Embedding magnetic particles within water droplets enables the liquid to exhibit remarkable behaviors such as climbing steps, traversing obstacles, and initiating chemical reactions. This precise control has potential applications in drug delivery and the development of advanced lab-on-a-chip technologies.

Shilin Huang and his team at Sun Yat-sen University in China engineered a surface featuring minute grooves coated with a superhydrophobic varnish, making it highly resistant to wetting. [1] Understanding that water droplets placed on such grooves can autonomously leap upward due to the pressure disparity between the droplet's deformed bottom within the narrow channel and its less constrained, rounder top.

Figure 1. New Technique Enables Precise Steering of Water Drops Through Obstacle Courses and into Chemical Reactions

Figure 1 Show in “New Technique Enables Precise Steering of Water Drops Through Obstacle Courses and into Chemical Reactions". The researchers aimed to induce the pressure difference at will. They introduced a minuscule magnetic particle into each droplet and positioned an electromagnet beneath the groove. Activating the electromagnet attracted the particle, and consequently, a portion of the droplet, into the groove. Deactivating the electromagnet caused the droplet's shape to rebound, propelling it upward akin to being launched from a slingshot.

Embedding minute magnetic particles within regular water droplets transforms them into agile performers, capable of scaling steps, hurdling obstacles, and initiating chemical reactions. This precise manipulation holds promise for applications in drug delivery and the advancement of intricate lab-on-a-chip technologies. Shilin Huang and his team at Sun Yat-sen University in China devised a surface featuring minuscule grooves coated with a superhydrophobic varnish, rendering it highly resistant to wetting. Recognizing that water droplets placed atop such grooves can spontaneously leap upward due to the pressure differential between the droplet's deformed bottom within the narrow channel and its less constrained, rounded top.

To achieve this, the team introduced minuscule magnetic particles into each droplet and positioned an electromagnet beneath the groove. Activating the electromagnet attracted the particle, along with a portion of the droplet, into the groove. Upon deactivation, the droplet's shape rebounded, propelling it upward akin to being launched from a slingshot. Using this method, the researchers successfully guided liquid droplets to hop up millimeter-scale stairs and traverse miniature obstacles. [2] They even directed a droplet into a narrow gap between two wires, thereby completing a circuit and illuminating a light bulb.

Xiao Yan from Chongqing University in China lauds this innovative approach as a means to exert precise control over pressure-induced droplet movement, potentially serving as a valuable tool for accurately transporting chemical droplets. In one experiment, researchers directed a droplet to leap into and blend with a liquid chemical sample beneath a microscope lens, allowing them to observe the ensuing chemical reaction in real time. In another instance, they facilitated the mixing of two droplets with a third inside a sealed enclosure, initiating a reaction remotely. This method circumvented the need for manual intervention, preserving the reaction's integrity by preventing air exposure that could compromise the results.

The meticulous control over chemical processes holds promise for applications in drug delivery. Huang envisions the technique advancing "lab-on-a-chip" technologies, which aim to miniaturize complex biochemical experiments typically conducted in large spaces with extensive glassware. He suggests the concept of "lab-on-stacked-chips", where droplets vertically leap between levels, enabling numerous reactions to occur simultaneously in parallel.

References:

1. https://news.knowledia.com/GB/en/articles/water-purifier-is-powered-by-static-electricity-from-your-body-c4a33d0aa23e570ffbf31c39824d623b061bc28a
2. https://www.newscientist.com/article/2419169-magnetic-particles-turn-water-droplets-into-tightrope-walking-acrobats/

Cite this article:

Janani R (2024), Magnetic Particles Transform Water Droplets into High-Wire Performers,Anatechmaz,pp.923