Enhanced Bipolar Electrochemistry at Solid-State Micropores: Demonstration by Wireless Electrochemiluminescence Imaging

Abstract

Bipolar electrochemistry (BPE) is a powerful method based on the wireless polarization of a conductive object that induces the asymmetric electroactivity at its two extremities. A key physical limitation of BPE is the size of the conductive object because the shorter the object, the larger is the potential necessary for sufficient polarization. Micrometric and nanometric objects are thus extremely difficult to address by BPE due to the very high potentials required, in the order of tens of kV or more. Herein, the synergetic actions of BPE and of planar micropores integrated in a microfluidic device lead to the spatial confinement of the potential drop at the level of the solid-state micropore, and thus to a locally enhanced polarization of a bipolar electrode. Electrochemiluminescence (ECL) is emitted in half of the electroactive micropore and reveals the asymmetric polarization in this spatial restriction. Micrometric deoxidized silicon electrodes located in the micropore are polarized at a very low potential (7 V), which is more than 2 orders of magnitude lower compared to the classic bipolar configurations. This behavior is intrinsically associated with the unique properties of the micropores, where the sharp potential drop is focused. The presented approach offers exciting perspectives for BPE of micro/nano-objects, such as dynamic BPE with objects passing through the pores or wireless ECLemitting micropores.

Sensing with Nanopores and Aptamers: A Way Forward

“…In most surface functionalization, the whole surface of the nanopore membrane is covered inducing a loss in recognition specificity inside the pore for sensing applications. Interestingly, the ContactLess ElectroFunctionalization (CLEF) technique allows functionalizing with a large range of ligands (DNA, antibodies) only the inner part of the nanopore [ 118 , 119 , 120 , 121 ] which is a good strategy for enhancing the detection of protein with solid-state nanopore [ 122 ].…”

Intracellular Wireless Analysis of Single Cells by Bipolar Electrochemiluminescence Confined in a Nanopipette

“…The increase of the electric field strength could favor BPE, but it will induce simultaneously the electroporation of the cellular membrane and the lysis of the cell. Some recent studies at micro/nanopores have successfully exhibited a spatial confinement of voltage drop at these pores resulting in a locally enhanced polarization of a bipolar electrode . For example, Zhang et al.…”

Polarization Induced Electro-Functionalization of Pore Walls: A Contactless Technology

“…Recently, we adapted CLEF to these substrates by conceiving a wireless electrochemiluminescent (ECL) planar micropore in a microfluidic device ( Figure 10) [116]. The microfluidic conception combined with selective etching of the silicon oxide in the micropore region permitted using two orders of magnitude lower voltages for generating ECL signals from the silicon micropore compared to standard bipolar electrochemistry setups.…”

“…The ease of making a series of planar pores, possible combination with other lab-on-a-chip functions such as sample pretreatment, and/or parallelization of functionalized pore sensors open the way to new kinds of biosensing platforms for multiplexing. Recently, we adapted CLEF to these substrates by conceiving a wireless electrochemiluminescent (ECL) planar micropore in a microfluidic device ( Figure 10) [116]. The microfluidic conception combined with selective etching of the silicon oxide in the micropore region permitted using two orders of magnitude lower voltages for generating ECL signals from the silicon micropore compared to standard bipolar electrochemistry setups.…”