A reciprocating linear actuator driven by anti-phototaxis of plankton

Abstract

This study focuses on the development of a reciprocating linear actuator driven by plankton. The actuator consists of a straight channel groove in a base plate and a small float with a fin for channel separation. On both sides of the separated channel, plankton freely swims. When the channel is alternatively illuminated by light sources installed at both ends, the plankton escape from the light because of their anti-phototaxis and collide against the fin, resulting in actuation of the float. As an experimental example of plankton, matured Artemia sallina (brine shrimp) was used because of its anti-phototaxis nature, as well as its suitable physical size and the breeding convenience. Because of the small driving capacity of the float, two types of reciprocating mechanisms without mechanical load were designed and examined. One type has an optical switching system that is a combination of the shade on the float and optical fibers arranged along the channel. This system drives the float according to the switching of the light; however, a dead point exists where the brightness of the illumination becomes equal. The other type is based on an electronic switching system using photo-interrupters and a flip-flop, enabling continuous reciprocation. An average float speed of 0.21mm/s and a driving force of 0.537mN per plankton were obtained in an experiment using 15 Artemia adults. An average round-trip travel time of 69.3s was obtained for the linear reciprocation. Thus, the possibility of a plankton-driven mechanism is demonstrated, although further research on fatigue and habituation of the plankton is required.