Rapid and sensitive detection of small biomolecule by capacitive sensing and low field AC electrothermal effect

Abstract

Conventional affinity biosensor typically relies on passive diffusion of analytes for binding reaction, which in many cases leads to long response time and lack of sensitivity. Recent research showed that directed particle motion towards sensor electrodes could be induced in sample matrix by applying an inhomogeneous AC electric field, often with AC dielectrophoresis as the responsible mechanism. As a result, shorter assay time and higher sensitivity can be achieved. Previously, we demonstrated a rapid and sensitive AC capacitive affinity sensor, which integrates low voltage AC dielectrophoresis into label-free capacitive measurement to achieve a single-step operation without any wash steps for clinical samples. However, dielectrophoretic force is rather short-ranged, and is also proportional to the size of target biomolecules/particles. Therefore, to detect target molecule at diluted concentrations or small molecule, improvement in sensitivity by dielectrophoresis could be quite limited. Alternatively, AC electric field can also produce microfluidic movement to carry biomolecules to sensors, which is of long range and size independent. This work demonstrates the use of low voltage AC electrothermal effect to enhance and accelerate the detection of low abundance and small target molecules by AC capacitive sensing with simultaneous AC electrokinetic enrichment. Electrode designs were studied for their effectiveness in AC electrothermal capacitive sensing. Electrodes with larger characteristic length were found to be more amenable to inducing AC electrothermal convection and were successfully used to detect low abundance protein and femto-molar level small molecules.

Real-time Sensing of Trace Biomarkers from Viruses with a Microfluidic Immunosensor: A Case Study of SARS-CoV-2 Detection in Cold-chain Food

“…For trace particle detection in liquid, the pre-concentration of target particles is always crucial to a successful test [33][34][35]. Compared with most techniques for pre-concentration needing an extra incubation or equipment, AC electrokinetic (ACEK) effects can manipulate nanoparticles efficiently to realize target enrichment rapidly without extra processes or devices [36][37][38]. For relatively large molecules such as proteins, dielectrophoresis (DEP) force, an important ACEK effect, has been demonstrated as a dominant force applied on the particles [39,40].…”

Rapid detection of trace Cu2+ using an l‐cysteine based interdigitated electrode sensor integrated with AC electrokinetic enrichment

“…Below a few MHz, ACET effect depends on electric field and solution conductivity at room temperature. The expression of ACET force is approximated to be : where σ m is the conductivity of the solution, k is the is the thermal conductivity of the solution, and R is half of the electrode gap.…”

Microfluidic Studies of Polymer Adsorption in Flow

“…Electrokinetic forces inducing microflow have been used to increase the binding rate of goat anti‐bovine IgG to surface‐immobilized bovine IgG . Planar interdigitated microelectrodes with three different dimensions were bonded to a silicone microchamber, and functionalized with bovine IgG protein (Figure b).…”