is easy to manufacture in large quantities, and can be produced in different sizes or different applications (though the existing variant has served well in analysing cells from bacteria (1µm diameter to heart muscle cells (50µm diameter). Controlling this chip is a stand-alone reader system we call the 3DEP. Containing 20 signal generators, each individually controllable for frequency (up to 50MHz) and voltage (up to 10V), plus all of the associated optics and connectivity equipment; the chip is simply slotted into the device, the door closed, and the experiment run. Control and data analysis are provided by an accompanying PC, and the whole system is controlled via USB. Among the benefits of the system is that of speed - high-quality DEP spectra can be obtained in as little as ten seconds, opening new vistas of applications.
We have also developed quasi-2D versions of the DEP-Wells, called DEP-Dots. These use the same principles but are compressed into a single electrode layer and a transparent counterelectrode. The DEP-Dot geometry has also been patented, and has proven useful in cell characterisation in very small volumes using similar principles to the DEP-Wells. Furthermore, the DEP-Dot geometry has been very useful for cell patterning in hydrogels - more in the Stem Cells and Tissue Engineering section.
Key papers from our archive:
DEP-Wells: 31, 32, 45, 52, 62
DEP-Dots: 43, 49, 59