Responsive barriers

Among the various categories of smart textiles and flexible materials, which include optically, mechanically, chemically, electrically, and thermally activated substances/ stmctures (Tao, 2001), several have shown large opportunities of applications in PPE. This includes wearable electronics, for example, physiological condition, temperature, and humidity sensors, power and data transmitters, and end-of-life indicators, which are the subject of the next chapter of this book. Various types of smart flexible materials have also found their way into PPE, for instance, as responsive barriers, self-decontaminating membranes, thermoregulating layers, and shock-absorbing patches. 

Figure 22.1 Principle of swelling polymer-based responsive barriers, (a) fibrous membrane, (b) porous membrane.

Adjustable breathability is an area where responsive barriers have already found commercial applications. For example, a thermoresponsive breathable membrane using shape memory polyurethane has been developed by Mitsubishi Heavy Industries (SMP Technologies Inc., 2010). It can be laminated onto various types of textiles to provide waterproof, windproof yet breathable clothing. Another strategy based on a temperature-activated breathable monolithic film sandwiched between two layers of spunbond microfibrous polypropylene has been used by Ahlstrom Corp. to develop medical gowns that combine protection against virases with comfort and breathabUity (Rodie, 2005). 

Chen, H., Palmese, G.R., Elabd, Y.A., 2005. Polyester-polyelectrolyte nanocomposite membranes as breathable and responsive barriers. In Proceedings of the 2005 AIChE Annual Meeting and Fall Showcase, October 30—November 4, 2005, Cincinnati, OH, USA, p. 4886. 

Journal of Biomedical Materials Research 57, No.2, Nov.200l,p.l51-64 SELF-ASSEMBLED MOLECULAR STRUCTURES AS ULTRASONICALLY-RESPONSIVE BARRIER MEMBRANES FOR PULSATILE DRUG DELIVERY Kwok C S Mourad P D Crum LA Ratner B D Washington,University... 

Kwok, C.S., Mourad, P.D., Crum, L.A., Ratner, B.D. Self-assembled molecular structures as ultrasonictdly-responsive barrier membranes for pulsatile drug delivery. J. Biomed. Mater. Res. 57, 151-164 (2001)... 

Delay an attack for a sufficient period of time to allow appropriate response through onsite security response, barriers and barricades, hardened targets, and well-coordinated response planning. 

The key quantity in barrier crossing processes in tiiis respect is the barrier curvature Mg which sets the time window for possible influences of the dynamic solvent response. A sharp barrier entails short barrier passage times during which the memory of the solvent environment may be partially maintained. This non-Markov situation may be expressed by a generalized Langevin equation including a time-dependent friction kernel y(t) [ ]... 

Phosphatidylcholine is an important component of cell membranes but cell mem branes are more than simply lipid bilayers Although their composition varies with their source a typical membrane contains about equal amounts of lipid and protein and the amount of cholesterol m the lipid fraction can approximate that of phosphatidylcholine The lipid fraction is responsible for the structure of the membrane Phosphatidyl choline provides the bilayer that is the barrier between what is inside the cell and what IS outside Cholesterol intermingles with the phosphatidylcholine to confer an extra measure of rigidity to the membrane... 

A key feature of encapsulation processes (Figs. 4a and 5) is that the reagents for the interfacial polymerisation reaction responsible for shell formation are present in two mutually immiscible Hquids. They must diffuse to the interface in order to react. Once reaction is initiated, the capsule shell that forms becomes a barrier to diffusion and ultimately begins to limit the rate of the interfacial polymerisation reaction. This, in turn, influences morphology and uniformity of thickness of the capsule shell. Kinetic analyses of the process have been pubHshed (12). A drawback to the technology for some apphcations is that aggressive or highly reactive molecules must be dissolved in the core material in order to produce microcapsules. Such molecules can react with sensitive core materials. 

Soap as used in personal cleansing products has a long safe history of use. Modem soaps have been specifically formulated to be compatible with skin and to be used on a daily basis with minimal side effects. Excessive use of soap for skin cleansing can dismpt the natural barrier function of skin through the removal of skin oils and dismption of the Hpid bdayer in skin. This can result in imperfect desquamation or a dry appearance to skin and cause an irritation response or erythema, ie, reddening of the skin. Neither of these is a permanent response and the eHcitation of this type of skin reaction depends on the individual s skin type, the product formulation, and the frequency of use. 

Skin. The skin s unique molecular transport and barrier properties pose a challenge for transdermal dmg dehvery. Diffusion of dmgs through the stratum corneum, the outer layer primarily responsible for the skin s limited permeabUity, varies by dmg, by skin site, and among individuals. Until recently, virtuaUy aU dmgs appHed to skin were topical treatments. 

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