A remotely controlled Marangoni surfer

Abstract

Inspired by creatures that have naturally mastered locomotion on the air–water interface, we developed and built a self-powered, remotely controlled surfing robot capable of traversing this boundary by harnessing surface tension modification for both propulsion and steering through a controlled release of isopropyl alcohol. In this process, we devised and implemented novel release valve and steering mechanisms culminating in a surfer with distinct capabilities. Our robot measures about 110 mm in length and can travel as fast as 0.8 body length per second. Interestingly, we found that the linear speed of the robot follows a 1/3 power law with the release rate of the propellant. Additional maneuverability tests also revealed that the robot is able to withstand 20 mm s−2 in centripetal acceleration while turning. Here, we thoroughly discuss the design, development, performance, overall capabilities, and ultimate limitations of our robotic surfer.

Functional Chemical Motor Coatings for Modular Powering of Self-Propelled Particles

“…Figure a shows the surface tension difference between water γ 0 and the fuel/water mixture γ fuel as a function of the fuel concentration for several solvents. Although most solvents can generate high gradients when applied directly as highly concentrated solutions (e.g., as droplets of pure fuel, which is a common approach − ), the gradients are very small at low concentrations. Considering that in a swimming body, the fuel source will be constantly moving and new fuel will be released in fresh medium, we can assume that the chemical motors will always operate in a very low concentration regime .…”

“…This evasion strategy from insects has inspired scientists to develop a variety of biomimetic propulsion mechanisms for robotic platforms across length scales, ranging from microscale active droplets , to large scale multicomponent systems. , These methods generally consist in the release of a chemical fuel (surfactants or low surface tension solvents) to the air–water interface at specific locations and at specific rates and durations (including thermal-based Marangoni propulsion methods) . To support the advancement of Marangoni-based propulsion systems, many different materials and strategies have been developed and adopted over the years in surface swimming robots with varying degrees of success, performances, and limitations: including the direct delivery of pure chemical fuel to the air–water interface − and their encapsulation in a matrix ,, for controlled release. The direct application of fuel at the interface (delivery of pure solvent drop by drop) requires impractical delivery mechanisms and high volumes of fuel reservoirs (which reduces the autonomy and efficiency of the propulsion system and hinders its miniaturization).…”

Marangoni‐Propulsion Micro‐Robots Integrated with a Wireless Photonic Colloidal Crystal Hydrogel Sensor for Exploring the Aquatic Environment

“…Thus, it is thought that the smaller micro-robot could still propel by the Marangoni effect. In the case of larger micro-robots, previous works have successfully propelled large robots (length: %100 mm) [16,37] by using other fuels. Therefore, the larger Marangoni-propulsion robots can also propel by using different fuels with larger surface tension and optimizing the robot designs.…”

Culinary fluid mechanics and other currents in food science

“…The same mechanism can be used to create microscopic swimming droplets [249], which can be used as cargo carriers that move deep inside complex flow networks [250]. Recently, Dietrich et al [251] developed very fast Marangoni surfers that can swim over ten thousand body lengths per second, and Timm et al [252] developed Marangoni surfers that can be remotely controlled. More generally, similar phoretic effects [253], where interfacial flows are driven by gradients in concentration, electric fields, temperature etc., can be exploited to make a broad range of self-propelled colloids that are of extraordinary interest to understand collective dynamics and emergent phenomena out of equilibrium [254][255][256][257][258][259][260].…”