Drilling microscopic holes in brittle materials like glass and ceramics, essential for smartphones, medical devices, and microfluidic chips, has long posed a challenge for manufacturers. Conventional methods often crack the material or fail when debris clogs narrow, deep holes. Researchers at the Indian Institute of Technology (IIT) Bombay have demonstrated how ultrasonic-assisted electrochemical discharge machining (UA-ECDM) can overcome these hurdles, offering a breakthrough in precision fabrication.
The study, led by Professor Pradeep Dixit and Anurag Shanu from IIT Bombay’s Department of Mechanical Engineering, explains the mechanism behind UA-ECDM’s superior performance. Unlike traditional electrochemical discharge machining (ECDM), which relies on electrical discharges in an electrolyte solution, UA-ECDM introduces ultrasonic vibrations, sound waves beyond human hearing, to enhance debris removal and electrolyte circulation.
Mr. Dixit said, “While earlier studies focused mainly on the experimental results, like machining depth (the depth of the hole or groove), they did not explain the actual mechanism of improvement in machining performance through ultrasonic vibration. By analysing electrolyte flow and debris dynamics, we could explain the fundamental mechanism and the effect of vibration amplitude in improving the debris removal efficiency.”
The team likens the process of unclogging a drain with a plunger. “Imagine a small glass being moved up and down inside a bigger glass filled with water and sugar crystals. As the small glass moves, the water and crystals get displaced and circulated. Similarly, in UA-ECDM, ultrasonic vibration from the tool applies force on the electrolyte at a microscopic scale. This motion removes the debris from the machining gap and circulates fresh electrolyte. The overall sludge removal efficiency was drastically improved after applying the ultrasonic agitation. It has resulted in a 33% higher material removal rate compared to the conventional ECDM approach,” Mr. Dixit explained.
The researchers found holes with an aspect ratio of 2.5 (depth-to-diameter), meaning they were 2.5 times deeper than their width. Compared to conventional ECDM, UA-ECDM produced holes that were 33% deeper and had a 16% higher aspect ratio.
The experimental setup included nine through-holes in a 1.1 mm thick glass substrate using a multi-tip tool. The tool vibrated at 20 kHz (20,000 times per second) with strokes of 5–10 μm, agitating the electrolyte within the microscopic holes. This improved fluid circulation and enhanced debris removal by 50%.
Validation was done using high-speed cameras and energy-dispersive spectroscopy (EDS) to observe the process and analyse elemental composition.
Numerical simulations revealed that at higher amplitudes (around 8–10 μm), nearly all debris particles were cleared within a few vibration cycles, even from deep inside microholes. At lower amplitudes, debris lingered and clogged the gap, while excessive agitation at very high amplitudes risked damaging the tool and workpiece. The study identified an optimal vibration amplitude for maximum efficiency.
“UA-ECDM is useful wherever deep and precise microfeatures such as blind/through-holes/channels, etc, are needed in nonconducting materials like sodalime, borosilicate glass, fused silica, polymer-based composites, and alumina. Specific applications include the embedded integrated passive devices such as inductors, through-glass vias (TGVs)-based 3D packaging of MEMS sensors, microfluidic devices, and lab-on-chip applications,” said Mr. Dixit.
However, the smallest tool tip achievable in the study was 150 μm, due to limitations in wire electric discharge machining (wire-EDM), which constrains further miniaturisation.
The team plans to extend the research to alumina ceramics, which combine electrical insulation with good thermal conductivity but are much harder to machine than glass. As material engineering pushes the boundaries of miniaturisation, “The biggest advances come from the smallest of feats, sometimes with the right amount of vibrations,” Mr. Dixit added.
The findings have been published in the Journal of the Electrochemical Society.
Published – November 17, 2025 03:17 am IST
