Microchannels formed in non-conductive substrates like fused silica, glass and quartz, etc, have wide applications in the field of micro-fluidic and lab-on-chip applications due to their optical transparency, chemical inertness, and biocompatible nature. Electrochemical discharge machining (ECDM) has emerged as a potential low-cost fabrication method to fabricate microfeatures in these materials, compared to conventional laser etching techniques. In this paper, numerical simulation and experimental fabrication of microchannels in a glass substrate using the ECDM based micromilling technique is demonstrated. Stainless steel needle as tool electrode is used in alkaline electrolyte medium. The effects of process parameters viz. tool feed rate, pulse frequency and machining voltage on material removal rate (MRR) and surface roughness (SR) of the microchannels were analysed. The experimental results showed that the MRR and SR increases with an increase in machining voltage and tool feed rate but reduces with an increase in the pulse frequency. Simulations using FEM-based model showed similar trends in MRR with that of experiments. A comparison between the cross-section profiles obtained by the experimental work and predicted profile by the numerical simulation showed some deviation between them due to the Gaussian heat flux assumption in the numerical model. Optical images showed that KOH performance is comparatively better than NaOH with respect to thermal damage and width of cut. Further, multi-objective optimization was performed using utility theory coupled with Taguchi’s method to optimize the process parameters. Moreover, the capability of the ECDM process was demonstrated in fabricating various other micro-features such as sinusoidal channel, letter engraving, etc in a glass substrate, which can be extended to other brittle materials like quartz, fused silica, ceramic, etc.

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Fabrication of deep microchannels by a simple electrochemical discharge based multi-pass micromilling technique is reported. The effect of electrolyte concentration, tool feed rate, number of passes, and power supply on the geometric characteristics of the microchannel is presented. Numerical analysis was performed to predict the shapes and sizes of the microchannels, which matched quite well with the experimental values. An increment in the channel depth was observed with an increase in the machining voltage and the total number of passes. Through-channels were etched in a 400 μm thick glass substrate at machining voltages of 55 V and 60 V after the 6th and 5th pass respectively using a 10% KOH electrolyte. For deeper microchannels (>500μm), a higher electrolyte concentration, i.e., 30% was required, that had enhanced chemical etching, resulting in higher depth and relatively smooth channel surface. Microchannels having depth >1100 μm was obtained with a 30% KOH electrolyte concentration after the 16th pass. The number of passes required to achieve higher channel depth depends on the combined effect of voltage and the electrolyte concentration. The tool wear rate was higher at higher machining voltages. Moderate machining voltage, pulse frequency, and higher concentration are recommended for deep glass micromachining applications.

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