1. Using Electrochemical Discharges for Micro- and Nano-system fabrication
Rolf Wüthrich
Department of Mechanical and Industrial Engineering
Concordia University

2. ÉCOLE POLYTECHNIQUE
FÉDÉRALE DE LAUSANNE
EPFL

3. Research interersts Fundaments of electrochemical discharges (ECD)
Micro-system fabrication using ECD
Nano-system fabrication using ECD
Keywords: Electrochemical discharges, micro-systems, nano-particles, percolation theory, electrochemical reaction dynamics

4. What are Electrochemical discharges ?DC
Anode (+)
(large electrode)
Cathode (-)
Voltage supply
Electrolyte

5. Micro
Nano

6. Current projects
Physical and chemical characterization of SACE drilling (P. Maillard, Master Student EPFL)
Nano-machining using an electrolytical STM (A. Lal, PhD; collaboration with Prof. H. Bleuler )
Dynamics of electrochemical 3D interfaces (E. Calderon, PhD; collaboration with Prof. Ch. Comninellis)
Effect of tool geometry on SACE machining of various materials (R. Benjji, Master; collaboration with Dr. M. Packirisamy

7. Five Most significant publications
R. Wüthrich, V. Fascio: “Machining of non-conducting materials using electrochemical discharge phenomenon – An overview”, International Journal of Machine Tools and Manufacture 45 (2005)
R. Wüthrich, L.A. Hof: “The gas film in Spark Assisted Chemical Engraving (SACE) - A key element for micro-machining applications” International journal of Machine Tools and Manufacture 46 (2006)
R. Wüthrich, U. Spaelter, Y. Wu, H. Bleuler: “A systematic characterization method for gravity feed micro-hole drilling in glass with Spark Assisted Chemical Engraving (SACE)”, Journal of Micromechanics and Microengineering 16 (2006)
A. Cieciwa, R. Wüthrich and Ch. Comninellis: “Electrochemical Characterization of Mechanically Implanted Boron Doped Diamond Electrodes MI-BDD”, Electrochemistry communications 8 (2006)
R. Wüthrich, E.A. Baranova, H. Bleuler, Ch. Comninellis: “A phenomenological model for macroscopic deactivation of surface processes”, Electrochemistry communications 6 (2004)

8. Fundaments of ECD å p sn R A t U - × D + = 1 ) ( a x c s B n d crit
max a x

9. Objectives
Improve fundamental understanding of ECD with the goal to apply it to
Micro-system fabrication
Nano-system fabrication

10. Some results
Formation of ECD described as a generalized phase transition (percolation theory)
Quantitative model for the critical parameters
Insights on the gas film formation dynamics

11. Micro machining with SACE

12. Mechanical Prototype for machining by SACE
A typical SACE machine
Micro-tool fabrication by Wire Electrodischarge Grinding (WEDG)
200mm
SACE applications : Holes drilling, micro-reactor fabrication
50mm
2mm
Mechanical Prototype for machining by SACE

13. Key values Typical pattern sizes: 100-1000mm
Materials: glass, quartz, various plastic materials, some ceramics
Very good surface qualities
High aspect-ratio (up to 10)
Mean-speed: 15 – 100 mm/s
Resolution: 20mm

14. Model of material removal
Gas film
Electrolyte
Electrode (-)
Work piece
T~100°C
Molten NaOH and Glass
T~TG O H
SiO Na
2NaOH 2 3 +

15. Improving repeatability5 10 15 20 25 30
0.6 1
1.6
U [V]
I [A]
NaOH30%wt
200mm
20mm 5 10 15 20 25 30
0.5
0.9
U [V]
I [A]
NaOH30%wt +
soap
200mm
5mm

16. Two regimes
Discharge regime
Hydrodynamic regime

17. Micro-hole quality
R. Wüthrich, B. Despont, P. Maillard, H. Bleuler, International journal of Machine Tools and Manufacture, SUBMITTED

18. Material removal rate
Estimation of MRR:
Glass b=200mm

19. Improving by tool vibration
R. Wüthrich, B. Despont, P. Maillard, H. Bleuler, Journal of Micromechanics and Microengineering, SUBMITTED

20. Some applications
inlet
outlet

21. Multi-layer microfluidic glass chips for microanalytical applications
A. Daridon, V. Fascio, J. Lichtenberg, R. Wüthrich, H. Langen, E. Verpoorte, N.F. De Rooij, Fresenius J. Anal. Chem. 371 (2001)

22. Bacterial biosensors
40mm
Burkholderia sp. RP037

23. Nanoparticle fabrication

24. The principle
Electrode (-) M+ e- e- M+ e- e- M+ M+
H2PtCl6 + HClO4

25. Various composition / alloys
Goal: Pt-Ru nanoparticles for fuel-cells
EDX analysis

26. Controlling the size
Basic idea: Size given my mean residence time of M+ in the reaction zone
Solution:
Control flow of electrolyte around electrode
Goal:
Control size in the range from 10nm to 100nm

27. Conclusion Electrochemical discharges can be used to:
Micro-machining of glass and other materials
Excellent surface qualities
Sizes from 100mm to several mm
High aspect-ratio machining possible
Fabricate nano-particles
Sizes from 10nm to 100nm
Formation of alloys possible