Direction and velocity control of gliding microtubules using a microdevice made of SU-8/Cu composite

In this study, we report on the fabrication of microscale structures that induce photothermal effects using SU-8/Cu composite material and evaluate the directional changes in microtubule movement relative to these structures, as well as velocity changes in response to the irradiance of excitation light. Evaluation of the temperature rise in SU-8/Cu composite structures under excitation light showed a proportional relationship between temperature increase and irradiance, with a maximum rise of 9.5°C at 43.2 W/cm2. Microtubule motility experiments conducted on the fabricated device revealed that the average probability of microtubules changing their movement direction along the structure was 61%. Microtubule velocity was higher in regions closer to the SU-8/Cu composite structures than in more distant regions. Additionally, the velocities measured at irradiances of 1.0 W/cm2 and 43.2 W/cm2 were 0.308 µm/s and 0.464 µm/s, respectively, indicating a maximum increase of 1.5 times. These findings suggest that integrating directional and velocity control mechanisms for microtubule movement onto a single substrate is feasible. Furthermore, they demonstrate the potential utility of the fabricated device as a system capable of simultaneously observing and controlling microtubule movement using a microscopic observation system.