Numerical methods for DEP modelling for lab-on-chips devices

The physical manipulation of biological cells is of vital importance in the development of laboratory operations on a small scale using miniaturized (lab-on-a-chip) devices. Microsystems devices is very appealing.because small volumes reduce the time taken to synthesize and analyse a product. Moreover these compact devices create new opportunities for the spatial and temporal control of cell growth and stimuli and allow samples to be analysed at the point of need rather than an usual laboratory.

Dielectrophoresis (DEP) has been reported as a promising method for cell manipulation without physical contact in miniaturized devices since it exploits the dielectric properties of cells suspended in a fluid and subjected to a variable gradient electric field E. In particular, DEP exploits the dielectric properties of cells, suspended in a buffer medium, undergoing the action of high-gradient electric fields. Then, the spatially non-uniform electric-field induces particle polarization: particles with higher polarizability than that of the surrounding medium experience positive DEP (pDEP), moving towards regions with high electric field, whereas particles less polarized than the surrounding medium experience negative DEP (nDEP), moving towards regions of low electric field.

figura_naldiLab-on-chip devices based on DEP phenomena could represent the miniaturized solution for carrying on complex experimental biological experiments. A group at the STMicroelectronics (STM) work in order to develop a modular, dielectrophoretic micro-fluidic platform, based on a silicon substrate, for different kinds of cell manipulation, suitable for lab-on-chip integration. In this work it is demonstrated that the nonuniform electric field required for cell manipulation could be generated by microelectrodes, patterned on the silicon substrate using standard microfabrication techniques, using several electrode geometries as bar array, fishbone-like array, spiral array, and quadrupole configuration. Moreover, numerical results obtained by finite element analyses were found in agreement with experimental data from DEP-based separation tests on some cell models. Within a collaboration between the ADAMSS Centre at Università degli Studi di Milano (Italy) and STM at Agrate Brianza, Italy, we are we have developed, studied, and compared different numerical methods in order to compute DEP force depending on the electrical field non-uniformity factor and in the case of the cellular aggregate with different dimensions. Furthermore, we performed a comparison between experimental and simulated results for some particular cell types and electrodes configurations.

Our results represent a good starting point in order to optimise the microelectrode configuration and to determine the DEP forces acting on cellular aggregates which are useful in biomedical applications.