Microtools

For the last ten years or so, a handful of groups world-wide have been working to develop microtools for cell handling. The aim is to develop a series of basic elements which can be juxtaposed and connected to build useful devices. This work draws heavily on techniques pioneered for semiconductor manufacture. The results are promising and the number of groups is increasing as the result of industrial interest. 

Tools for microfabrication have also been prepared based on the unique characteristics of carbon nanotubes. In the microtool shown in Fig. 5.23, two carbon nanotubes are fixed on gold electrodes that are deposited either side... 

Jan, G. Lothar, S. Heinz, W. Chemical vapour deposition diamond coated microtools for grinding, milling, and drilling. Diamond Relat. Mater. 2000, 9, 921-924. 

Fig. 14 Flow switch using magnetically driven microtool [49]. (a) Operation of magnetically driven microtool.

Silicon carbide fibers wifh diameters between 100 and 500 pm and alumina hollow fibers with a wall thickness of 30 pm were successfully produced for microtool applications like heat exchanger tubes, refractory tools, thermocouple protection tubes and electric heating elements. Examples of these two fibers are shown in Fig. 5. The strength of the SiC fibers was shown to be as high as for SiC bulk material 800 MPa (tensile test with a free clamping length of 50 mm), which is sufficient for microtool applications. 

Cle05] Clemens FJ, Wallquist V, Buchser W, Wegmann M, Graule T (2005) Silicon Carbide Fiber-Shaped Microtools by Extrusion and Sinterning SIC with and without Carbon Powder Sinteming Additive. Ceram Int - submitted... 

The general tool for system analysis - case/4/0, in its current 5.0 yersion, by microTOOL, Germany, has been used for the Requirement Management System in ihe project I C System Refurbishment for NPP Dukoyany. 

Generally, initial investment of process design and microtool fabrication is low. Running cost and tooling costs are also low. 

Since hydrogen gas evolution is the only reaction at the cathode microtool, the shape of that microtool remains unaltered during the electrolysis therefore it can be reused multiple times. 

This process needs careful handling of microtools with in situ fabrication. 

In case of EMM, the normal value of applied pulsed potential across the electrodes, which maintain a narrow gap, is much less and current is in the order of microampere. Pulse frequency is very large, i.e., in the order of megahertz, which minimizes the machining cycle time. During this very small cycle time as well as due to the stagnant nature of electrolyte, it is difficult to overcome the charge transfer resistance, which may lead to deposition of metal ions or sludges on the surface of the microtool or workpiece. 

In micro-ECM, the lEG is very narrow, which may cause deposition of metal ions as well as sludges on the microtool. Acidic electrolyte is suitable for micro-ECM due to its ability to dissolve metal hydroxide. However, it may cause deposition of metal ions and metal hydroxide on the microtool, which leads to poor machining. To overcome this, frequent replenishment of acidic electrolyte as well as frequent reversing of polarity may be considered as some of the effective approaches. 

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