Rapid and Sensitive Detection of Nanomolecules by an AC Electrothermal Flow Facilitated Impedance Immunosensor

Abstract

Conventional immunosensors typically rely on passive diffusion dominated transport of analytes for binding reaction and hence, it is limited by low sensitivity and long detection times. We report a simple and efficient impedance sensing method that can be utilized to overcome both sensitivity and diffusion limitations of immunosensors. This method incorporates the structural advantage of nanorod-covered interdigitated electrodes and the microstirring effect of AC electrothermal flow (ACET) with impedance spectroscopy. ACET flow induced by a biased AC electric field can rapidly convect the analyte onto nanorod structured electrodes within a few seconds and enriches the number of binding molecules because of excessive effective surface area. We performed numerical simulations to investigate the effect of ACET flow on the biosensor performance. The results indicated that AC bias to the side electrodes could induce fast convective flow, which facilitates the transport of the target molecules to the binding region located in the middle as a floating electrode. The temperature rise due to the Joule heating effect was measured using a thermoreflectance imaging method to find the optimum device operation conditions. The change of impedance caused by the receptors-target molecules binding at the sample/electrode interface was experimentally measured and quantified in real-time using the impedance spectroscopy technique. We observed that the impedance sensing method exhibited extremely fast response compared with those under no bias conditions. The measured impedance change can reach saturation in a minute. Compared to the conventional incubation method, the ACET flow enhanced method is faster in its reaction time, and the detection limit can be reduced to 1 ng/ml.In this work, we demonstrate that this sensor technology is promising and reliable for rapid, sensitive, and real-time monitoring biomolecules in biologically relevant media such as blood, urine, and saliva.

Review of nonlinear electrokinetic flows in insulator‐based dielectrophoresis: From induced charge to Joule heating effects

“…More studies are needed to understand accurately the interplay of ICEO and electrothermal flows, which will aid the optimal design and operation of future iDEP microdevices. More applications are expected on the way for ICEO (e.g., [157][158][159]) and electrothermal [160][161][162][163][164][165] flows that are not necessarily limited to iDEP microdevices. To move forward, there are some research directions in the field, which, from this author's view, may be worthy of further investigations and are outlined below.…”

Dielectric Characterization and Multistage Separation of Various Cells via Dielectrophoresis in a Bipolar Electrode Arrayed Device

“…24 Electric properties of separation buffer, involving conductivity and dielectric permittivity, will have an evident response for varying local temperatures 30,31 as a result of Joule heating in the buffer. A dielectric gradient generates in the buffer, giving rise to a volume force on the bulk liquid 32,33…”

“…Electric properties of separation buffer, involving conductivity and dielectric permittivity, will have an evident response for varying local temperatures , as a result of Joule heating in the buffer. A dielectric gradient generates in the buffer, giving rise to a volume force on the bulk liquid , where T indicates the temperature, and σ­( T ) and ε­( T ) are the fluid conductivity and permittivity at different temperatures, respectively. Consequently, bulk electroconvection occurs in the channel.…”

Clinical detection of neurodegenerative blood biomarkers using graphene immunosensor

“…Detection of multiple biomarkers or other proteins can then be achieved in a single run [174], allowing faster screening times, lower equipment cost and enabling pointof-care diagnosis [175]. To achieve multiplexed functionality, electrical signal traces (conductors) can be patterned or deposited over the sensing area [176], with the measurement interface adjacent (2D sensor array) or within a different geometry level (3D array).…”