Freestanding membrane

Anodically grown aluminum oxide (AI2O3) has also been used extensively as a template [3,32-37]. When grown on high-purity aluminum, this material has a hexagonal pattern of cylindrical pores, which extend through the thickness of the alumina (Fig. 1C and ID). These microporous alumina films can be removed from the substrate A1 metal and collected as a freestanding membrane [37,38]. 

Hsu Y-J, Chang Y-H, Chai Y-L, and Chen G-J, The influence of residual stress and membrane thickness on the performance of Fe—Ni—Cr = Invar bimetal freestanding membrane for microdevices. Sens Actuators A 2002 101 160. 

Other authors [7] consider the properties of the fuel cell instead of the freestanding membrane to define a MEA-selectivity parameter, a, as the reciprocal of the high frequency resistance times the alcohol crossover limiting current. In this... 

Deslouis, C., et al. 1995. Comparison of the AC impedance of conducting polymer films studied as electrode-supported and freestanding membranes. J Electrochem Soc 142 (6) 1902. 

BLMs may be prepared as supported or freestanding membranes. Membranes deposited on solid supports are easier to prepare and more stable and have been studied extensively [502-508] however, the use of an unsupported bUayer membrane separating two solutions is more important [509-517]. The resistances of the membranes are large and the capacitances are on the order of approximately 1 p F cm". ... 

The impedance of freestanding membranes may be studied using the system displayed in Fig. 12.5. It uses a homemade differential amplifier. Similar possibilities occur with the use of two potentiostats, allowing for the grounding of the working electrodes (e.g., from Bank Elektronik [518]) or using a SolartrOTi dielectric interface [519, 520]. 

Most commercial UF and NF membranes and many MF membranes are made by the phase-inversion process, where a polymer is dissolved in an appropriate solvent along with appropriate pore-forming chemical agents. The polymer solution is cast into a film, either on a backing or freestanding, and then the film is immersed in a non-solvent solution that causes precipitation of the polymer. Such membranes are Polyamides, such as nylon, polyethersulfon (PESU), or... 

Entrapment methods of immobilization of bioreceptors utilized the lattice structure of particular base material. They include such methods as entrapment behind the membrane, covering the active surface of biosensors, entrapment within a self-assembled monolayers on the biosensor surface, as well as on freestanding or supported bilayer lipid membranes, and also entrapment within a polymeric matrix membranes, or within bulk material of sensor. All these mentioned methods are widely employed in design of biosensors. The essential condition of success of these methods of immobilization is preservation of sufficient mobility of substrate or products of biochemical reaction, involved in sensing mechanism, as matrix may act as a barrier to mass transfer with significant implications for... 

The manufacturing processes represent the link between the reliability issues of the microstructure on one hand and those of assembly and packaging on the other. The process flow must take into account, for example, the impact of the applied temperature range, pressure, and media on the sensor structure, which at the time of packaging is already completed. Dicing of sensor structures that include delicate elements, such as freestanding cantilevers or thin membranes, is usually very critical and requires some kind of protection which can be effectively provided by zero-level packaging on the wafer scale. 

Xu H, Goedel WA (2002) Polymer-silica hybrid monolayers as precursors for ultrathin freestanding porous membranes. Langmuir 18(6) 2363-2367... 

The novel feature of our approach is to prepare freestanding, thin membranes by vacuum deposition on to a suitable temporary substrate that can easily and cleanly be removed. Important requirements for the substrate material are that it be very smooth and free of contaminants, pinholes and surface defects. The materials should also have decent thermal stability and be inexpensive (relative to the membrane), reusable and/or recyclable. Based on these requirements, two initial approaches were envisioned (1) deposition of the membrane onto a polymeric substrate, which can be subsequently chemically dissolved or (2) deposition onto a rigid substrate with and without pre-treatment with a thin release coating that may be water soluble. 

Experimental deiection of the formation of ion channels is best achieved using the bilayer clamp technique. In this experiment, a freestanding bilayer membrane is interposed in a small orifice separating two pools of aqueous... 

The nanotubes can be left embedded within the pores of the template to yield a freestanding nanotube-containing membrane. We have shown that the nanotubes can act as conduits for highly selective transport of molecules and ions between solutions present on either side of the membrane. For... 

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