Silicon insulator‐based dielectrophoresis devices for minimized heating effects

Abstract

Concentration of biological specimens that are extremely dilute in a solution is of paramount importance for their detection. Microfluidic chips based on insulator-based DEP (iDEP) have been used to selectively concentrate bacteria and viruses. iDEP biochips are currently fabricated with glass or polymer substrates to allow for high electric fields within the channels. Joule heating is a well-known problem in these substrates and can lead to decreased throughput and even device failure. In this work, we present, for the first time, highly efficient trapping and separation of particles in DC iDEP devices that are fabricated on silicon using a single-etch-step three-dimensional microfabrication process with greatly improved heat dissipation properties. Fabrication in silicon allows for greater heat dissipation for identical geometries and operating conditions. The 3D fabrication allows for higher performance at lower applied potentials. Thermal measurements were performed on both the presented silicon chips and previously published PDMS devices comprised of microposts. Trapping and separation of 1 and 2 μm polystyrene particles was demonstrated. These results demonstrate the feasibility of high-performance silicon iDEP devices for the next generation of sorting and concentration microsystems.

Three dimensional passivated-electrode insulator-based dielectrophoresis

“…15,31 In our previous work with 3D iDEP devices fabricated on a silicon substrate, we reported 50% selective trapping of 1 lm and 2 lm beads in a high conductivity 20.0 mS/m solution at 100 V DC applied signal. 16 In this study, however, significant trapping of S. aureus bacteria at low signal amplitudes with electrodes capacitively coupled through a glass slide has been demonstrated. This 3D pDEP device achieves low voltage trapping while maintaining high trapping efficiency over a wide range of frequencies.…”

“…We have shown in the past that DC iDEP devices with 3D gradients generate stronger DEP forces in comparison to 2D gradient iDEP devices. 16 Similarly, the new 3D pDEP devices can operate at lower applied voltages which ultimately decreases Joule heating complications that usually plague iDEP devices. 24 Additionally, this limits electrothermal flow, which is a parasitic effect that creates complications in iDEP devices.…”

“…15 Earlier work, by our group, focused on trapping and separation of particles using silicon DC-Biased iDEP devices. 16 Furthermore, because silicon microfluidic devices were investigated in comparison to polymer devices, this study demonstrated greatly improved heat dissipation effects attributed to enhanced thermal dissipation properties of silicon over polymer substrates.…”

Off-chip passivated-electrode, insulator-based dielectrophoresis (OπDEP)

“…Even though we have used microposts design, any iDEP microchannel configuration can be employed with this technology, including single constrictions [24], 3D constrictions [25–27], 3D barriers [28], and filter designs [29]. DEP deflection-based devices [12, 30–32], which operate continuously with lower DEP forces, are straightforward to implement with OπDEP.…”

Joule heating effects on reservoir‐based dielectrophoresis

“…The PDMS film is 10 and 500 μm thick in the two microchips, respectively, through which Joule heating is dissipated at different rates. The thicker the film, the stronger the Joule heating effects are due to the low thermal conductivity of PDMS . It is important to note that the PDMS–PDMS configuration ensures uniform and identical surface properties between the two microchips.…”