Micro-encapsulation

One of the most frequent failures encountered in the encapsulated micro devices is the so-called open circuit, which results from a break of the bonding wire between circuitry. The breakage is primarily due to corrosion. This is initiated by the impurities in epoxy resins, such as halogen, which upon exposure to heat and moisture generate a corrosive acid. 

The general definitions of encapsulation (micro-nano encapsulation) may be applied to any active component X to be encapsulated it is placed in a medium where its mobility and reactivity are reduced, controlled. X is protected inside the microcapsule with a minimal fraction of unprotected X on the surface. 

In the following pages, a study of non-encapsulated micro TLC particles is presented to track the temperature of individual tracers in microfluidic flows using a multivariable calibration approach. 

Segura R, Cierpka C, Rossi M, Joseph S, Bunjes H, Kahler CJ (2012) Digital particle tracking thermography of individual non-encapsulated micro thermo-liquid crystals using a multi-variable calibration approach. Microfluid Nanofluid 14 445-456. doi 10.1007/s 10404-012-1063 -y... 

Lapidot, N. Blanca, M. Rottman, C. Naigertsik, O. Agent-encapsulating micro- and nanoparticles, methods for preparation of same and products contaiiung same. PCT Int. Appl. WO 2004081222, 2004 Chem. Abstr. 2004,141, 296931. 

Figure 8.50 Liquid membrane capsule. The diameter of the capsule is 150 to 1000 /im. The diameter of encapsulated micro droplets is 1 to 5 /im. The encapsulated active phase can contain a catalyst, such as an enzyme the LMC then function as reactors . The reactants diffuse into the catalyst-active phase, and the products diffuse out. The encapsulated phase can also be a reagent. LMC encapsulating a reagent-active phase can be formulated to function as traps. Here the species to be removed diffuses from the solution being treated through encapsulating phase to the reagent-active phase. The reagent converts the material to a non-permeable species which cannot diffuse back through the encapsulating phase and becomes trapped [262].

Other imaging techniques such as magnetic resonance and ultrasound have opened up avenues of tremendous potential for contrast medium enhancement (123). Ultrasound contrast media developments have centered around encapsulated air micro-bubbles. Magnetic resonance contrast agents iavolve metal—ligand complexes and have evolved from ionic to nonionic species, much as radiopaques have. 

Micro-particles can be encapsulated in polymer films, in metal shells or in shells of their... 

The liquid crystal thermographs method has been used for measuring microtube surface temperature with uncertainties of lower than 0.4 K by Lin and Yang (2007). The average outside diameter micro-tubes was 250 pm and 1,260 pm, respectively. The surface was coated with thermochromic liquid crystal (TLC). The diameters of encapsulated TLC were ranging from 5 to 15 pm. The TLC was painted on the tested tubes surface with thickness of approximately 30 pm. 

Insulin (molecular weight 7000) has been formulated in controlled release microbeads and pellets (135,136). A solvent evaporation micro-encapsulation procedure was used to produce microspheres with up to 20% by weight insulin. Solvent-casting techniques were used to prepare pellets. The investigations demonstrated that the PLA... 

Micro encapsulation, which is encapsulation in containments smaller than 1 mm in diameter, is a recently developed new form of encapsulation for PCM. It can currently only be applied to water repelling PCM. Micro encapsulation serves the same purpose as mentioned above for macro encapsulation, but additionally... 

Encapsulations can be divided into two groups (page 219), depending on their size macro and micro encapsulation. 

Micro encapsulated PCM are available from BASF (http //www.basf.com/ corporate/080204 micronal.htm) (Figure 117). 

BASF encapsulates different paraffins with a special process and sells the micro capsules under the brand name Micronal as fluid dispersion or as dried powder (Figure 118). 

Figure 118. Micro encapsulation of paraffin produced by BASF/Germany as fluid dispersion...

Quite similar to direct discharge storages are slurry types (Figure 141). They differ from direct discharge types only because the heat transfer fluid also contains microencapsulated PCM. The micro encapsulated PCM increases the stored heat per volume of heat transfer fluid, which again has to be a fluid... 

Figure 142. Slurry from micro encapsulated PCM (picture BASF AG)...

Since the last oil crisis many attempts have been made to incorporate PCM into building materials like plaster, wood or fiber boards. At the beginning this was done by impregnation, recently micro encapsulation has been preferred as it reliably prevents leakage. The potential of PCM to reduce... 

Figure 194. Integration of PCM into building materials by micro encapsulation (left) and comparison of different wall thicknesses to store a given amount of heat (right)...

Gypsum plaster boards with micro-encapsulated paraffin... 

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