Micro-optical devices

Microlenses are used extensively in cell phone cameras (18). 

Micro inkjet printing is a direct patterning method for the manufacture of micro-optical systems. Inks for these patterning techniques have been described (19). This is an epoxy resin- and a sol-gel-based material. 

Epoxy-based compositions are based on a solid epoxy resin, a photoadd generator and a solvent. The viscosity of the inks can be tuned either by adding solvents or reactive diluents. A dynamic viscosity of 20-30 mPa s is desirable. As a sol-gel based material, an organically modified ceramic was used (19). 

Multiscale microlens arrays can be directly fabricated on a hydrophobic flat surface by a simple inkjet printing technique (20). Inorganic/organic hybrid precursor polymers based on silicones are used. These structures are modified with organic structures that can be eventually crosslinked (21). 

An acrylate-based photocurable ink is used. The surface of the substrate to be printed must be pretreated in several steps, including oxygen plasma treatment, surface hydroxylation, and an anti-adhesion treatment. Onto this surface, the ink can be printed by the drop-on-demand method. The angle of the lenses depends on the method of pretreatment (20). 

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A fiber-optic electrode was fabricated for the simultaneous generation and transmission of electrochemical luminescence by preparing a transparent electrode on the optical and surface of a fiber-optic. The opto-electrochemical properties of the micro-optical device were characterized in solutions containing the compounds required for luminol luminescence. The validity of sensitive measurement of electrochemiluminescence to be employed in a homogeneous immunoassay was evaluated by using potential step excitation of luminol in the presence and in the absence of hydrogen peroxide. 

Electrochemically etched porous silicon can exhibit pronounced optical anisotropy even though bulk silicon is basically optically isotropic. The origin of this effect, the most significant parameters, and potential applications in sensing and micro-optic devices are reviewed. 

With the development of single-mode waveguides, it is possible to fabricate more complicated micro-optical devices such as X [85], Y [86] couplers... 

One major problem with femtosecond laser processed micro-optical devices is the large power dissipation due to Rayleigh scatterings fi om the particle-like fine structures, which is difficult to control in the fabrication process because of an intense laser-matter interaction at the femtosecond time scale. Suitable post-irradiation treatments should be found to improve performance of devices [31]. 

Polymers have come a long way from parkesine, celluloid and bakelite they have become functional as well as structural materials. Indeed, they have become both at the same time one novel use for polymers depends upon precision micro-embossing of polymers, with precise pressure and temperature control, for replicating electronic chips containing microchannels for capillary electrophoresis and for microfluidics devices or micro-optical components. 

R 18] [A 1] Each module is equipped with a heater (H3-H8) and a fluidic cooling (C03-C06). Temperature sensors integrated in the modules deliver the sensor signals for the heater control. Fluidic data such as flow and pressure are measured integrally outside the micro structured devices by laboratory-made flow sensors manufactured by silicon machining. The micro structured pressure sensor can tolerate up to 10 bar at 200 °C with a small dead volume of only 0.5 pi. The micro structured mass flow sensor relies on the Coriolis principle and is positioned behind the pumps in Figure 4.59 (FIC). For more detailed information about the product quality it was recommended to use optical flow cells inline with the chemical process combined with an NIR analytic or a Raman spectrometer. 

A miniaturized Fourier transform spectrometer for near-infrared measurements (FTIR, 2500-8330 nm) was developed at the Forschungszentrum Karlsruhe [120], Near-infrared measurements give information, for example, about the oil, water and protein content of liquids or solids. The dimensions of the detector chip are 11.5 x 9.4 mm, the device is essentially a miniaturized Michelson interferometer and it consists of a micro optical bench with beamsplitter, ball lenses, mirrors and the detector chip. The light beam is coupled in via a glass-fiber and an electromagnetic actuator. The signal is derived from the signal response of the detector by Fourier transformation. 

Microfabrication is growing in importance in a wide range of areas outside of microelectronics, including MEMS, microreactors, micro analytical systems and optical devices. Photolithography will continue as the dominant technology in the area of microelectronics for the foreseeable future. Photolithography has, however, a number of limitations for certain types of applications, as discussed in Sect. 3.1. 

Horiuchi, T., Ueno, Y., Niwa, O., Micro-fluidic device for detection and identification of aromatic VOCs by optical method. Micro Total Analysis Systems, Proceedings 5th pTAS1 Symposium, Monterey, CA, Oct. 21-25, 2001, 527-528. 

Since optical devices can only detect those particles which fall within their viewing volume, a capability to concentrate hazardous biological particles into such a volume should greatly enhance the detection sensitivity of such devices. This work aims at the concentration of 1-micron-size micro-organisms from about 100 ml of liquid, whether drawn from a bio-aerosol collector or from an environmental source, into a volume of 1 to 2 ml. Extension of the same approach to the concentration of smaller (0.1-micron-size) viral particles is also under way. 

M. Schluter, M. Hoffmann, N. Rabiger, Characterization of micro fluidic devices by optical measurements, in ASME (Ed.), Proceedings of the 5th International Conference on Nanochannels, Microchannels, and Minichannels (ICNMM 2007), American Society of Mechanical Engineers, New York, 2007, p. 1097. 

Microelectromechanical systems (MEMS) combine the electronics of microchips with micromechanical features and microfluidics to create unique devices. The multitude of MEMS applications continues to grow including many types of accelerometers, radio frequency (RF) devices, variable capacitors, strain and pressure sensors, deformable micromirrors for image projection systems, vibrating micro-membranes for acoustic devices, ultrasound probes, micro-optical electromechanical systems (MOEMS) and MEMS gyroscopes, to name a few. 

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