July 24, 2007
Gecko + Mussel Mashup = 'Geckel' Ultimate Nanoadhesive
Scientists at Northwestern University, led by Phillip B. Messersmith, associate professor of biomedical engineering, unveiled their "geckel nanoadhesive" in work published July 19, 2007 in Nature magazine, considered important and interesting enough by Nature's editors to have merited the coveted cover (above).
Here's the editor's summary.
- Geckos with Mussel
On the cover, a gecko clings to a mussel shell. This improbable scenario stems from a shared ability of these species to cling on to things. Geckos can adhere even to inverted surfaces, thanks to tiny hairs on their feet. But the grip is temporary, as rapid attachment and detachment are key to locomotion. It has proved difficult to make a synthetic that stays sticky over many cycles and there is another snag: a gecko's adhesion is much reduced under water. A new adhesive, called 'geckel', overcomes this sensitivity to water by combining gecko-type nanostructures with the chemical approach to underwater adhesion used by mussels. The resulting hybrid adhesive, made up of an array of tiny pillars coated with a polymer that mimics the wet adhesive proteins found in mussels, shows remarkable reversible adhesion over 1,000 cycles in both wet and dry conditions. This development could lead to reversible adhesives suited to a range of practical applications.
Here's a link to a press release (which follows) describing their creation.
- Nature's secrets yield new adhesive material
Scientists report they have merged two of nature’s most elegant strategies for wet and dry adhesion to produce a synthetic material that one day could lead to more durable and longer-lasting bandages, patches, and surgical materials. As published in this week’s issue of the journal Nature, the scientists, supported by the National Institute of Dental and Craniofacial Research (NIDCR), part of the National Institutes of Health, have designed a synthetic material that starts with the dry adhesive properties of the gecko lizard and supplements it with the underwater adhesive properties of a mussel. The hybrid material, which they call a geckel nanoadhesive, proved in initial testing to be adherent under dry and wet conditions. It also adhered much longer under both extremes than previous gecko-based synthetic adhesives, a major issue in this area of research.
According to the authors, their findings mark the first time that two polar opposite adhesion strategies in nature have been merged into a man-made reversible adhesive. “Our work represents a proof of principle that it can be done,” said Phillip Messersmith, D. D.S., Ph.D., a scientist at Northwestern University in Evanston, Ill. and the senior author on the paper. “A great deal of research still must be done to refine the fabrication process and greatly reduce its cost. There’s no reason to believe that these improvements can’t be achieved, but it’s going to take time.”
Dr. Messersmith said the inspiration for the geckel nanoadhesive came about two years ago when he noticed an article about the adhesive force of a single hair from the foot of gecko. As lizard fans have long marveled, geckos climb walls and other dry, steep surfaces not by producing a glue-like substance but through a natural adaptation of the hairs that cover the soles of their feet.
Roughly one-tenth the thickness of a human hair, each gecko hair splits multiple times at the end. These split ends contain cup-like structures called spatulae that vastly increase the hair’s surface area. Whereas a human hair touches a surface just once, the gecko makes multiple contacts with the suction-like spatulae. With roughly a half million hairs on each foot, scientists estimate a gecko has a billion spatulae at work as it scampers up a wall.
Messersmith knew that researchers have attempted for several years to produce synthetic adhesives based on the adherence strategy of the gecko. What caught his eye in this article is gecko adhesion doesn’t work well in water. Messersmith, who studies the underwater adhesion of mussels, had an idea. What if each synthetic gecko-inspired polymer, called a pillar, was coated with a man-made adhesive protein inspired by the mussel" As Messersmith mused, nobody had ever tried it and, if successful, this hybrid approach might spawn a new and potentially superior direction in designing temporary adhesive materials.
As reported in Nature, Messersmith’s idea turned out to be correct. He and his colleagues designed a small nanopolymer array that mimicked the natural spatial patterns of the hair on the foot of a gecko. They then coated their creation with a thin layer of a synthetic compound. This unusual compound mimics the reversible bonding action of a mussel adhesive protein that Messersmith’s group has studied for the past several years.
In their initial experiments, which were led by graduate student Haeshin Lee, they found that the wet adhesive force of each pillar increased nearly 15 times when coated with the mussel mimetic and applied to titanium oxide, gold, and other surfaces. The dry adhesive force of the pillars also improved when coated with the compound.
“That actually wasn’t so surprising to us,” said Lee, the lead author on the study. “The mussel-inspired adhesive is extremely versatile in that it can bond reversibly to inorganic surfaces under wet and dry conditions.”
As Lee noted, the next research hurdle was whether their hybrid geckel nanoadhesive would continue to stick to surfaces after multiple contacts. This has been a major challenge with other gecko-based adhesives. They typically stick well at first but lose their ability to adhere after a few cycles of contact with a tipless cantilever.
