Joule heating-induced particle manipulation on a microfluidic chip

Abstract

We develop an electrokinetic technique that continuously manipulates colloidal particles to concentrate into patterned particulate groups in an energy efficient way, by exclusive harnessing of the intrinsic Joule heating effects. Our technique exploits the alternating current electrothermal flow phenomenon which is generated due to the interaction between non-uniform electric and thermal fields. Highly non-uniform electric field generates sharp temperature gradients by generating spatially-varying Joule heat that varies along radial direction from a concentrated point hotspot. Sharp temperature gradients induce local variation in electric properties which, in turn, generate strong electrothermal vortex. The imposed fluid flow brings the colloidal particles at the centre of the hotspot and enables particle aggregation. Further, manoeuvering structures of the Joule heating spots, different patterns of particle clustering may be formed in a low power budget, thus, opening up a new realm of on-chip particle manipulation process without necessitating highly focused laser beam which is much complicated and demands higher power budget. This technique can find its use in Lab-on-a-chip devices to manipulate particle groups, including biological cells.

Strong rotating flow in stationary droplets in low power budget using wire electrode configuration

“…Thus, as a leading role electrothermal forces generate the circulations in the droplets and promote efficient mixing ability. Such electrothermal motion were applied in the operations of fluid pumping , mixing of analytes , controlling two‐phase flow , and particle manipulation . Based on the above description of the governing equations, we have performed numerical simulation to understand the flow field and thermal field.…”

“…Thus, as a leading role electrothermal forces generate the circulations in the droplets and promote efficient mixing ability. Such electrothermal motion were applied in the operations of fluid pumping [43,44], mixing of analytes [45,46], controlling twophase flow [47,48], and particle manipulation [49,50]. Based Table 1.…”

On‐Chip Generation of Vortical Flows for Microfluidic Centrifugation

“…Since the local temperature gradient ∇ T scales as σV 2 /κ from an order‐of‐magnitude approximation of the energy conservation equation, in which V is the applied voltage and κ the thermal conductivity of the fluid, it then follows that < F e > ∼ E 2 ∇ T ∼ E 4 . Such localized temperature gradients have been shown to give rise to a vortical flow, which can be combined with dielectrophoretic trapping to enable particle aggregation and trapping ( Figure ) …”

“…• AC electroosmotic flow -Capacitive charging [67][68][69][70] -Faradaic charging [68,71,72] Electrothermal effect [73][74][75][76][77][78][79][80][81][82] Interfacial electrokinetics…”

“…Such localized temperature gradients have been shown to give rise to a vortical flow, which can be combined with dielectrophoretic trapping to enable particle aggregation and trapping (Figure 20). [78,[80][81][82]…”