Converting microscale linear to rotary motion in kinesin-powered systems

Converting linear to rotary motion is a typical and enabling task for macroscale machinery, but the process is not yet established at the nano- and microscale. Linear motion is generated by the motor proteins kinesin and dynein as they move along microtubules, and a microtubule immobilized on the circumference of a microsphere could create rotary motion as it is propelled by surface-adhered motors, enabling microscale machines such as “active ball bearings”. This paper describes the attachment of microtubules to microspheres and the resulting types of motion as the microtubule-microsphere assemblies interact with a surface covered with kinesin-1 motor proteins. Dragging, pushing, spinning and rotating motions are observed and analyzed, demonstrating a pathway to microscale rotations driven by linear biomolecular motors.