Conical frustum gel driven by the Marangoni effect for a motor without a stator

The Marangoni effect has inspired the development of diverse applications such as robots, gel motors, and self-propelled droplets. A major challenge for the developed gel motors is the need for stators, which dampen the rotating velocity and reduce the motor lifetime due to frictional forces from the stators. Therefore, we developed a new type of gel without a stator to realize rotating motions, namely, a conical frustum gel. In this work, we initially studied the principle of the rotated gels driven by the Marangoni effect. For comparison, we designed two types of gels: cylindrical and conical frustum gels. Then we devised mathematic models to estimate the generated torques. The two gels were synthesized. Additionally, both the oil and aqueous fluids were prepared. Next, we investigated the influence of a chemical on the moving duration of the gels. The circular motion trajectories of the gels were compared and analyzed. Finally, we researched the angular velocities and driving torques generated by the two gels. This work should contribute to the development of a non-stator gel motor powered by the Marangoni effect.