Materials and Manufacturing
Materials and manufacturing deal with the application of knowledge relating to composition, structure and processing of materials to their properties and applications.
In the last few years there was significant increase in the development of composite materials with excellent properties. Composite materials are engineered materials which are made from two or more constituent materials with significantly different physical or chemical properties. Nanotechnology has emerged as a key technology used in fabrication of composite materials.
Though “top-down” fabrication methods are still used, nanotechnology has empowered a “bottom-up” approach to modify the material properties at nanoscale level.
A classic (“top down”) method for nanofabrication is electron beam lithography (EBL). In EBL a beam of electrons is scanning across a surface covered with a film (called the resist). The beam removes selectively either exposed or non-exposed regions of the resist. The result is very small structures in the resist that can be transferred into another material, for example for the creation of very small electronic devices. EBL can produce structures smaller than 10 nm which can be used in applications such as solar cells and other semiconductor and optoelectronics devices.
Another example of a method for the fabrication of nanopatterns is called nano-imprint lithography. This is a tool in which a master mask is made using a serial technique like EBL then is stamped into soft polymer like polydimethylsiloxane (PDMS). This method has achieved resolutions of 10 nm and can be used to make microchannels and other biomedical devices.
An interesting method of forming a periodic nanostructure from the bottom up is called self-assembly. Self-assembly occurs when certain material are energetically attracted to one another and come together to form a repeating pattern on the molecular level. This technique has been likened to a jigsaw puzzle shaken in a box, and when the box is opened, the puzzle has assembled itself.
A good example of manufacturing a specific nanostructure is carbon nanotubes (CNTs). CNTs have excellent mechanical, electrical and optical properties. Depending on their use, CNTs can be manufactured to have high tensile strength and high electrical conduction.
They have been recently used to reinforce and impart mechanical strength to a variety of polymer composites which are used as body armor, transmission line cables and textiles. Ballistic electron transport properties make CNTs an attractive material for device interconnections in computers and the liquid crystal display (LCD) industry.
Carbon nanotubes were first synthesized by the Japanese physicist Sumio Iijima when studying the deposits left on the cathode during the arc-evaporation synthesis of fullerenes (a type of carbon molecules). Since this discovery, carbon nanotubes have been synthesized by controlling the conditions of the arc-evaporation process. Aside from this synthesis method, carbon nanotubes can be fabricated using techniques such as sputtering, chemical vapor deposition, and plasma enhanced chemical vapor deposition.
Ceramics are another interesting nanomaterial that belongs to a class of materials that are processed in a high temperature environment.
Advances in ceramic manufacturing technology have led to its application in building materials such as bricks and stone blocks. Its excellent thermal and electrical properties make it a viable material for applications such as spark plugs and high thermal resistant tiles in space shuttles. Glass- ceramic composites are also used in optical equipment. Materials and manufacturing technology looks into various aspects of material science to develop state of the art applications with low manufacturing costs and high durability.