Based on sophisticated nanofabrication techniques, we manufacture plenty of micro/nanoscale devices, e.g., nanopores/channels, microfluidic chips, and polymer membranes, for electrochemical measurements to unearth unique phenomena at the nanoscale and seek valuable applications. As an example, highly-dense, parallel nanopore electrode arrays (NEAs), composed of 1–3 nanoelectrodes embedded into nanopores (diameter ~ 10–500 nm), are fabricated to investigate nanoelectrochemical characteristics in confined volumes, typ. V = 10-18 L. NEAs have been exploited for a range of studies including ion/molecular transport and current amplification/rectification.

With hierarchically organized nanopore arrays, we investigate ion/molecular transport behaviors to demonstrate selective and sensitive electrochemical detections. A biomimetic pH-responsive, charge-selective dual-gating is demonstrated in block copolymer-coated NEAs (BCP@NEAs). The BCP membrane serves as a pH-responsive on/off gate controlling ion transfer into the nanopores and redox species are selectively transported and sensitively detected via signal amplification. Furthermore, potential-induced wetting and dewetting behavior is investigated in hydrophobic nanochannels for mass transport controls. Moreover, electrochemical transistor operation is realized in 3-electrode-embedded NEAs based on electrowetting phenomena inside defect-mediated SiNx nanochannels.

NEAs are utilized as a bifunctional electrochemical zero-mode waveguide (E-ZMW), which is a powerful tool for studying single redox enzymes by means of electrochemical and spectroscopic measurements in massively parallel format - many copies of single entities. Real-time potential-dependent fluorescence responses of single enzyme molecules are investigated in the E-ZMWs, which generate zeptoliter scale observation volume by confining optical radiation within the nanopores. Externally controlled potentials are able to manipulate the redox state of biomolecules. Fluorescence dynamics are monitored by correlating electrochemical and spectroscopic signals at single molecule occupancy under a variety of reaction perturbations.

NEAs are applied for highly sensitive electrochemical detection and real-time monitoring of phenazine metabolites produced by P. aeruginosa. This strategy further extends to selective detection of bacterial metabolite by combining electrochemistry with surface-enhanced Raman spectroscopy.

One of our research interests focuses on electrochemical energy conversion system and applications. Miniaturized flexible patch-type reverse electrodialysis (RED) is devised for low electric power sources. By integrating disposable RED with a bipolar electrode on a microfluidic chip, electrochemiluminescence-based biosensing platform is developed. For transdermal drug delivery, a biocompatible, wearable RED patch successfully demonstrates facilitated delivery of ionic drugs through skins.

By scanning electrochemical microscopic tecniques, we investigate catalytic electrchemical reactions and biological processes by exploring real time spatially-resolved catalytic kinetics and mass transport behaviors of product generated at interfaces.