Spark Assisted Chemical Engraving

The research is centred around following activities:

  • Microtools fabrication by WEDG (Wire Electrodischarge Machining) and Chemical etching
  • A novel micromachining technology: Spark Assisted Chemical Engraving (SACE)
  • Study of the physical and chemical effects involved in SACE (electrode effects)

In 1996 at the EPFL started the research on glass machining (Dr. Hans Langen, CTI Project). Since 1996, three mechanical prototypes were designed to use SACE to microstructure glass and other non-conductive materials.

Wire ElectroDischarge Grinding (WEDG)

Small tools with complex shapes can be achieved by WEDG (Wire Electro Discharge Grinding). This technology was proposed in 1985 in Japan by Prof. Masuzawa [1].

WEDG is helpful to machine microtools with a diameter down to 20 microns in hard materials (tungsten carbide..) with a high accuracy. These tools are then used for glass microstructuring with SACE.

[1] Masuzawa, T., Fujino, M., Kobayashi, M., Suzuki, T., Annals of the CIRP, 34, 431 (1985).



Micro Tool Fabrication by Chemical Etching

The demand of ultrathin microprobes has been growing in diverse fields such as atomic force microscopy (AFM) or micromachining.

We use electrochemical etching for producing sharp probes for these purposes. Contrary to conventional fabrication (mechanical for example), no surface damages occur [1].

[1] Lim, Y.M, Kim. S.H., Review of Scientific Instruments, vol. 71, n°5 (2000).


Spark Assisted Chemical Engraving

In 1968, electrical discharges were first used to drill microholes in glass [1]. In the literature, this process is introduced as a combination of Electrochemical Machining (ECM) and Electro Discharge Machining
(EDM) [2].

We propose to call this process SACE (Spark Assisted Chemical Engraving) and to use it to microstructure glass. The goal of this research work is to understand thermal (sparking) and chemical (glass
etching) phenomena induced in the SACE process. Since 1999, two PhD works have been achieved (Fascio and Wüthrich).

[1] Kurafuji, H., Suda, K., Annals of the CIRP, 16, 415 (1968).
[2] Langen, H., Fascio, V. , Wüthrich, R. , and Viquerat, D., in Proceedings of the 3rd EUSPEN Conference, 2, 435, (2002).


Electrode Effects

Electrode effects are known since the work of Fizeau and Foucault from 1844. They are defined according to Vogt [1] as “the phenomenon of an immediate breakdown of the electrolysis without any interference from outside”. Nowadays, intensive studies are conducted because of its technical, ecological and economical implications in the industrial aluminium production.

Many systematic studies were carried out in the second half of last century. More recent results are essentially worked out by Vogt. However a generally explanation of the phenomenon is still missing.

Our approach of the problem is to consider the phenomenon as a stochastic process. The main idea is to consider the onset of the effects as a phase transition. Our model, using percolation theory, predicts the current-voltage characteristics and the conditions of the onset of the electrodes effects as well as the critical voltage, the critical current density and the critical resistance.

[1] H. Vogt: Electrochimica Acta 42 (1997) 2695-2705