Design and evaluation of Artemia-driven micro ratchet gears

This paper describes the design and evaluation of Artemia-driven micro ratchet gears and the results of performance evaluation. Larval-stage Artemia sallina (brine shrimp) were used in the experiments because they exhibit positive phototaxis and are more easily cultured within a shorter time than adults. The shrimp photactically migrated toward the gear surface, whose outskirts were partially illuminated by an aperture mask. Because the contour was asymmetric, the collision impacts on the ratchet surface generated a rotation torque. Gears were fabricated from an ultra-violet (UV) cured resin using a 3D printer. The appropriate gear radius (2.5 mm) and thickness (1.5 mm) were experimentally determined. Phototaxis was effectively enhanced by brightness control on the gear surface, achieved by painting the surface. The dependences of rotation speed on the Artemia population number and illumination wavelength were examined. A population density of 300 Anemia in 4 mL of culture medium under blue light illumination yielded the maximum speed (0.4 rpm). Long-term rotation without feeding and medium exchange was also evaluated and was maximized at 40 h. Because the small torque was difficult to be measured directly, it was simulated by a drag force model. The result (0.24 mu Nm) is reasonably consistent with previous measurements using adult Artemia. (C) 2015 Elsevier B.V. All rights reserved.