Abstract
This article demonstrated a chip device with alternating current (AC) dielectrophoresis (DEP) for separation of non-biological micro-particle and bacteria mixtures. The DEP separation was achieved by a pair of metal electrodes with the shape of radal-interdigital to generate a localized non-uniform AC electric field. The electric field and DEP force were firstly investigated by finite element methods (FEM). The mixed microparticles such as different scaled polystyrene (PS) beads, PS beads with inorganic micro-particles (e.g., ZnO and silica beads) and non-bioparticles with bacterial Staphylococcus aureus (S. aureus) were successfully separated at DEP-on-a-chip by an AC electric field of 20 kHz, 10 kHz and 1 MHz, respectively. The results indicated that DEP trapping can be considered as a potential candidate method for investigating the separation of biological mixtures, and may well prove to have a great impact on in situ monitoring of environmental and/or biological samples by DEP-on-a-chip.
Highlights
Dielectrophoresis (DEP) forces[1] are exible and can be modi ed by changing frequencies, which showed some advantages over other methods, i.e., label-free, ease of handling, high precision and being high speed
The particles should be trapped in a detection region before analysis, as the position of the particle has a big impact on the accuracy of the measurement results
If the frequency was set to above 1 MHz, a strong positive DEP (pDEP) force could be obtained for S. aureus bacteria trapping, which eliminating PS beads due to their negative DEP (nDEP) behaviors
Summary
Dielectrophoresis (DEP) forces[1] are exible and can be modi ed by changing frequencies, which showed some advantages over other methods, i.e., label-free, ease of handling, high precision and being high speed. DEP has attracted a great deal of attention to control particles due to its high selectivity and rapidity in manipulation.[2] It is based upon the fact that particles with different electrical characteristics will behave diversely in a non-uniform electric eld It has been used for trapping processes,[3] and for aligning,[4,5,6] isolating and separation various sized particles,[7,8] and applied in a wide range of medical research,[9,10] biological[11,12,13,14] and environmental[15] applications to analyze particles of interest. We presented a device with AC electric elds by a nonuniform microelectrode array, along the direction of electric eld intensity by much lower frequencies and applied voltages to pattern and separate particles It was demonstrated respectively in separation of colloidal PS beads by size, PS beads and inorganic micro-particle (silica and ZnO beads) and bioparticles (S. aureus). The key parameter, electrical conductivity of a solid homogeneous PS bead, can be expressed as sp ss þ
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