Zewei Zhao,Zhiguang Wu,Sven Rutkowski,Sergei I. Tverdokhlebov,Johannes Frueh
Micropumps are in animal and human bodies and on cellular levels vital for the life functions. In case of critical problems like diseases, artificial micropumps are candidates to take over important functions. These functions are ranging from release of substances over removing toxics to stirring stomach fluids, helping to disperse medicine. We hereby present a Janus micropump, powered by hydrogen bubbles, which is able to operate in a gastric pH environment. This Janus micropump consumes hydrochloric acid as an external fuel and releases magnesium ions , which act as micronutrients . The presented Janus micropumps do display significant pumping power by moving external tracer particles and stop after exhausting their magnesium or alternatively acid fuel. The pumping properties depend significantly on the surrounding pH environment and the amount of external surfactant added. Analysis of tracer particle motion shows, that the cause of this movement are the bubbles generated that drag the liquid along after bubble release.
Zewei Zhao,Tieyan Si,Anna I. Kozelskaya,Igor O. Akimchenko,Sergei I. Tverdokhlebov,Sven Rutkowski,Johannes Frueh
The speed and motion directionality of bubble-propelled micromotors is dependent on bubble lifetime, bubble formation frequency and bubble stabilization. Absence and presence of bubble stabilizing agents should significantly influence speed and propulsion pattern of a micromotor, especially for fast-diffusing molecules like hydrogen. This study demonstrates a fully biodegradable Janus structured micromotor, propelled by hydrogen bubbles generated by the chemical reaction between hydrochloric acid and magnesium. Six different concentrations of hydrochloric acid and five different concentrations of the surfactant Triton X-100 were tested, which also cover the critical micelle concentration at a pH corresponding to an empty stomach. The Janus micromotor reverses its propulsion direction depending on the availability and concentration of a surfactant. Upon surfactant-free condition, the Janus micromotor is propelled by bubble cavitation , causing the micromotor to be pulled at high speed for short time intervals into the direction of the imploding bubble and thus backwards. In case of available surfactant above the critical micelle concentration, the Janus micromotor is pushed forward by the generated bubbles, which emerge at high frequency and form a bubble trail. The finding of the propulsion direction reversal effect demonstrates the importance to investigate the motion properties of artificial micromotors in a variety of different environments prior to application, especially with surfactants, since biological media often contain large amounts of surface-active components.
危险品化学品经营许可证（带存储）