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July 27^th is National Scotch Whisky Day in the United States. Why was today chosen for this particular honor? No one seems to know or care, however, most seem to appreciate the excuse to sample Scotland’s liquid gold.

Scotland takes its whisky production very seriously.  Understandably so - aqua vitae pumps nearly £5 billion into the Scottish economy annually. The Scotch Whisky Regulations of 2009 ensure that the quality of that whisky is upheld. Scotch whisky is a chemically complicated drink, containing hundreds of different compounds - the most important flavor compounds are derived from the barley (raw material), the yeast involved in fermentation, and the oak casks used for aging.

The process begins when barley grain is malted; moistened, allowed to germinate, then dry-heated to stop germination. Then, the grain is ground to a grist. Next, malted barley is added to water in a tun and mashed. The mashing process takes place at a range of controlled temperatures allowing the enzymes in the grist to convert starches into sugars; it takes approximately three days to convert the sugar into alcohol. The resulting liquid is called "wort," generally pronounced in Scottish distilleries as "wert."

Next, the alcohol is transferred to copper stills. Why copper? It is easy to mold, conducts heat efficiently and is corrosion-resistant. Most importantly, the copper catalyzes chemical reactions which remove highly volatile sulfur compounds and help form the esters that impart a fruity character.

Distillation produces three fractions: the foreshots, which contain acetaldehyde, methanol, and ethyl acetate; the spirit, which will be aged into whisky; and the feints, which contain low volatility compounds like phenols.

For most malt Scotch whisky, the feints and the foreshots are discarded, and the spirit is distilled a second time, while Irish whiskey is distilled three times. However, some Scotch whiskies are two and a fraction or triple distilled. The decision of where to cut the feints is important, or you would lose all the phenolic smokiness of the Islay whiskies.

After distilling, Scotch whisky must age for at least three years; maturation time varies depending on the distillery.  Whisky casks are made of European or American oak and have already been used to make bourbon, sherry or port. The type of predecessor liquid influences the flavor of the finished product. Cask size must be less than 185 gallons to ensure the necessary additive, subtractive and interactive reactions between the wood and the whisky. During these reactions, more sulfur compounds are removed, alcohols and aldehydes are oxidized, and acids react with ethanol to create esters. Since the desired concentrations of these reactions only occur at a certain temperature and humidity range, the regulations state that Scotch whisky must be aged within Scotland.

Aging in wooden casks is also what gives whisky its liquid gold appearance. If the melanoidins from the degrading timber don’t brown the whisky sufficiently, caramel is the only additive allowed by the Scotch Whisky Regulations to achieve the expected color.

After the requisite aging, the whisky is bottled. Although the glass is unreactive, the liquid inside is still volatile, and subject to oxidation, reduction and redox reactions (i.e. temperature, sunlight and movement).

How to Drink It

Neat

If you like cereal tones or smoked aroma, drink your malt whisky without diluting it.

Diluted with Room Temperature Water

Adding room temperature water will lessen the ethanol concentration. Some members of the whisky drinking community have asserted this “opens up” the drink, making flavor compounds more available.

With Ice

Adding ice or cold water is controversial. Proponents argue ice reduces the volatility of the flavor compounds; you will smell the flavor compounds less, but you will still taste them. Most whisky drinkers believe that adding ice and lowering the temperature merely ruins the Scotch, interfering with both aroma and taste.

So celebrate at your local pub with a dram (a.k.a. glass of whisky). Oh, and the Scotch Whisky Regulations of 2009 require us to remind you - drink responsibly and never drink and drive. Slàinte mhath!

As children, we learn that to skip a stone across a lake or puddle, we need to have a fairly flat stone. We also learn that a ball thrown at a pool, usually at one’s brother, tends to bury itself into the water rather than skipping. The makers of the Waboba (which stands for ‘water bouncing ball’) have made an interesting use of the viscoelastic nature of polymers to cross the line between a thrown ball and a skipping stone. Look at various videos on-line of the Waboba, and you will see that a thrown Waboba will skip across a flat body of water with equal, or some would say, more enthusiasm than a stone. And it is less painful to catch on the other side.

So how does it work? Unlike balls that are rigid and inflexible, the Waboba will deform and flatten when subjected to a compressive force. When a ball is thrown at a shallow angle into the water, it generates a depression in the water as the entrance force ejects water out of the flat layer. If the ball is inflexible, it will present a small surface area to the backside of the depression in the water, causing the ball to penetrate into the water and eventually sink. A flat stone, on the other hand, presents a larger surface area, allowing the stone to plane on the backside of the water depression and fly out of the depression.

The Waboba enters the water as a spherical ball, but then flattens as the compressive forces generated by the kinetic energy of the thrown ball being counteracted by the resistance of the water. The flattened ball then behaves like the flat stone, and planes out of the water depression. The designers of the Waboba needed to work out the proper range of compressive properties. Interestingly, the harder the ball is thrown into the water, the more it should flatten and hence achieve greater planing behavior.

This important research was conducted 5 years ago by Tadd Truscott, a professor at BYU, who clearly recognized the critical need of explaining why, from strict engineering principles, toys are fun. Videos of Dr. Truscott’s work can be found here, with stills from the video shown below.

Stone entering water, creating depression.

The stone rides up the back of the depression and flies out.

A rigid ball entering the water, creating a depression.

The smaller surface area pushes the ball deeper into the water.

Waboba entering the water, flattening under the compressive force of the ball hitting the back of the water depression.

The Waboba exiting the water depression and resuming its more spherical shape.

