Soft Matter Blog

Soft Matter lectureship award winner Eric Furst talks to Chemistry World writer Jennifer Newton.

Who or what inspired you to become a scientist in the first place?
It was in my blood – I came from a family of engineers so I was exposed at a very early age to science and engineering. I was almost pre-destined in that sense. As a kid, I was inspired by visits to the air and space museum as well as the Space Program here in the US. I even had a picture of the Space Shuttle Columbia over my bed.

Your research is focused on soft matter. What attracted you to that field?
It happened when I was an undergraduate at Carnegie Mellon University, where there was a tremendous group of faculty, including Bob Tilton who I worked with directly. They had a wonderful program on colloids and polymers and that’s when I really got hooked. I started to study polymer adsorption and interfaces and read a lot in the literature about polymer thermodynamics. It’s an area with engineering applications, something that I am obviously interested in. The physical chemistry of the systems is so neat and profound. I also really enjoyed the more fundamental side to it.
I then went on to do a PhD at Stanford University, working with Alice Gast, and that was her area. It has always been a subject that a lot of engineers work on, especially in the US, but it is also a fertile ground of chemists, physicists and materials scientists and I really like that multi-disciplinary aspect of the soft matter community.

You’ve been awarded the 2013 Soft Matter lectureship. How does that feel?
It’s tremendous. It’s amazing recognition and I’m honoured by it. When you look at the names associated with the award, many of whom I know personally, they’re great young leaders in the field. I’ve found the soft matter area to be my intellectual home and I’m really excited to have that sort of exposure.

What do you class as your most important contribution to the soft matter field?
I can tell you about my favourite contributions. One of them has been microrheology. This is an area that actually dates back almost 100 years with people looking at Brownian motion, including Einstein. About 20 years ago now, Dave Weitz and Tom Mason had the idea that you can use this motion to learn about the rheology of materials and the rheology of systems. I think we’ve made some really nice contributions to that in terms of the gelation of biomaterials. Along with my collaborators, we’ve been able to show how microrheology can be used to screen materials to get an understanding of their physical properties and their rheology. It has a gorgeous engineering aspect to it and it fits nicely into the ideas that people have for screening materials and creating libraries of materials. There is some beautiful underlying physics in the problem too.
Another contribution we’ve made is to do with the directed self-assembly of materials. How can we get things like nanoparticles or colloids to self-assemble into unique structures? There is a tremendous amount of work going on in this area right now. And we’ve been able to show how fields can be useful to direct self-assembly.

What do you imagine will be the next big breakthrough in your field?
Along the lines of directed self-assembly, a major breakthrough will be when we get predictive capabilities. Materials chemists have been extremely creative at making particles with different shapes and with different directing interactions. Right now we are sitting on a cusp where we have an enormous library. To make the leap to manufacturing to make real materials that are functional would have huge benefits. Self-assembled nanomaterials are very scalable and would become very low-cost. It’s a very enabling type of technological advance. Things like the Materials Genome Initiative and increases in computational power are giving us a tool box to make those advances.

Is there a particular question you are trying to answer in your lab at the moment?
Not exactly. One of things I love about soft matter is that I can be as unfocused as I want!
We do want to better understand directed self-assembly. I think we’re at the tip of the iceberg for finding the building blocks and pathways that lead to certain structures.
We’re also really interested in protein therapeutics and that just shows the breadth of the problems you can tackle with soft matter research. For years, my research group has focussed on rheology – the flow of materials – and with that comes microrheology, which is a really enabling method to study the stability and the viscosity of protein solutions. With protein therapeutics emerging in the market place we could help develop upstream processes to identify proteins and the best way to manufacture them. We have a project with industry on protein therapeutics that is a little more directed to engineering applications and actually getting things to market.

What’s your favourite piece of equipment in your lab?
It’s got to be the laser tweezers we’ve been using for the past 12 years. Picking things up with light never gets old. It’s one of those wacky things. We’ve used them in complex fluids to pull things apart and glue things together. Microscopy is an important technique for soft matter but to be able to go in and prod things – that adds an extra dimension. You can see what it looks like but what happens when I poke it?

Have you got a favourite material that you like to work with?
Colloids. Colloidal suspensions are so unique. They’re building blocks, they’re little rheometers, so many of the things we use on a day-to-day basis have a colloidal component.

What advice do you have for young scientists?
Look for opportunities. Look for the people who are going to mentor you. Watch what they do and remember that. Students and young people need to figure out what they’re excited about. Get in laboratories, discover things and ask questions.

Can you tell us a little known fact about yourself?
I really enjoyed being a radio DJ in my undergraduate and graduate days. Music has always been a tremendous part of my life. Breaking boundaries in music is a lot like science. You’re always asking, “what don’t I know?”

The interview with Eric Furst was first published in Chemistry World.
http://www.rsc.org/chemistryworld/2013/06/interview-eric-furst-soft-matter-rheology

An injectable nanocomposite gel for replacing the eye lens could eliminate the need for complicated cataract surgery, say Japanese and Danish researchers.

