2017-11-30 12:22:25 UTC
An artificial muscle obviously able to produce an unlimited amount of work:
"Artificial muscle basic-motion"
Is the device a perpetual-motion machine of the second kind? In this particular case there is no information how the work-producing force is activated. If, in increasing and then decreasing the work-producing force, the experimentalist loses less work than he gains from weight-lifting, then, yes, the device is a perpetual-motion machine of the second kind. In other words, if the net work extracted from a cycle is positive, the second law of thermodynamics is violated.
Here we do have the needed information - work-producing cycles will occur if the pH of the system is regularly changed:
"pH-Responsive Hydrogel Composite Artificial Muscle. Here we see a pH-responsive polyacrylic acid hydrogel contained within an unbound carbon fibre braid. The artificial muscle (McKibben style) actuates when placed in a solution with high pH, generating contraction free strains of ~30%."
All pH-sensitive polymers are potential perpetual-motion machines of the second kind:
"When the pH is lowered (that is, on raising the chemical potential, μ, of the protons present) at the isothermal condition of 37°C, these matrices can exert forces, f, sufficient to lift weights that are a thousand times their dry weight." http://www.google.com/patents/US5520672
A. KATCHALSKY, POLYELECTROLYTES AND THEIR BIOLOGICAL INTERACTIONS, p. 15, Figure 4: "Polyacid gel in sodium hydroxide solution: expanded. Polyacid gel in acid solution: contracted; weight is lifted." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1367611/pdf/biophysj00645-0017.pdf
Consider Figure 4 in Katchalsky's article. The following four-step isothermal cycle, if carried out quasi-statically (reversibly), clearly violates the second law of thermodynamics:
1. The polymer is initially stretched. The experimentalist adds hydrogen ions (H+) to the system. The force of contraction increases.
2. The polymers contracts and lifts a weight.
3. The experimentalist removes the same amount of H+ from the system. The force of contraction decreases.
4. The experimentalist stretches the polymer and restores the initial state of the system.
The net work extracted from the cycle is positive unless the following is the case:
The experimentalist, as he decreases and then increases the pH of the system (steps 1 and 3), does (loses; wastes) more work than the work he gains from weight-lifting.
However electrochemists know that, if both adding hydrogen ions to the system and then removing them are performed quasi-statically, the net work involved is virtually zero (the experimentalist gains work if the hydrogen ions are transported from a high to a low concentration and then loses the same amount of work in the backward transport). That is, the net work involved in steps 1 and 3 is zero, and the net work extracted from steps 2 and 4 is positive, in violation of the second law of thermodynamics.