It isn’t only Ghostbusters that have to worry about being slimed! Last Friday, chaos ensued when 3,400 kg of hagfish were accidentally deposited on a highway in Oregon.

This slimy traffic accident reminded us of work we performed a few years ago in collaboration with Prof Douglas Fudge on understanding quite what is going on when these animals are disturbed.  These evolutionary throwbacks are generally considered the vultures of the deep sea, feeding off carcasses and debris at the bottom of the ocean.  Their skin is often used as a faux eel-skin, but to an engineer the most fascinating aspect of this animal is the slime it produces.  When attacked, the animal responds by generating copious amounts of slime; although relatively small animals, they can generate gallons of gel almost instantaneously. 

It turns out these animals have evolved this spectacular defense based on two physiological components.  There are 150-200 slime glands spaced along the body of the animal.  In each gland are thread cells of about 150 microns in size, but composed of a single wrapped 1-3 micron filament that is 10 -20 cm long.  Along with this cell are high molecular weight mucous glycoproteins in vesicles.  These components expand rapidly upon exposure to water; the vesicles provide an elastic gel-like matrix, while the fibers entangle and hold the gel together.

We performed rheology on hagfish glycoproteins in an attempt to understand the assembly and gelation mechanisms (presented at the Society of Rheology in 2003) with evidence of a yield stress and elasticity, and a strong salt influence.  In the end though, perhaps the most interesting aspect is the manner in which the hagfish clears itself – it simply ties itself in a knot and “slides” the gel off itself.   

We are approaching the 60^th anniversary of a very important milestone that coupled the unpresuming plastic industry with the world of kitsch: the development of the pink plastic lawn flamingo.  The lawn flamingo was invented by the appropriately and presciently-named Donald Featherstone. Mr. Featherstone, after graduating from the Worcester Art Museum, took a job with a plastic lawn ornament manufacturer in Leominster, MA, a town 1 hour from Cambridge Polymer Group’s headquarters. Leominster has a long history in plastic production, earning the nickname ‘Comb City’ based on its production of celluloid-based combs in the late 1800s. Injection molding also got its start in Leominster, pioneered by Samuel Foster, who made, amongst other items, injection molded sunglasses that go by the name ‘Foster Grants’.  Lastly, Leominster can claim to be the home of Tupperware, the happily burping container system still in vogue.

So pink plastic lawn flamingos were a natural fit for Leominster. Fittingly, Mr. Featherstone received an Ig Nobel Prize for his work in 1996, an award that celebrates both invention and humor, with a smattering of sarcasm. As an interesting aside, Mr. Featherstone and his wife wore matching outfits for 35 years; not terribly relevant, but interesting. Although Mr. Featherstone left this mortal coil in 2015, we are comforted knowing the world he left is a bit pinker and more plasticky.  The flamingos continue to appear in modern culture and on the bolder homeowner’s lawn. Students at the University of Wisconsin were treated to the sight of over 1000 plastic flamingos adorning Bascom Hill on campus in 1979, courtesy of the student government. This event prompted Madison, WI, home of the UW campus, to name the lawn flamingo its official bird in 2009.

So join the plastics world in thanking Mr. Featherstone for this unassuming but important contribution.

Development of synthetic tissue models has been gaining speed over the past decades as materials, designs, and processing techniques have become more sophisticated. Polyurethane and silicone organ models adorn the desktops of many scientists and physicians, and serve as useful anatomical images and guides. For actual surgical technique development and training, these rigid materials sometimes do not accurately replicate the behavior of biological tissue. Alternative materials, most notably hydrogels, can function well in this role. The highly hydrated nature of hydrogels can give them the feel, elasticity, and cutting behavior of native tissue, and they can often be prepared in form factors that mimic the native organs. CPG has been developing custom tissue models for over 20 years for clients based on its proprietary hydrogel formulations.

Skin is a challenging organ to model, since it has unusual elasticity and frictional behavior when compared to other tissues, such as muscle and fat. Beyond just mechanical behavior, researchers are keenly interested in skin models that help assess biological safety requirements. The standard approach for biological safety is normally an animal model (rat, rabbit), but public resistance to animal testing has pushed for development of non-animal based models. L’Oreal is using additive manufacturing techniques to make films of skin models derived from human keratinocytes, producing a model that is histologically similar to the human epidermis. Intended to allow L’Oreal to test their skin products, the EpiSkin™ model is proposed for tests in involving irritation, UV exposure, DNA damage, and other parameters.

A company local to Boston, MatTek, has also been producing EpiDerm™ skin models for several years by culturing human keratinocytes.

These technologies present an exciting platform for reproducible, clinically-relevant skin testing without the need for animal models.

Are you selecting materials for use in a medical device and feeling overwhelmed by the dizzying array of material options?  In this webinar, Dr. Brian Ralston shares the process CPG uses to help clients select and test materials to minimize risk and maximize safety, efficacy, and prospects for regulatory approval. 

Brian Ralston, Ph.D., P.E., researches and consults on the analysis and processing of polymeric materials and their physical and chemical behavior in products, with a focus on biomedical devices. His expertise spans numerous analytical methods including mechanical, thermal and chemical characterization, failure analysis, design assessment, fractography, statistics, accelerated aging, and development of novel test methods and fixtures.

This webinar is targeted towards:

• Medical device manufacturers
• Medical device engineers
• Process engineers
• Quality engineers
• Regulatory personnel

Duration: 30 minutes

MINIMIZING RISK IN MEDICAL DEVICE MATERIAL SELECTION

Wednesday, May 31, 3 p.m., Eastern Standard Time

To register, click here