Programmable artificial micro-swimmer

Introduction It has attracted much interest to design a self-powered artificial nanorobotic system which mimic the behavior of the motile bacteria due to both scientific merits as well as its potential applications.... [ view full abstract ]

Introduction
It has attracted much interest to design a self-powered artificial nanorobotic system which mimic the behavior of the motile bacteria due to both scientific merits as well as its potential applications. Previously, it has been demonstrated that asymmetric redox reaction on bi-metallic nanowire can produce the electric field and propel itself in solution. This autonomous motion shows that artificial inorganic nanomaterial can be used as nanomotor which harvests energy from the environment.

Methods
Here, we will present a rational designed micro-swimmer based on Janus nanotree which harvests energy from absorbed photons by photoeletrochemical (PEC) reaction. Our micro-swimmer incorporated both photocathode and photoanode. Upon illumination, the photoelectrochemical reaction on the swimmer surface generates the asymmetric ionic enviroments required to propel the migration of micro-swimmer.

Results
In this design, we focus on controllability and programmability of the micro-swimmer. The Individual Janus nanotree is designed that it can sense the direction of light vector and direct to illumination direction. Since the migration is regulated by the surface potential of micro-swimmer, we developed a simple chemical modification process to program the swimmer to show either positive phototaxis (migrates towards the light source) or negative phototaxis (migrate away from the light source).

Discussion
Two main advantages have been demonstrated in this light powered micro-swimmer. First, light can be used not only as the power source but also as a new method to control the migration of individual swimmer which provided another option besides magnetic control. Second, since the energy is provided from the light, it is easier to find a biocompatible redox shuttle to replace the widely used toxic H2O2, which would promise wider applications for micro/nanomotor.

Reference:

B. Dai, J. Wang , Z. Xiong, X. Zhan, W. Dai, C.C. Li, S. Feng, J. Tang, Programmable Artificial Phototactic Microswimmer, Nat. Nanotechnol. AOP

Figure caption
a. Schematic of micro-swimmer. b. The trajectory of a pristine nanotree spells “nano” as navigated by light. c. Sequential images of the green algae, E. Gracilis, pristine microswimmer, CSPTMS treated micro-swimmer suspension in aqueous solution with illumination from the right side