Artificial muscle valves

Tsai, H.-K. A., Xu, H., Zoval, J. and Madou, M. (2005) Bi-layer polypyrrole artificial muscle valves for drug delivery systems, SPIE Smart Structures and Materials, Electroactive Polymers and Devices (EAPAD), 6-10 March 2005, San Diego, CA. 

Degradation of hydrocarbons between 1000 and 2000 C yields an isotropic form of coal. This pyrolytic coal is suitable for use in artificial organs, as, for example, in artificial heart valves. It is compatible with muscle fiber and blood proteins and consequently causes little blood coagulation. 

Recent papers have explored producing faster responses by inducing porosity into the gels. While the application as artificial muscles is not practical, low stress applications, such as sensors and valves, are possible [176]. Lenses and light modulators have been demonstrated recently [177, 178]. 

Companies dedicated to the development of artificial muscles based on conjugated polymers have also emerged in recent years. MicroMuscle based in Sweden and EAMEX from Japan are both actively pursuing actuators for biomedical and electronics apphcations. Santa Fe Science and Technology, USA, has produced continuous spun polyaniline fibres and demonstrated their use as linear actuators [11, 12]. Academic laboratories have also developed several demonstration products including a variable camber hydrofoil [13], a robotic fish propulsor fin [14], a gas valve [15], microrobots [16] and a micropump [10], some of which are illustrated in Figure 10.1. An electronic Braille screen using ICP actuators is also described in this book [17]. 

One of the problems faced in applying PNlPAAm hydrogels is that the response rate to temperature changes is very slow, which restricts their wider applications, such as on-olf valves and artificial muscles. According to the Tanaka-Fillmore theory [168], where t, R, and D... 

Responsive polymers, especially hydrogels, combine both sensor and actuator characteristics. Nevertheless, to date there are only a few devices on the market, because response time can be slow, the materials are weak, and greater precision needs to be developed. Intriguing applications are being explored including the creation of artificial muscle using chemomecha-nical transducers and their use in thin films where response time is not so critical. Other applications include the use of micro- and nanogels and particles in applications such as photonic crystals, microlens systems, dmg delivery vehicles, and microfluidic valves. 

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