Jeong-Il Heo

Carbon Interdigitated Array Nanoelectrodes for Electrochemical Applications

Redox current amplification has been demonstrated using carbon interdigitated array IDA nanoelectrodes derived from precursorpolymer microstructures through conventional photolithography and pyrolysis. This simple conversion process, also known ascarbon-microelectromechanical systems, enables nanometer-level fabrication of carbon materials in a reproducible and an eco-nomic manner. We demonstrated that with carbon IDA nanoelectrodes fabricated in two mask processes a current amplificationfactor of 25 can be obtained. This high amplification factor is a result of the efficient recycling of redox species between the 1:1aspect ratio carbon nanoelectrodes. This type of a current amplification value is hard to obtain when using more traditional flatnanometer level spaced noble metal IDA electrodes fabricated with more expensive nanopatterning processes such as E-beamlithography.© 2011 The Electrochemical Society. DOI: 10.1149/1.3531952 All rights reserved.Manuscript submitted July 7, 2010; revised manuscript received September 25, 2010. Published January 13, 2011.

Monolithic carbon structures including suspended single nanowires and nanomeshes as a sensor platform

With the development of nanomaterial-based nanodevices, it became inevitable to develop cost-effective and simple nanofabrication technologies enabling the formation of nanomaterial assembly in a controllable manner. Herein, we present suspended monolithic carbon single nanowires and nanomeshes bridging two bulk carbon posts, fabricated in a designed manner using two successive UV exposure steps and a single pyrolysis step. The pyrolysis step is accompanied with a significant volume reduction, resulting in the shrinkage of micro-sized photoresist structures into nanoscale carbon structures. Even with the significant elongation of the suspended carbon nanowire induced by the volume reduction of the bulk carbon posts, the resultant tensional stress along the nanowire is not significant but grows along the wire thickness; this tensional stress gradient and the bent supports of the bridge-like carbon nanowire enhance structural robustness and alleviate the stiction problem that suspended nanostructures frequently experience. The feasibility of the suspended carbon nanostructures as a sensor platform was demonstrated by testing its electrochemical behavior, conductivity-temperature relationship, and hydrogen gas sensing capability.

Scalable suspended carbon nanowire meshes as ultrasensitive electrochemical sensing platforms

This paper presents novel electrochemical sensing platforms consisting of a set of a suspended carbon nanowire mesh electrode of deliberately controlled shape (hexagonal or diamond) and a planar carbon electrode located just below the suspended electrode that achieved the electrochemical current signal amplification of 120 times in a micro-channel by redox cycling of redox species. The carbon sensing platform was fabricated using only series of photolithography and pyrolysis processes which are known as Carbon-MEMS processes enabling production of carbon nano-structures in designed manner without using expensive nanolithography tools. The functionality of the stacked carbon nanoelectrodes were studied using cyclic voltammetry.