A platform for stop flow gradient generation to investigate chemotaxis published in Angewandte Chemie

A controlled gradient of hydrogen peroxide is generated in a microfluidic chip where a precise pressure retroactive loop prevents any external flow to interfere with the chemotaxis response of catalytic microswimmers. (Image by A. Nsamela.)
A platform for stop flow gradient generation to investigate chemotaxis
Z. Xiao, A. Nsamela, B. Garlan, and J. Simmchen
Angew. Chemie Int. Ed., Feb. 2022
chemRxiv: 10.26434/chemrxiv-2021-sxqm1
DOI: 10.1002/anie.202117768

The ability of artificial microswimmers to respond to external stimuli and the mechanistical details of their origins belong to the most disputed challenges in interdisciplinary science. Therein, the creation of chemical gradients is technically challenging, because they quickly level out due to diffusion. Inspired by pivotal stopped ow experiments in chemical kinetics, we show that microfluidics gradient generation combined with a pressure feedback loop for precisely controlling the stop of the flows, can enable us to study mechanistical details of chemotaxis of artificial Janus micromotors, based on a catalytic reaction. We find that these copper Janus particles display a chemotactic motion along the concentration gradient in both, positive and negative direction and we demonstrate the mechanical reaction of the particles to unbalanced drag forces, explaining this behaviour.

David presented an oral contribution at PHOTOPTICS 2022

Snapshot of the motion of an ellipsoid in a double beam optical trap. (Image by D. Bronte Ciriza)
Optical systems are ubiquitous in modern society, with an ever-increasing number of applications covering medical sciences, spatial exploration, information processing and industry, to name but a few examples. In this context, David presented his work on machine learning enhanced optical forces calculations at PHOTOPTICS 2022 between the 10th and the 11th of February. The conference took place online and it was the perfect opportunity to learn from other scientists and discuss the relevance of optics for the study of active matter systems.