Floating-electrode enhanced constriction dielectrophoresis for biomolecular trapping in physiological media of high conductivity

Abstract

We present an electrokinetic framework for designing insulator constriction-based dielectrophoresis devices with enhanced ability to trap nanoscale biomolecules in physiological media of high conductivity, through coupling short-range dielectrophoresis forces with long-range electrothermal flow. While a 500-fold constriction enables field focusing sufficient to trap nanoscale biomolecules by dielectrophoresis, the extent of this high-field region is enhanced through coupling the constriction to an electrically floating sensor electrode at the constriction floor. However, the enhanced localized fields due to the constriction and enhanced current within saline media of high conductivity (1 S/m) cause a rise in temperature due to Joule heating, resulting in a hotspot region midway within the channel depth at the constriction center, with temperatures of $8 -10 K above the ambient. While the resulting vortices from electrothermal flow are directed away from the hotspot region to oppose dielectrophoretic trapping, they also cause a downward and inward flow towards the electrode edges at the constriction floor. This assists biomolecular trapping at the sensor electrode through enabling long-range fluid sampling as well as through localized stirring by fluid circulation in its vicinity.

Tuning direct current streaming dielectrophoresis of proteins

“…Although our experiments are carried out at low buffer conductivity, our work complements protein DEP studies under physiological conditions in nm-sized constriction devices, in which trapping was observed. 32,33 Thus, the resulting optimum pH range for iDEP as observed here is well suited for applications combining DEP manipulation with biological FIG. 2.…”

“…Furthermore, temperature effects are likely to occur due to the high electric fields employed promoting aggregation in DEP experiments. 32 Thus, various factors may significantly alter DEP behavior of proteins in analytical microfluidic devices. To the best of our knowledge, a thorough investigation of these effects influencing protein DEP has not been conducted previously and is important for future applications involving immunoglobulins.…”

“…19,[26][27][28][29][30][31][32] This is not only due to the particular special arrangements at the microscale used to generate high electric field gradients, but also a consequence of the solvent conditions and intrinsic protein properties. Moreover, a generic theoretical model predicting protein polarizability and accounting for the large protein variety has not been developed yet.…”

“…19 H€ olzel et al showed the DEP induced trapping of the large multimeric protein R-phycoerythrin at metal electrode gaps; 30 whereas Bakewell et al investigated frequency dependent DEP behavior of avidin. 31 Recently, an iDEP device 29 as well as a constriction device 32,33 was employed to trap proteins.…”

On-chip DNA preconcentration in different media conductivities by electrodeless dielectrophoresis

“…Simulation work on electrokinetics and dielectrophoresis was reported in which it trapped nanoscale biomolecules in physiological media of high conductivity. 20 Recently, Chia-Fu Chou's group demonstrated the trapping of protein and DNA by nanoconstriction. [21][22][23] The requirements of time-consuming fabrication of nano-constriction (e.g., ebeam lithography) and the high electric field strength are inevitable.…”