The nanocomposite fills the capsular bag left in the eye after the lens has been removed and sets into a gel at body temperature

Cataracts are caused by optical defects of the natural lens that develop with age and can lead to increasingly blurred vision and blindness. Currently, plastic lenses can be used to surgically replace the natural lens but they are not a perfect replacement, for example they tend to be monofocal, limiting the eye’s ability to focus outside a set range. They are also not a proper fit, which can cause problems such as misalignment.

Read the full article in Chemistry World

Organic–inorganic nanocomposite gels as an in situ gelation biomaterial for injectable accommodative intraocular lens
Masahiko Annaka, Kell Mortensen, Toyoaki Matsuura, Masaya Ito, Katsunori Nochioka and Nahoko Ogata
Soft Matter, 2012, Advance Article
DOI: 10.1039/C2SM25534K

Prolonged CO release for peptide-based gel compared to soluble peptide

Scientists in the US have created a gel that can be used to deliver therapeutic carbon monoxide gas to selected organs in the body.  

CO has a role in the body as a biological signalling molecule (as a neurotransmitter and a blood vessel relaxant, for example) and its delivery to tissues for therapeutic use for conditions such as cardiovascular disease and organ transplantation is done by inhalation therapy. This technique is risky, though, as overexposure to CO in this way can be poisonous, and the CO cannot be targeted to any organs other than the lungs.

More recently, small molecule CO-releasing molecules (CORMs) have been developed as an injectable targeted delivery method. However, the molecules – commonly used metal carbonyls, and the more recent polymeric micelles – have short half-lives and are not retained in tissues, which limits their use.

Samuel Stupp from Northwestern University, and colleagues, who previously developed self-assembling peptide-based materials to deliver another biological signalling molecule – NO – have now turned their attention to the problem of delivering CO. His team combined a peptide amphiphile (PA) designed to self assemble into a fibrous gel with a ruthenium carbonyl complex similar to a known CORM. They reacted the resulting compound with sodium methoxide to generate the CO-releasing PA. The PA self-assembled into nanofibres 8.2nm in diameter.

The CO release performance of the soluble PA gave a similar half-life to known CORMs.  The PA was, however, designed to form a gel, which was achieved by adding CaCl₂ to the solution. ‘Gel formation slowed down CO release dramatically, from a half-life of 2.1 min for the soluble peptide to 17.8 min after gelation,’ says Stupp. This prolonged release could significantly improve the utility of CO therapy.

‘This work will add to the regenerative medicine toolbox by enabling researchers to modulate biological signalling through the delivery of a very simple diatomic gas,’ says Stupp.

Bing Xu, an expert in bionanomaterials for drug delivery from Brandeis University, US, says that the system’s future development could lead to a material that significantly outperforms current CORMs. ‘The demonstration of the delivery of therapeutic CO expands the horizon of PA applications,’ he adds.

A peptide-based material for therapeutic carbon monoxide delivery
John B. Matson, Matthew J. Webber, Vibha K. Tamboli, Benjamin Weber and Samuel I. Stupp
Soft Matter, 2012, Advance Article
DOI: 10.1039/C2SM25785H

Read the original Chemistry World article here.

Scientists in India – inspired by research on making water run uphill – have developed a technique that enables a polymer cylinder to not only autonomously climb an incline but carry a weight with it.

There are a number of different approaches towards limbless locomotion, but they focus on using mechanical or chemical pulses to drive a body forwards. Researchers from the Indian Institute of Technology in Kanpur have taken another approach: rolling.

A sequence of images captured at 0, 1.43 and 2.87 seconds (top to bottom) showing a 4mg polymer cylinder dragging a 18mg screw across a horizontal surface

The team, led by Animangsu Ghatak, used the swelling interactions of an elastomeric cylinder and a solvent to drive the cylinder forward. When the solvent is released, it spreads along the cylinder and swells at the contact points, particularly at the ends. This pushes the centre of mass forward and the rest of the cylinder moves to keep up via a rolling motion, which drags solvent with it. Because of this rolling motion, dry polymer is brought into contact with the solvent and swells in turn. The saturated polymer is exposed to the air and the solvent evaporates, forming a swelling-evaporation-de-swelling mechanism and enabling autonomous movement as long as the solvent lasts.

The most unusual aspect of the system, Ghatak explains, ‘is that gravity can be used to increase the asymmetric effect and thus the resultant increase in velocity’. By increasing the incline, ‘the solvent tends to accumulate more in the rear side of the cylinder than in the front and as a result, the asymmetric effect becomes more pronounced and the cylinder bends more’. This greater bend not only increases the velocity but creates enough torque for the cylinder to carry a dead weight with it.

Mark Geoghegan, from the University of Sheffield, UK, points out that although this technique will not scale up to the macro-scale, the field of self-powered locomotion is still very young. ‘This is an exciting area of research and one expects the benefits to be reaped only years in the future,’ he says.

Both Geoghegan and Ghatak can also see more immediate uses for the technology – despite the early days – and highlight potential roles in sensing or soft robotic components.

