| Research Abstract |
In order to create biomimetic motility systems, polymer gels have been employed using their reversible size and shape change, thereby realizing the motion by integrating the deformation on a molecular level. Along this line, several kinds of artificial soft machines have been constructed using synthetic polymer gels, such as gelooper (gel-looper), gelf (gel golf), gel valves, chemical motor, shape memory gel, artificial muscle, artificial heart. Motivated by these research results, we have succeeded in obtaining hydrogels with a high mechanical strength as 10 MPa sustaining more than millions of continuous wearing test with little wearing due to their extremely low frictional coefficient. These gels might open new era of soft ＆ wet materials for substituting articular cartilage and other tissues of human body.
By comparing the behaviors of gel machine with the solid machine, the specific features of the soft and wet machine have been elucidated. For example, if a gel has free dangling charged polymer chains on its surface, the frictional coefficient becomes as low as 10^<-4>, which is lower than that of animal articular cartilage.
We have successfully created an ATP fueled soft gel machine reconstructed from muscle proteins of actin and myosin. Chemically cross-linked actin gel filaments, several thousand times the volume of native actin filaments (F-actin) move along a chemically cross-linked myosin fibrous gel (1 cm long and 50 μ m in diameter) with a velocity as high as that of native F-actin, by coupling to ATP hydrolysis. The muscle protein-gel demonstrates that one can reconstruct a soft machine fueled by chemical energy by using actin and myosin molecules as elementary elements.
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