Smart materials: Fused liquid marbles show their strength

Jul 31, 2013
Smart materials: Fused liquid marbles show their strength
Confining water droplets inside metal-organic liquid marbles could make cosmetic and personal care products easier to apply. Credit: iStockphoto/Thinkstock

'Liquid marbles' are a peculiar new substance made by rolling water droplets into powders incapable of dissolving in water. The resulting micro- and nanoscale-particles act like soft solids, and can speed along surfaces without leaving water marks. Such non-stick, hydrophobic behavior has potential application in drug-delivery and microfluidic technology. However, liquid marbles suffer from erratic structures prone to collapse. Jia Min Chin, Jianwei Xu and co-workers from A*STAR's Institute of Materials Research and Engineering, and Institute of Bioengineering and Nanotechnology, have now developed a scheme to stabilize liquid marbles quickly and safely using vapors from ordinary superglue.

Many powders used to make liquid marbles are based on metal–organic frameworks (MOFs), a type of crystal in which are interspersed with rigid . Chin, Xu and co-workers investigated whether MOFs known as NH2-MIL-53(Al), a combination of aluminum atoms and amino-phenyl compounds, could grow directly on the surfaces of alumina microparticles. This approach, the team theorized, might provide extra structural control over liquid marble stability. After confirming MOF growth with x-ray measurements, the team modified the microparticles with either hydrocarbon or fluorocarbon chains, converting them into 'superhydrophobic' powders. Then, they produced alumina-supported liquid marbles by adding micro-sized .

The researchers found that their new liquid marbles had greater stability than usual, thanks to its reactive amino groups and high surface roughness. Yet, they sought to further boost its resilience. When they spotted small gaps between the MOF–alumina microparticles with , they inferred that certain might enter these pores and create a cross-linked network through a process called air–liquid interfacial polymerization.

Forensic scientists often use superglue vapors to uncover fingerprints at crime scenes; the trace water in finger smudges reacts rapidly with adhesive fumes and generates visible polymer structures. Taking a cue from this method, the team exposed their MOF–alumina liquid marble to superglue vapors in a Petri dish and saw a rigid polymer casing form within a few minutes. Chin notes that this procedure requires no heat, UV radiation, or chemical initiators—an unprecedented finding for liquid marble encapsulation. "Furthermore, the only solvent required was water, qualifying this as a 'green' reaction," she adds.

The liquid marble retained its unique non-wetting behavior on surfaces, even with the protective polymer coating. These stabilizing attributes promise big dividends in areas such as gas purification and personal care products: two patents have already been filed this year in efforts to commercialize this technology.

Explore further: Researchers build 3-D structures out of liquid metal

More information: Chin, J. M., et al. Supergluing MOF liquid marbles. Chemical Communications 49, 493–495 (2013). dx.doi.org/10.1039/c2cc37081f

add to favorites email to friend print save as pdf

Related Stories

Researchers build 3-D structures out of liquid metal

Jul 09, 2013

(Phys.org) —Researchers from North Carolina State University have developed three-dimensional (3-D) printing technology and techniques to create free-standing structures made of liquid metal at room temperature.

Water droplets prefer the soft touch

Jun 25, 2013

(Phys.org) —Researchers have found a way to drive water droplets along a flat surface without applying heat, chemicals, electricity, or other forces: All that's required is varying the stiffness of the ...

Recommended for you

A greener source of polyester—cork trees

Apr 16, 2014

On the scale of earth-friendly materials, you'd be hard pressed to find two that are farther apart than polyester (not at all) and cork (very). In an unexpected twist, however, scientists are figuring out ...

User comments : 0

More news stories

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.