New concept of a hydrophobicity motor based on local hydrophobicity transition of functional polymer substrate for micro/nano machines

Abstract

Abstract Hydrophobic interaction is widely known as one of the most important forces acting between biomolecules. This paper proposes a new concept of driving mechanism for macromolecules or microscale objects, such as hydrogel particles as a biomimetic motor. The idea is based on not only utilizing a tangential gradient of hydrophobicity of the substrate but also that such a gradient should be induced by energy input from the environment through the motor unit. Assuming a simple model for a hydrophobicity motor, numerical analysis revealed the basic dynamical behavior. The movement of the motor was in many cases oscillatory and in certain special conditions, a constant speed motion. The force-velocity curves consisted of three regions: the region simply decreasing with load, the sustaining region for large load with zero speed and the yielding region. This result is very similar to that of muscle contraction. This concept could be the engineering basis for handling biomolecular interactions.