Smart films

In situ IR spectroscopy is interesting for a broad range of technological applications, e.g., in (i) biomedicine and biochemistry, (ii) electrochemistry, (iii) catalyses, and (iv) microfluidic devices. In particular, it is relevant for the design of functional templates for drug release [5], studies of smart films and surfaces [11], characterization... 

Smart Film Controls Plant Growth , British Plastics and Rubber, p. 27, Jan. 2001 D. Graham-Rowe, New Scientist 168 (2259), p. 24,7th Oct.2000 M. Achon, European Plastics News 29 (4), 20-21 (2002)... 

Sneller, J.A. (1986) Smart films give a big lift to controlled atmosphere packaging. Mod. Plast. Internat. 16(9), 58-59. 

Materials that typify thermoresponsive behavior are polyethylene—poly (ethylene glycol) copolymers that are used to functionalize the surfaces of polyethylene films (smart surfaces) (20). When the copolymer is immersed in water, the poly(ethylene glycol) functionaUties at the surfaces have solvation behavior similar to poly(ethylene glycol) itself. The abiUty to design a smart surface in these cases is based on the observed behavior of inverse temperature-dependent solubiUty of poly(alkene oxide)s in water. The behavior is used to produce surface-modified polymers that reversibly change their hydrophilicity and solvation with changes in temperatures. Similar behaviors have been observed as a function of changes in pH (21—24). 

An interesting material with both electro- and therm ochromism behavior, Li VO2 was evaluated for a "smart window" appHcation (25). Films of Li V02 were prepared by reactive sputtering and annealing an electrolyte of LiClO and propylene carbonate. 

For smart cards, micro-robots and small precision instruments, thin laminated micro-cells are being developed. Some of these developmental thin-film devices—using an electrolyte of lithium, a copper cathode, and lithium again for the electrode—can charge and discharge up to 3 volts, and can be expected to tolerate up to 1,000 charge-and-discharge cycles. 

In this Section, we describe two complex deformations due to electric field-associated swellings. One is the bending of a hybrid gel consisting of a PVA-PAA gel rod and a PVA film in dc fields. The hybrid gel has been used to fabricate a smart gel finger. The other is the vibration of PVA-PAA gel film in ac fields. This new deformation suggests a gel having a fast response on the order of 100 ms. 

Fig. 13a, b. Biomimetic actuators using electric field-responsive gels a robot hand having four smart gel fingers which can hold a quail egg, and b artificial fish with a tail of gel film which can swim under ac electric fields... 

Particular cases are potassium selective potentiometric sensors based on cobalt [41] and nickel [38, 42] hexacyanoferrates. As mentioned, these hexacyanoferrates possess quite satisfactory redox activity with sodium as counter-cation [18]. According to the two possible mechanisms of such redox activity (either sodium ions penetrate the lattice or charge compensation occurs due to entrapment of anions) there is no thermodynamic background for selectivity of these sensors. In these cases electroactive films seem to operate as smart materials similar to conductive polymers in electronic noses. 

In conclusion, the unique properties of Prussian blue and other transition metal hexa-cyanoferrates, which are advantageous over existing materials concerning their analytical applications, should be mentioned. First, metal hexacyanoferrates provide the possibility to develop amperometric sensors for non-electroactive cations. In contrast to common smart materials , the sensitivity and selectivity of metal hexacyanoferrates to such ions is provided by thermodynamic background non-electroactive cations are entrapped in the films for charge compensation upon redox reactions. 

PMMA-based films (Senotop) already used for the Smart City Coupe roof... 

Development of a glossy, aesthetic and unpainted roof module on the Smart Roadster by DaimlerChrysler AG s Smart. The two-piece, removable roof, built by ArvinMeritor, is surfaced with a thermoformable three-layer film (Lexan by GE Plastics) that can be co-moulded with either thermoplastic or thermoset substrates. The film exhibits 95% gloss retention after the equivalent of 10 years of Florida sun exposure. Weight saving is 50% versus a painted steel roof system. 

Interest has developed in electrochromic light transmission modulators, which are called smart windows , for control of temperature and lighting in buildings and automobiles. A cross section of an electrochromic light transmission modulator is shown in Fig. 11.31 (Rauh and Cogan, 1988). The two electrochromic elements of the structure are designated ECl and EC2, and are sandwiched between two thin film, optically transparent, electrodes of ITO and separated by an electrolyte. The ECl layer should colour when a negative potential is applied and the EC2 layer should either colour under positive potentials or remain in a transparent state. This is indicated by the chemical reactions ... 

Figure 1. Smart dust mote and its components Micro-fabricated sensors, optical receiver, signal-processing and control circuitry the power source consists of a solar cell and a thick-film battery. (Derived with permission from ref 16. Copyright 2001 IEEE)...

A calculation of the power requirements of the smart dust mote underscores our point that the present generation of batteries cannot effectively power this device. Thin-film batteries are among the most advanced of the lithium battery systems, with a capability to scale down to dimensions on the same order of magnitude as the cubic millimeter of the dust mote. 3 The energy density for the thin-film system is 2 J mm , which matches or exceeds standard lithium ion systems, such as those that power laptop computers. A key design requirement for the smart dust mote is that the power consumption cannot exceed 10 juW. If the dust mote uses this power continuously over a day, it will consume 1 J. 

Can a thin-film battery supply the 1 J per day of energy necessary to power a smart dust mote At first glance, it would appear that there should be no problem the device consumes 1 J mm and the... 

The energy per unit area as reported for several lithium thin-film batteries ranges from 0.25 to 2 x 10 2 J mm. Thus, thm-fiim batteries, despite their excellent energy per unit volume, fall far short of being able to power a smart dust mote for 1 day. If the areal footprint were made 100 times larger (at 1 cm ), the thin-film approach would be acceptable. The consequences of the 2-D nature of thin-film batteries are easily overlooked. The calculation by Koeneman et al. ignored the 2-D character of thin-film batteries when they concluded that these batteries could carry out some 60 000 actuations of a smart bearing ." When one considers the actual area available for the power source on the device, only about 1200 actuations are possible. 

While the amount of electricity that can be conducted by polymer films and wires is limited, on a weight basis the conductivity is comparable with that of copper. These polymeric conductors are lighter, some are more flexible, and they can be laid down in wires that approach being one-atom thick. They are being used as cathodes and solid electrolytes in batteries, and potential uses include in fuel cells, smart windows, nonlinear optical materials, LEDs, conductive coatings, sensors, electronic displays, and in electromagnetic shielding. 

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