Performance improvement of plasmonic sensors using a combination of AC electrokinetic effects for (bio)target capture

Abstract

Analytes concentration techniques are being developed with the appealing expectation to boost the performance of biosensors. One promising method lies in the use of electrokinetic forces. We present hereafter a new design for a microstructured plasmonic sensor which is obtained by conventional microfabrication techniques, and which can easily be adapted on a classical surface plasmon resonance imaging (SPRI) system without further significant modification. Dielectrophoretic trapping and electro‐osmotic displacement of the targets in the scanned fluid are performed through interdigitated 200 μm wide gold electrodes that also act as the SPR‐sensing substrate. We demonstrate the efficiency of our device's collection capabilities for objects of different sizes (200 nm and 1 μm PS beads, as well as 5–10 μm yeast cells). SPRI is relevant for the spatial analysis of the mass accumulation at the electrode surface. We demonstrate that our device overcomes the diffusion limit encountered in classical SPR sensors thanks to rapid collection capabilities (<1 min) and we show a consequent improvement of the detection limit, by a factor >300. This study of an original device combining SPRI and electrokinetic forces paves the way to the development of fully integrated active plasmonic sensors with direct applications in life sciences, electrochemistry, environmental monitoring and agri‐food industry.

Dielectrophoretic cell trapping for improved surface plasmon resonance imaging sensing

“…The SPR signal enhancement of microparticles under DEP forces and ACEO flow generated by coplanar IDE has been previously studied in our group and reported elsewhere . However, with this configuration, particles far away from the electrodes will be less responsive to the DEP forces, due to the rapid electric field decay with the distance from the electrodes.…”

Rapid fabrication of interdigitated electrodes by laser ablation with application to electrokinetically enhanced surface plasmon resonance imaging

“…Interdigitated electrodes -intermeshed, individually addressable planar electrodes -have been demonstrated in a wide variety of applications including biosensing 1,2 , cell-sorting 3 , diagnostics 4 , and petrochemistry 5 ; making use of transduction mechanisms either inherent to the electrodes themselves (e.g., impedance 4,5 or capacitance based methods [6][7][8] ) or in adjacent transducers near which the IDEs concentrate an analyte by electrokinetic mass transport. 9,10 When employed for mass transport, IDEs can leverage electrokinetic effects such as dielectrophoresis (DEP), alternating current electro-osmosis (ACEO), and the electro-thermal effect (ETE) to concentrate and displace particulate matter in a carrier liquid as a function of the frequency and amplitude of oscillating electrical signals applied to the opposing electrodes. 9,10 Due to the polyvalent nature of IDEs, they are incorporated into a large variety of different devices.…”

“…9,10 When employed for mass transport, IDEs can leverage electrokinetic effects such as dielectrophoresis (DEP), alternating current electro-osmosis (ACEO), and the electro-thermal effect (ETE) to concentrate and displace particulate matter in a carrier liquid as a function of the frequency and amplitude of oscillating electrical signals applied to the opposing electrodes. 9,10 Due to the polyvalent nature of IDEs, they are incorporated into a large variety of different devices. As a result, it is common practise for researchers to fabricate the IDEs themselves in order to tailor the micro-patterned surfaces to their specific application.…”

“…As a result, it is common practise for researchers to fabricate the IDEs themselves in order to tailor the micro-patterned surfaces to their specific application. 5,[7][8][9]11 Traditionally, fabrication of electrodes necessitates some or all of: deposition of the electrode material and adhesion layers onto a suitable substrate, fabrication of a hard mask, and deposition of photoresist followed by lithography and associated wet or dry etching techniques. [12][13][14][15] Such methods are time-consuming, expensive, and incompatible with rapid iteration of component design, slowing the pace of research and obligating researchers to handle etchant chemicals and perform lengthy lithography processes and other steps which require skills that may be unrelated to their scientific training.…”

AC-Electroosmosis-Assisted Surface Plasmon Resonance Sensing for Enhancing Protein Signals with a Simple Kretschmann Configuration

“…ACEO is an electrokinetic phenomenon induced by the application of AC voltage to microelectrodes, causing circulating flow above the electrode surface that mixes the analyte solution near the surface and increases the chance of analyte molecules binding to the ligands on the surface [ 12 , 13 , 14 , 15 , 16 ]. The use of electrokinetic phenomena has been reported in the literature [ 17 , 18 ]; however, it requires a complex optical system for imaging sensor chips designed for SPR imaging [ 19 , 20 ], and the improvement of protein binding has not been proven with a sensing setup without imaging function. To broaden the application of electrokinetic effects in SPR sensing, the verification of the efficiency of ACEO in protein detection is reported here using a standard Kretchmann-type SPR sensing setup.…”