Mems Devices For Biomedical Applications

Micro-Electro-Mechanical Systems technology, commonly known with the acronym MEMS, refers to the fabrication of devices with dimensions on the micrometer scale. The most important characteristic of MEMS is that electronic components are often integrated with micro-mechanical ones, movable or stationary, resulting in very complex miniaturized machine. The low power consumption requirements that derive from their small component size has made these system very precious, as evident from their...

Biomaterials Approach To Gene Delivery

Polymers can also play the role of a gene carrier by serving as a matrix for sustained release instead of a DNA-condensing polycation, or as an excipient in the naked DNA or polyplex formulation. Collagen gel represents the early example of a depot delivering naked DNA 104 . Polymers without charge can encapsulate instead of condense the DNA in nano- and microparticles. Examples are DNA-containing poly(lactide-co-glycolide) (PLGA) nanoparticles fabricated by double-emulsion and solvent...

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FIGURE 2.11. (A) In vitro release of rhodamine from mixtures of 20- m and 65- m diameter PLG microspheres in the ratios 1 4,1 9 and 1 25 w w. Filled symbos are experimental data points for individual microspheres and open symbols are experimental data points for the mixtures. The dotted lines are the weighted average of individual microsphere experimental release data. (B) In vitro release of piroxicam from mixtures of 10- m and 50- m diameter PLG microspheres. with simple microsphere systems....

Application Of Sacrificial Oxide In Devices

Sacrificial oxide has been used in IC fabrication as well in MEMS fabrication. This section reviews the use of sacrificial layer in fabrication of different devices. FIGURE 5.4. a Starting wafer, b the hole patterned before doping, c Boron diffusion through the patterned hole, and back side etching, d Complete fabricated single-crystal silicon membrane 83 . In 1965, Nathanson etal. 2,80,81 used sacrificial layer technique to fabricate resonant gate transistors consistent with silicon integrated...

Sacrificial Oxide Etching

Sacrificial oxide is always etched away, sometimes during the process or mostly at the end of the process. A good etch selectivity is an important requirement for sacrificial oxide etch. The etch rate depends upon many factors, such as doping material, doping concentration, oxide fabrication method and geometry of sacrificial layer. Usually sacrificial oxides are buried layers and only small openings are available for the echants to reach the surface being etched as well as for the etched...

Synthetic Polymeric Gene Carriers

Polyethylenimine PEI is one of the most potent synthetic gene carriers and the most widely studied 23-27 . It can mediate gene transfer in a variety of cells in vitro and tissues in vivo. PEI is available in linear and branched forms. The most commonly studied structure is the 25KD branched PEI, with a combination of primary, secondary, and tertiary amines Figure 9.3 . Every third atom on PEI is a primary amino nitrogen, which can be proto-nated at weakly acidic pH. As a result of this high...

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Chemical structure of branched polyethylenimine PEI . appear to be effective. Although early studies suggest the greater potency of the branched structure 30 , recent studies have compared linear vs. branched PEI and concluded that the linear polymer can be as effective as the branched PEI for transfection in vitro and in vivo 31, 32 . Toxicity is one of the main concerns for PEI, particularly for in vivo delivery. The cytotoxicity is postulated to derive from its ability to...

The Structure And Chemical Reactivity Of Carbon Nanotubes

Carbon Nanotube Graphene Sheet

As can be seen in Figures 6.1A amp B, carbon nanotubes may be viewed as a graphite sheet that is rolled up into a nanoscale tube form single-walled carbon nanotubes, SWCNTs FIGURE 6.1. Schematic representation of A single- multi-walled carbon nanotube formation by rolling up graphene sheet s . B carbon nanotube formation based on a 2D graphene sheet of lattice vectors a1 and a2, the roll-up chiral vector Ch na1 ma2, and the chiral angle 0 between Ch and a1. When the graphene sheet is rolled up...