Using the cantilever and repeatedly touching it down, Lee developed a camera to visualize the process down to individual pillars. He found that the geckel hybrid maintained 85 percent of its adherence under wet conditions after 1,100 contacts with the tip. Under dry conditions, the level of adherence was 98 percent.
“This isn’t quite a home run, but it’s somewhere in between a double and a triple,” said Lee, who devised on his own a special imaging devise to visualize individual pillars during the experiments.
Messersmith said that while the results are extremely promising, his group still must tackle several practical problems before it can scale up its research. “Any time that you fabricate an array of nano pillars of this type over large areas, you must have a very effective way of doing it without losing the efficacy of the approach,” said Messersmith. “We’ll also need to reduce the fabrication costs to make geckel commercially viable.”
But Messersmith said he envisions great possibilities for geckel. “Band aids already adhere well, except if you go swimming, take a shower, or somehow expose it to a lot of water,” said Messersmith. “So I think the most important thing with this adhesive is the added value of resisting immersion in water.”
“I should add that the essential component of the wet adhesive polymer on the pillars contains a chemical that we have discovered last year adheres well to mucosal surfaces, such as those inside our mouth,” he noted. “It may be possible to develop patches in the future that can be applied on the inside of the cheek to cover damaged tissue.”
Now that you're all warmed up, you're ready for the publication's opening paragraph, which follows.
- A reversible wet/dry adhesive inspired by mussels and geckos
The adhesive strategy of the gecko relies on foot pads composed of specialized keratinous foot-hairs called setae, which are subdivided into terminal spatulae of approximately 200 nm. Contact between the gecko foot and an opposing surface generates adhesive forces that are sufficient to allow the gecko to cling onto vertical and even inverted surfaces. Although strong, the adhesion is temporary, permitting rapid detachment and reattachment of the gecko foot during locomotion. Researchers have attempted to capture these properties of gecko adhesive in synthetic mimics with nanoscale surface features reminiscent of setae; however, maintenance of adhesive performance over many cycles has been elusive, and gecko adhesion is greatly diminished upon full immersion in water. Here we report a hybrid biologically inspired adhesive consisting of an array of nanofabricated polymer pillars coated with a thin layer of a synthetic polymer that mimics the wet adhesive proteins found in mussel holdfasts. Wet adhesion of the nanostructured polymer pillar arrays increased nearly 15-fold when coated with mussel-mimetic polymer. The system maintains its adhesive performance for over a thousand contact cycles in both dry and wet environments. This hybrid adhesive, which combines the salient design elements of both gecko and mussel adhesives, should be useful for reversible attachment to a variety of surfaces in any environment.
Bonus: Nature offers a weekly podcast featuring the most interesting reports in each week's journal: this week's features the "geckel nanoadhesive," among others.
Free — the way we like it.
Dog Lunch Box
After a dog's breakfast thoughts inevitably turn to lunch, right?
What better way to make sure your one true friend gets what he deserves when you're on the road than this integrated solution?
From the website:
- Dog Lunch Box
Traveling dog food container is a convenient and versatile "take along."
Designed for the pet — and pet lover — on the go, the lid of the Dog Lunch Box is intended to hold dry food on one side and fresh water on the other.
Bucket holds up to 30 lbs. of food and features a carry handle.
Just perfect for long road trips!
12" x 15" x 10".
Dress your toothpaste
Garden Drill — Because fun in the dirt is the best kind
Time to bring your drill upstairs and outside, what?
From the website:
- 3-Piece Garden Drill Auger System
Auger attaches to your 3/8" or 1/2" cordless or electric drill to easily dig holes and break up hard, compact soils for a variety of yard projects.
Plant bulbs, aerate compost piles, cut through roots for removal of dead shrubs.
Dig up to 3-ft. deep post holes effortlessly.
Use as a rototiller for small gardens.
Also great for mixing concrete, paint, or potting soils.
It's the most versatile garden tool you'll own.
System includes 3"-diam. and 4"-diam. augers and 26" extension.
Rarely have I featured an item that cries out "Flautist, Flautist" more insistently than this nifty bit o' kit.
BehindTheMedspeak: Artificial Spinal Disks
Barnaby J. Feder's July 18, 2007 New York Times article about new artificial cervical spine (neck) disks from Medtronic (above and below) caught my eye, mostly because the currently approved artificial lumbar spine (low back) disks have proved to be "a disappointment."
The prosthetic disks are lauded as being superior to spinal fusion, a difficult and demanding (for both patients and surgeons) procedure.
I'm an anesthesiologist with some expertise and experience in anesthesia for spine surgery and the thing that jumps out at me as an informed observer of the closest kind is that the downside of a disaster at the level of the cervical spine dwarfs that of trouble down below in the lumbar region.
Consider worst case scenarios: loss of function from the waist vs. the neck down.
Here's the Times story.
- 2nd Medtronic Neck Disk Wins Panel Approval
Medtronic, which late Monday became the first medical device maker cleared to sell an artificial neck disk in the United States, may also become the first company to sell a device that would compete with it.
