"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." https://patentimages.storage.googleapis.com/12/1d/09/0fb416e99018cf/US5393602.pdf
This is the upper picture here:
We decrease the pH, the system lifts the weight, we increase the pH, the system returns to its initial state and a new lifting can start. The work we possibly waste in decreasing and increasing the pH can be reduced to zero if the process is carried out quasistatically. Then lifting the weight is the net work involved in the isothermal cycle, in obvious violation of the second law of thermodynamics.
Systems of this kind are commonplace:
"Gels are known to change their volume in response to alteration of the environmental parameters. The change in volume results from the absorption or release of the fluid and may reach hundreds and even thousands percent. Often it is accompanied by considerable swelling force. Gels that demonstrate substantial (and often abrupt) volume change in response to small environmental change and gels that are selective to a specific stimulus are called stimuli-responsive or responsive gels (SRGs)...The amount of mechanical work that the gel is able to produce is important for applications where the gel is employed as an actuator. The work is proportional to both generated force and displacement..." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5365095/
"Extraction of mechanical work from stimuli-responsive molecular systems and materials. Molecular switches and advanced molecular motors, which are the elementary building blocks for the construction of molecular machines, have been recently integrated into soft materials in order to generate macroscopic actuation under various types of external stimulations." https://hal.science/hal-03418854/document
In most cases the mechanical work is extracted under isothermal conditions, and this, although still not a proof per se, is a strong suggestion that the second law of thermodynamics is violated (the extracted mechanical work is arguably greater than the work wasted in activating and deactivating the stimulus). Will theoretical physicists and theoretical chemists ever consider a stimulus-responsive system producing mechanical work isothermally? No. Such a system acts like the face of Medusa the Gorgon - on seeing it, theoreticians get petrified and never recover.
This is the upper picture here:
We decrease the pH, the system lifts the weight, we increase the pH, the system returns to its initial state and a new lifting can start. The work we possibly waste in decreasing and increasing the pH can be reduced to zero if the process is carried out quasistatically. Then lifting the weight is the net work involved in the isothermal cycle, in obvious violation of the second law of thermodynamics.
Systems of this kind are commonplace:
"Gels are known to change their volume in response to alteration of the environmental parameters. The change in volume results from the absorption or release of the fluid and may reach hundreds and even thousands percent. Often it is accompanied by considerable swelling force. Gels that demonstrate substantial (and often abrupt) volume change in response to small environmental change and gels that are selective to a specific stimulus are called stimuli-responsive or responsive gels (SRGs)...The amount of mechanical work that the gel is able to produce is important for applications where the gel is employed as an actuator. The work is proportional to both generated force and displacement..." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5365095/
"Extraction of mechanical work from stimuli-responsive molecular systems and materials. Molecular switches and advanced molecular motors, which are the elementary building blocks for the construction of molecular machines, have been recently integrated into soft materials in order to generate macroscopic actuation under various types of external stimulations." https://hal.science/hal-03418854/document
In most cases the mechanical work is extracted under isothermal conditions, and this, although still not a proof per se, is a strong suggestion that the second law of thermodynamics is violated (the extracted mechanical work is arguably greater than the work wasted in activating and deactivating the stimulus). Will theoretical physicists and theoretical chemists ever consider a stimulus-responsive system producing mechanical work isothermally? No. Such a system acts like the face of Medusa the Gorgon - on seeing it, theoreticians get petrified and never recover.