Algae-like Artificial Organic Phototactic Micro-swimmers

TL;DR

This paper introduces a novel class of algae-like organic micro-swimmers that exhibit complex phototactic behaviors, self-assembly, and reversible disassembly, mimicking biological algae and opening avenues for bio-mimetic applications.

Contribution

It reports a new organic nano-structure-based micro-swimmer with self-assembly, phototaxis, and reversible disassembly, created via a simple pyrolysis process, mimicking algae behavior.

Findings

Exhibits positive and negative phototaxis under weak light.

Forms fractal-like dynamic colonies and patterns.

Disintegrates under strong light, enabling control over assembly.

Abstract

Phototaxis is a light driven self-locomotion of mass and a common phenomenon in motile organisms with varieties of motility such as in bacteria, algae, etc. In naturally occurring organisms, mechanical force is generated utilising their metabolic energy to propel and swim in presence of light, performing important bio-chemical reactions. Herein, we report a new class of micro-swimmers that exhibit captivating and complicated micro-swimming mediated colony formation properties resembling green algae. A facile pyrolysis reaction is explored leading to homogeneous organic Nano-structures forming patterned self-assemblies among themselves. A delicate balance of colloid surface forms interesting architectures such as dynamic colonies, thallus like patterning and cilia like micro-arms. In presence of weak light both positive and negative phototaxis are seen moving the micro-swimmers propelling towards and away from the light respectively. During swimming helical motion and electrostatic interactions of colloidal micro-swimmers with neighbouring assemblies are observed. The nature of assembly formation is found to be fractal and can be disintegrated using strong light. Strong exposure stimulates predominately fast negative phototaxis leading to directional propulsion along the light path. All these algae life-like behaviour of the colloidal carbonaceous lyophilic colloids are stable in alcohol and can be reversibly discontinued with water due to super-hydrophilicity. We therefore introduce a class of life-like colloidal chemical architecture. Our discovery may entice studies for creation of a diverse programmable micro-swimmers for microscopic understanding and manipulating collective effect of the assemblies for bio-mimetic and catalytic applications.