Electrochemical etching of carbon materials: Applications in microfabrication, electroanalysis and electrospray mass spectrometry

The research presented in this work explores the implementation of electrochemical etching to graphitic carbon materials, with a broad focus on the fields of microfabrication, electroanalysis and mass spectrometry. A method is presented for the etching of glassy carbon (GC) and pyrolyzed photoresist films (PPF) that opens pathways enabling the creation of new devices and electrode patterns. This was accomplished through standard lithography to transfer a pattern onto a photoresist layer and electrochemical oxidation of the exposed graphitic surface in basic electrolyte. The reaction at the carbon electrode results in the breakdown of the carbon lattice, which likely involves the intercalation of hydroxide anions. The depth achieved during etching was found to be dependent on the applied potential, anodization time, and the charge that is delivered during the anodization. The presented etching process was found to be isotropic due to the nano-scale graphitic microcrystalline size of GC.; Three proposed applications for the electrochemical etching of carbon material are explored and presented through the design and characterization of various structures in carbon material. The first application illustrates the fabrication of microchannel structures. This represents the first time that a wet etching method has been used in the fabrication of structures into carbon material. The second application involved the electrochemical fabrication and characterization of arrays of sub-micron sized carbon electrodes and band electrodes for their potential use in electroanalysis. Finally, design, fabrication, and operation of a GC microchip interfaced to nanoelectrospray ionization mass spectrometry was explored. This platform was designed to be coupled to an external separation technique, followed by on-chip ionization and spray, culminating in quadrupole mass spectrometric identification of the sample. By analysis of the outlined applications, the electrochemical etching method is presented as a feasible mode of carbon microfabrication.