Microfabrication techniques photolithographic technique

Planar waveguides are also used for photometric transducers. Recently, there have been applications of photolithographic methods to create miniaturized waveguides, or other microfabrication techniques to produce thin films of organic materials for optical waveguides. For example, Hanken and Corn... 

Microfabrication and micromachining techniques have also been used in the manufacture of electrochemical sensors. This includes po and pco sensors. Zhou et al [9] describe an amperometric CO2 sensor using microfabricated microelectrodes. In this development, silicon-based microfabrication techniques are used, including photolithographic reduction, chemical etching, and thin-film metallization. In Zhou s study, the working electrodes are in the shape of a microdisk, 10 pm in diameter, and are connected in parallel. In recent years, silicon-based microfabrication techniques have been applied to the development of microelectrochemical sensors for blood gases, i.e. P02. Pcoj and pH measurements. 

SECM has been particularly promising for microfabrication and detection of biological molecules, mainly due to the mild patterning conditions and various modes of operation (see also Section 12.4.6.2.3). In contrast, conventional photolithographic techniques are usually limited due to the photoresists, organic solvents, and strong acids and bases that are necessary and are harmful to biological molecules. 

Photolithography is the most diffused technique for the fabrication of regular arrays of microelectrodes. Photolithography is a microfabrication technique which is based on the selective removal of parts of thin films (photoresist) exposed to UV light. This procedure allows one to obtain regular arrays of micro electrodes with high spatial resolution, nonetheless this technique requires special and expensive equipments besides, the photolithographic process requires access to a clean room. 

As the analytical, synthetic, and physical characterization techniques of the chemical sciences have advanced, the scale of material control moves to smaller sizes. Nanoscience is the examination of objects—particles, liquid droplets, crystals, fibers—with sizes that are larger than molecules but smaller than structures commonly prepared by photolithographic microfabrication. The definition of nanomaterials is neither sharp nor easy, nor need it be. Single molecules can be considered components of nanosystems (and are considered as such in fields such as molecular electronics and molecular motors). So can objects that have dimensions of >100 nm, even though such objects can be fabricated—albeit with substantial technical difficulty—by photolithography. We will define (somewhat arbitrarily) nanoscience as the study of the preparation, characterization, and use of substances having dimensions in the range of 1 to 100 nm. Many types of chemical systems, such as self-assembled monolayers (with only one dimension small) or carbon nanotubes (buckytubes) (with two dimensions small), are considered nanosystems. 

Microfabrication by SPMs is in part motivated by their potential to beat the diffraction limitations of optical methods for electronics applications. The spatial resolution of SPM is limited only by the tip size and STM has been used to manipulate individual atoms. However, the typical tip size in SFCM is ca. 1 pm and therefore a significant improvement over photolithographic resolution is not routinely obtained. Further, SPMs are rather slow since they are limited by the speed of the tip and this is especially so for SECM. Instead, SECM microfabrication is often more useful as a technique for patterning surfaces with chemical or biochemical functionality and fabricating microscopic structures with particular chemical properties. 

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