Read the original Chemistry World article, or watch the supplementary video

Researchers in Japan have made a crab shell transparent. Then, using knowledge gained from this activity, they created a transparent nanocomposite sheet, incorporating powdered chitin from crab shells. The nanocomposite could have applications in devices that need a high light transmittance, such as flat panel displays.

Scientists have previously used cellulose from plants and chitin to strengthen materials, giving biologically-inspired nanocomposites. If natural nanofibres are dispersed widely enough in a transparent polymer matrix, they can strengthen the polymer and the resulting nanocomposite material will retain its transparency. Work on optically transparent polymers containing cellulose nanofibres shows they have a low axial thermal expansion coefficient, meaning their size does not vary with temperature, making them ideal for use in flexible flat panel displays and solar cells. Interested to know more? Read the full article in Chemistry World here…

Preparing the transparent crab shell: (a) original shell, (b) shell after removal of matrix substances and (c) transparent crab shell after immersion in acrylic resin

The transparent crab: preparation and nanostructural implications for bioinspired optically transparent nanocomposites
M I Shams, M Nogi, L A Berglund and H Yano
Soft Matter, 2012, Advance Article
DOI: 10.1039/c1sm06785k

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US scientists have devised a method of generating 3D structures from flat surfaces by printing patterns onto a polymeric children’s toy and letting an IR heat lamp do the rest.

Polymers that are responsive to an applied stimulus have attracted interest in a variety of areas, and polymers that self-fold have potential applications in packaging, mechanical actuation, sensors and drug delivery.

Shape memory polymers, which return to a pre-programmed form upon a threshold temperature or other stimulus, suffer from limited movement and require complex syntheses, as the parts of the polymer that respond to the synthesis must be chemically different to the panels that move. This new technique, however, uses conventional black printer ink to print a hinge onto a cheap and readily available pre-stressed polystyrene polymer. Interested to know more? Read the full article in Chemistry World here…

(i) A Shrinky Dink; (ii) unidirectional folding via absorption of light by black ink patterned on one side of the Shrinky Dink; (iii) bidirectional folding due to ink on both sides of the Shrinky Dink. Owing to effective light absorption by the ink, the polymer under the black ink heats up faster than the rest of the polymer

Self-folding of polymer sheets using local light absorption
Y Liu, J K Boyles, J Genzer and M Dickey
Soft Matter, 2011
DOI: 10.1039/c1sm06564e

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Soft Matter paper highlighted in Chemistry World:

US researchers have made nanowires that can be propelled through liquids with an external magnetic field. The wires could be used to deliver drugs in the human body.

Eric Lauga and Joseph Wang from the University of California San Diego and colleagues made the nanoswimmers by attaching nickel heads to gold tails. They used a magnetic field to propel the wires through human serum, which means that they have potential for use in biomedical applications, such as targeted drug delivery, as no chemicals or fuel sources are required…. Read the rest of the article here.

The way that we digest fat could be controlled by food design, providing potential health benefits, according to scientists from Australia.

Fat is an essential part of our diet, but too much of it can lead to problems such as heart disease and obesity. The digestion of fat is also involved in triggering the hormone signals that tell us whether or not we are full. Reducing fat intake in meals is often negated by overeating, so designing food that controls fat absorption is of great interest.

Micrographs showing structural changes occurring in the emulsion immediately after preparation (left), 30 minutes after incubation at pH 1.9 in simulated gastric fluid (middle) and 30 minutes after subsequent incubation at pH 6.8 in simulated intestinal fluid

Researchers at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Food and Nutritional Sciences designed fat emulsions using different surfactants, including protein, phospholipids and common food additives, and monitored how their structures changed during simulated digestion. They also gave the emulsions in a drink form to healthy volunteers and monitored blood triglyceride levels, which give an indication of how the fat is being digested by the body.

To view the full Chemistry World article, please click here: Designer foods

Link to journal article

Impact of gastric structuring on the lipolysis of emulsified lipids
Matt Golding, Tim J. Wooster, Li Day, Mi Xu, Leif Lundin, Jennifer Keogh and Peter Clifton, Soft Matter, 2011
DOI: 10.1039/c0sm01227k

Sticky hydrogels make resilient wound dressings

An adhesive material made from a hydrogel filled with nanoparticles could lead to wound dressings that won’t fall off when you sweat. It could even be used to deliver drugs through skin, claim French scientists.

Traditional wound dressings lose their ability to stick to skin in the presence of water – a major component of sweat – shortening their lifespan. Now, scientists led by Bruno Grassl from the University of Pau and Pays de l’Adour have developed adhesive materials based on hydrogels to overcome this problem. Hydrogels contain a large quantity of water already, which allows them to tolerate the additional water from sweat; however, their mechanical properties, such as elasticity, are often poor. Interested to know more? Read the full article for free in Chemistry World here.
 

Nadia Baït, Bruno Grassl, Christophe Derail and Ahmed Benaboura, Soft Matter, 2011, DOI: 10.1039/C0SM01123A (Advance Article)