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

ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE EPFL

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

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

Micro Nano

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

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) 1095-1108 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) 828-835 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) 1891-1896 A. Cieciwa, R. Wüthrich and Ch. Comninellis: “Electrochemical Characterization of Mechanically Implanted Boron Doped Diamond Electrodes MI-BDD”, Electrochemistry communications 8 (2006) 375-382 R. Wüthrich, E.A. Baranova, H. Bleuler, Ch. Comninellis: “A phenomenological model for macroscopic deactivation of surface processes”, Electrochemistry communications 6 (2004) 1199-1205

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

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

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

Micro machining with SACE

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

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

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 + ®

Improving repeatability 5 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

Two regimes Discharge regime Hydrodynamic regime

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

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

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

Some applications inlet outlet

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) 261-269

Bacterial biosensors 40mm Burkholderia sp. RP037

Nanoparticle fabrication

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

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

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

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