Microparticle generation techniques

Survey of Polymer Powder and Microparticle Generation Techniques... 

Particles generation from gas saturated solutions (PGSS) has also been proposed. In this case the product to be micronized is liquefied by heating and addition of SC-COj then, the gas-liquid solution is sprayed in a low-pressure vessel, thus obtaining microparticles. This technique has been successfully used to process some polymers, but has limited applicability in the case of thermolabile compounds that can decompose during heating. - ... 

Recently, the LbL technique has been extended from conventional nonporous substrates to macroporous substrates, such as 3DOM materials [58,59], macroporous membranes [60-63], and porous calcium carbonate microparticles [64,65], to prepare porous PE-based materials. LbL-assembly of polyelectrolytes can also be performed on the surface of MS particles preloaded with enzymes [66,67] or small molecule drugs [68], and, under appropriate solution conditions, within the pores of MS particles to generate polymer-based nanoporous spheres following removal of the silica template [69]. 

Some preparation methods specific to the formation of nanoparticle suspensions are provided in References [20,62,63]. Many such methods are simply conventional colloidal suspension preparation methods that have been extended to produce smaller particle sizes, but others involve novel approaches. Some ofthese involve making nanoemulsions as a first step. For example, membrane, microfluidic and nanofluidic devices have been used to make nanoscale emulsions of all kinds, as already noted earlier, and the emulsion droplets so generated can be used in turn to make sohd microparticles and nanoparticles. If the nanoparticles are intended to encapsulate other materials, then a double emulsification technique can be used, at elevated temperature, to prepare a multiple emulsion (i.e. 

The most prominent technique among these is based on soft lithography [97]. This set of methods allows the generation of micropattemed polymer surfaces or microparticles of different shapes. Each method has certain limits such as scale and aspect ratio (cf. Table 3.5) that will be discussed in detail. Initially, two methods from soft lithography micropatterning and micromolding will be described, originally developed by Whitesides and coworkers. The technique relies on an elastomeric soft material that is either used as a stamp or as a mold in order to pattern surfaces 2D with a monolayer or 3D with a microstmcture (Fig. 3.65). In the first case, one can obtain a fine monolayer pattern (-lOOnrn) but no aspect ratio can be obtained. Nevertheless, by... 

Velocimetry is the measurement of fluid velocity. In the context of microfluidics and nanofluidics, velocimetry involves the determination of the velocity field in small-scale internal flows. Most commonly, velocimetry involves optical tracking of a fluid marker. In such cases, the terms flow visualization and velocimetry are used interchangeably. A variety of velocimetry methods have been developed for small-scale flows. Visualization-based methods can be divided into particle-based techniques such as microparticle image velocimetry and scalar-based techniques such as molecular tagging. Nonvisualization-based velocimetry methods have also been developed such as electrochemical velocimetry, where fluid velocity is determined via generation of a redox species. 

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