An independent panel of orthopedics experts recommended late yesterday by a 7-1 vote that the Food and Drug Administration approve the second device, the Bryan cervical disk [above], a newer design. The company says the Bryan more closely resembles a natural spinal disk than the Prestige ST disk that the F.D.A. cleared for sale a day earlier.
Both the Prestige and Bryan devices are already in use in Europe.
Analysts said that the expert panel’s recommendation was unlikely to translate into full F.D.A. approval of the Bryan before winter, but yesterday’s vote confirmed Medtronic’s commanding head start in the race to move artificial disk technology from the lower spine, where the products have been a disappointment, into the upper spine, where many doctors think the disks have a better chance of becoming a popular alternative to spinal fusion.
Estimates of the number of cervical, or upper spine, fusions performed annually in the United States are as high as 250,000.
Although Wall Street expects a cautious response from insurers and surgeons to lead to slow growth initially, some analysts say the market for the cervical devices could eventually top $1 billion.
The news yesterday was not all good for Medtronic, though. In a separate development, the F.D.A. posted on its Web site a warning letter that the agency sent the company last week detailing a range of device safety reporting and monitoring violations at the Minneapolis factory where the company makes implantable pumps to control pain.
Among other things, the agency cited Medtronic for failing to follow up on at least 37 reports from doctors, patients or patient’s families of potential injuries like lower limb paralysis that may have been linked to problems with the pumps. The company received a separate F.D.A. warning letter about manufacturing violations at the same plant last year. Medtronic, which is based in Minneapolis, said it was working with the agency on both warnings.
While spinal products have been an important growth area for the company, its primary focus remains cardiovascular devices like its implanted defibrillators and the drug-coated Endeavor stent, which it expects to bring to the American market within the next year.
Artificial cervical disks like Prestige and Bryan can relieve conditions like numbness in the arms or the disabling pain sometimes associated with degeneration of the disks in the upper spine. Such relief can often be obtained by fusing the bones around the diseased disk if rest, drugs and exercise fail to help. But patients receiving the disks may recover more quickly than those who undergo fusion and often retain more flexibility in their necks.
“We wanted to place our bets in more than one area,” said Peter L. Wehrly, president of Medtronic’s spinal and biologics group, when asked why the company had invested in two different cervical disk designs.
The Prestige is made of stainless steel, while the Bryan consists of a dense polymer core and titanium end plates meant to more closely resemble a natural disk. The Prestige is approved for replacing only a single disk. The company said the Bryan was likely emerge as the better design for patients needing multiple disks replaced.
Skeptics said doctors may be reluctant to steer patients away from fusion because of its high success rate and relatively good insurance coverage. Cervical disk implantation is likely to end up costing patients — or insurers — about as much as fusion surgery, which is about $32,000, according to Medtronic.
Screen Patch Repair Kit
Once, when I had some time on my hands and found myself doing something close to nothing, but different than the day before, I decided to fix a hole in my screen door.
I got out my small surgical forceps and pointed tweezers and spent a happy hour or so aligning, straightening and flattening the messed up wire grid, such that after I'd finished I couldn't see the repair unless I got up real close to it.
You may not feel the same way about this sort of thing being the highest and best possible use of your time.
I understand, which is why I present to you this alternative.
From the website:
- Screen Patch Repair Kit
Skip the hardware store — these peel-and-stick patches fix screens in seconds, keeping bugs out!
Just cut to fit, peel off self-stick backing, press on hole and rub, for quick repair of holes and tears.
Transparent mesh PVC blends into screen.
Kit includes eight 6-1/4"L x 4-7/8"W patches.
Hardiness Zone Time Machine
When you press "Play" here you see a three-second-long video
depicting the movement north of plant hardiness zones
in the U.S. from 1990 to 2006.
Happi-Helper: 'Whip, beat, turn, mix, blend, chop, drain, strain, cut, serve, remove frost in your freezer — even scrapes paint!'
A blast from the past — more precisely, July 30, 2006.
At the time it was $1.49.
Still not a bad deal at twice the price, what?
From the website:
This multipurpose kitchen tool looks like a slotted spatula with a sharpened edge.
But here's what it can do (take a deep breath): whip, beat, scrape, turn, mix, blend, chop, drain, strain, cut, and serve brownies and cakes, remove frost in your freezer — even scrapes paint.
Note added June 25, 2007 at 8:17 p.m.: My crack research team — paid a ginormous amount of money (not to mention perks like use of the bookofjoe company jet, stock options, et al.) to drill down and find the very best price for items that make their way here — failed yet again.
It took a helpful link, just in, from Michael Lien, president of Remote Control Technology Inc. — who no doubt has a million and one better things to do than stuff like this — to learn that the item has apparently just been reduced to fly out of the warehouse at last year's sweet $1.49.
At that price you could do like Michael did and buy a bunch to give away to people who think they have everything.