Charles W. Wolgemuth, http://physics.aps.org/articles/v4/4
"The busy life in living cells involves a great deal of transport activities and mechanical tasks, which are undertaken by motor proteins* —molecular machines that convert chemical energy into mechanical work. In recent years, these remarkable machines have inspired artificial devices that deliver mechanical work or propel themselves in a viscous environment. We do not yet understand the mechanism behind the complex mechanochemical coupling in motor proteins. Standard rules used in macroscale engineering do not work at the nanoscale. New strategies are needed for the development of artificial nanoscale machines." http://physics.aps.org/articles/v3/108
*Motor proteins are a class of molecular motors that are able to move along the surface of a suitable substrate. They are powered by the hydrolysis of ATP and convert chemical energy into mechanical work. more http://en.wikipedia.org/wiki/Motor_protein