6 “Magic Tricks” of Micro—nano Manufacture Technology

Written by Ma Jiang

The world is marching into Micro-nano era. With micro-nano manufacture technology， elements can be made from complex and massive scale into micro-nano one while maintaining its original function. Micro-nano manufacture is becoming an reality nowadays， techniques and materials of which has always been the cornerstone of the construction of buildings of nanotechnology. Lets feel 6 “Magic Tricks” of it now！

Mechanical micro-machining

Among micro-nano manufacture， mechanical micro-machining is the most convenient micro-molding technique which is the closest to traditional materials processing methods. It generally includes turning， drilling， grinding， etc. To improve the accuracy and degree of automation， modern mechanical micro machining is usually equipped with a computer control system such as computer-numerical-control （CNC）， and through the diamond tool making microstructure of high quality on the surface of various materials.

Mechanical micro-machining process method is simple and the process is easy， but selective to the process materials， often using in materials like copper alloy， nickel alloy， etc. Most commonly used metal materials like steel can not be made through mechanical micro-machining methods， because the carbon in the steel will react with the diamond tools.

Additionally， the minimum size of the micro-mechanical structures made by micro-machining method is very limited， only about 200 microns， which limits this method in application areas of devices of smaller micro structure.

Laser micromachining

Laser technology is known as one of the four important inventions of the 20th century. With small electronics and microelectronics components surging in demand， laser micromachining field of laser development has become one of the fastest in industrial applications.

With high energy density， good direction， adjustable spot size， laser processing uses these features to change its light energy into heat in order to erosion materials. The range of its target materials is very wide， covering almost all of the metal and non-metallic materials. Comparing to mechanical micro-machining， it is a non-contact process， where there is no tool wear or tear and no obvious mechanical force， hence it will not generate the machining distortion.

Currently laser micromachining technology is still in its infancy. With the development of laser technology （such as improved light source， energy density， etc.）， in the future， this "artifact" will surely flex its muscles in the micro-nano manufacturing.

electric discharge micro-machining

Electric discharge machining，EDM， is a special micro-nano manufacturing and processing method using galvanic action between immersed poles during pulse charge or discharge to conduct material erosion.

EDM micro-processing technology will not be affected by hardness of materials， and by adjusting the electrical parameters， it can easily achieve switches among rough， semi-fine， fine， and super accurate manufacturing， hence it is also applied to micromachining fields. At present， this biggest drawback of this method is the low processing efficiency.

Explosion+ Etching

Currently the most commonly used micro-nano manufacturing technique is LIGA （German acronym， Lithographie， Galanoformung and Abformung， namely lithography， electroforming and injection）.

Due to the capability of processing materials of small size， high precision， as well as being suitable for processing semiconductor materials， this technology is widely used in the semiconductor industry， whose most basic core technology is lithography， namely exposure and etching process.

With the development of LIGA technology， people have developed a variety of different exposure， etching process to meet different size precision， productivity and other needs. X-ray exposure methods include ultraviolet， laser， electron beam exposure， etc. Concerning etching， there are two kinds， wet and dry. Wet etching uses a chemical characteristic of the material， dissolving it away in a particular solution. On one hand， it has high selectivity， uniformity， and less damage to the silicon wafer， etc.， while on the other hand， it also has week anti-aliasing ability， horizontal tendency and over-corrosion， etc.

LIGA technology after years of development has already been quite mature， but the basic principles of technique determine the defect that it is bound to exist， such as the complexity of the process， high environmental requirements for preparation （such as the need clean rooms， etc.）， higher equipment investment as well as high production costs.

Electroforming micromachining

Electroforming micromachining is a special manufacturing method using metal electrowinning principle to clone some complex or special shape of workpieces. By depositing metal fabrication techniques on a metal layer， it processes microstructures.

Instep mold in Electroforming micromachining commonly uses stainless steel， aluminum， titanium， epoxy resin， glass and other materials. After a simple treatment on surface， put the instep mold inside the cell， using electrolytic deposition principle to form metals on the instep one. When the layer reaches the desired thickness， apply mechanical or chemical methods to separate the deposited metal and instep mold.

With high accuracy and repeatability， this method is of wide application， able to be used to manufacture sophisticated， complex inner profile parts. But due to the limitation of technical principles， once unstable in quality， the electroforming layer will prone to pitting， pinholes， coarse grains， too much stress and other defects， resulting Deposits in physical properties and mechanical performance degradation. If severe enough， it will lead to the uselessness of all the elements.

In addition， the cast layer uniformity is poor and the mold on complex surface is very uneven due to electric field distribution， so that the current density in the entire surface of the mold is inconsistent， which could easily lead to significant differences between the sediment thickness throughout， thus affecting the performance of various parts. As time passes by， this uneven deposition will increase. Its long processing time and limited kinds of casting material also form its disadvantage.

Model Processing

Model processing method is to copy corresponding micro-nano structures via the use of micro-nano sized molds. This method is mainly applied to thermoplastic materials， such as polymer plastic， metal and glass.

First， heat the thermoplastic material and the micro-model one to a certain temperature； after the thermoplastic material is soften due to lower viscosity， exert a certain stress to make it fill and float in the micro-flow model； finally micro-nano structures on micro model will be successfully transferred to the surface of the thermoplastic material.

Model processing technology includes nanoimprinting， plastic molding and molding techniques. Nanoimprinting imprints stamps containing micro-nano-imprint patterns onto a softened organic polymer layer. Nano-stamp can also be made through other micro-nano processing methods. This technology can lower cost， make mass reproduction of nanometer graphics. There are a variety of derivative nanoimprint techniques as well， such as using exposion to imprint nano graphics.

Molding technology is conventional plastic molding technology， with the molded structure size in microns or more， which is more for microfluidic biochip production. Molding technology is also a low-cost micro-processing technology. Molding technology includes plastic and metal molding techniques. Whether imprinting or molding are extension of traditional processing techniques to micro-nano field， which is of fast forming speed and also suitable for mass production.

In recent years， the research and application of micro-nanotechnology is being filled with new boom. Considering from the scientific point of view， the existed processing technology has been able to meet the production and research of nanoscale devices， but these "artifacts" after all， are difficult to be massively produced. For industrialization of micro-nano research results， in the future we still need to develop micro processing technologies of high productivity and low cost.

It can be predicted that the next 50 years will be the booming era of micro-nano technology！ The potential of micro-nano processing technology is magnificent and new processing technologies will continue to emerge. They will help mankind to develop more new micro-nano devices and systems， hence stepping further into the new world of miniaturization.