THE RIGHT KIND OF

CASE STUDIES

(FOR ENGINEERS)

ILLUMINATING BLOOD VESSELS VEINLITE

A man, a frustrating project, and insomnia — these three components came together in a fortuitous way the night Nizar Mullani had his breakthrough idea. A professor at the University of Texas Medical School, with a grant from National Institutes of Health, Mullani had been putting the lion’s share of his energy into developing a device called the Nevoscope, a tool to help doctors detect cancerous skin lesions. The Nevoscope had proved highly viable, except for one problem: its mode of transillumination made blood vessels very visible, obscuring the images of the skin lesions.

Mullani pondered during sleepless nights and perhaps because he was at his wit’s end, his tired brain tossed him a novel idea: Nevoscope aside, was there also a need for a device that illuminates blood vessels to a high degree?

It turns out there was.

Mullani developed Veinlite, a stripped down version of the original Nevoscope. The Veinlite is now used in many medical settings, increasing accuracy in finding and accessing veins by almost 10 percent. It is particularly important in treatment of patients whose veins may be difficult to detect and access, such as the elderly, infants, and the obese.

CUSTOMER-DRIVEN DESIGN

BASIC UTILITY VEHICLE

Volkswagen was once hailed as the car of the people. However, this proclamation did and does not take into account that more than half of the world’s population have transportation needs that cannot be met by a car that is designed primarily for daily commutes on paved roads.

In 2000, Will Austin, an American mechanical engineer with years of experience in automotive design and manufacturing, founded the Institute for Affordable Transportation. His primary product: an adaptable, affordable, multi-use machine that could be easily assembled or shipped and could handle varied and sometimes rugged terrain.

Austin’s Basic Utility Vehicle has since become a success in a number of developing nations, particularly in Tanzania. Each vehicle costs about $5,000, with financing easily available. The Institute for Affordable Transportation maintains active engagement with its customer bases to continuously improve and customize the vehicle for a wide range of needs. Currently the BUV is poised to enter the Zambian market.

EXPANSION AND COMPRESSION: 1ST LAW FIRE PISTONS

While most cars run on gasoline, diesel engines are more fuel efficient and diesel fuel has more energy than gasoline does. The diesel engine, however, is not the product of a new technology.

The fire piston was invented in southeast Asia several thousand years ago. The way a fire piston functions is quite simple and involves two basic parts: a rod and a cylinder. When the rod is inserted into the cylinder

and work is used to drive the rod forward, the result is a piston. When tinder is attached to the bottom of the rod, this pressure system can be used to start fires—and was, for a long, long time. In fact, long after the ancient invention of the fire piston, when Rudolf Diesel’s student, Carl

Von Linde, visited Pinang to give a lecture in the 1800s, he was gifted a special cigarette lighter that can only be described as a fire piston. When Professor Diesel saw him use the device, he applied the lighter’s principles to his work on internal combustion engines, and to much success.

While modern developments have greatly improved our lives, sometimes the answers to contemporary problems lie in the old days.

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Case studies allow students to put themselves in the middle of an interesting story that calls on them to think about a technical issue in a different way, tease out an opportunity from a set of circumstances, or analyze trends and ambiguous information to make a decision.

Often times, case studies are no more than lengthy word problems or focus on engineering failures. The engineering case studies developed by faculty are intentionally different. They are meant to inspire students’ curiosity, and provide context for challenging technical concepts taught in core engineering courses.

The case studies are written like magazine profiles, typically three pages long, and include teaching notes. They fall into three different categories:

LEAN: discussion-based and sometimes a homework problem (15 minutes of class time) CLASSIC: discussion questions and small group work prompts (50 minutes of class time) ACTIVE: a lab, project, hands-on activity, or other type of student-generated work

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Software Engineering and Computer Science

• Design impacting business models

(Instagram and Kiko)

Mechanical Engineering

• Customer-driven design (Basic Utility Vehicle)

• Expansion and compression/1st law

(Fire Pistons)

• Slip/tip, centroids (Sun King Brewery)

• Customer pain points (Touch N Brush)

• Laminar vs. turbulent flow (Reynolds)

• Number, casting/machining (TurboTap)

Electrical Engineering

• Electric sensors (Airbags)

• Color image analysis (Google Goggles)

Biomedical Engineering

• Illuminating blood vessels (Veinlite)

• Ethics of donor tissue (HeLa cells)

• Skin transplants (Dermagraft)

• Polymerization (Discovery of bone cement)

AVAILABLE CASES

(FOR USE IN YOUR CLASS)

Find the full stories:

engineeringunleashed.com/case-studies

A STEP-BY-STEP GUIDE TO BIOCOMPATIBILITY

“Excuse me, sir, but I think you have some

BIOCOMPATIBILITY TEACHING NOTES

Review the questions below to ask your students. In the process of answering these questions, they’ll need to cover the stages of free radical polymerization, as shown in the drawings:

aeroplane in your eye.”

• • •

• • •

Why is the bottle of liquid MMA brown?

How long will the reaction between PMMA and MMA take?

What happens physically to the properties of PMMA and MMA during polymerization?

What is a radio paci er?

How does the initiation reaction work? What’s the hydroquinone for?

ADDITIONAL QUESTIONS TO ASK:

• Mixing bone cement is an exothermic reaction. What considerations need to be taken as a result?

THANKS TO SIR HAROLD RIDLEY, M.D., WE CAN SAY THAT WITHOUT

A HINT OF ABSURDITY.

STEP ONE: Put a Plane in Your Eye. World War II was winding down, but Ridley’s commitment

to his country was just beginning. In Britain, Ridley was examining Royal Air Force pilots returning from duty. As an ophthalmologist, he noted that pilots whose planes had been hit, often had shrapnel in their eyes. Oddly, some of them weren’t experiencing adverse reactions to the debris. Speci cally, when it was shrapnel from the plastic canopies that had shattered and lodged in the eye. When the eye healed, it accepted the shrapnel into the organ.

What Ridley noticed confused him. The medical knowledge at the time stated that any foreign object implanted into

the body would cause some sort of adverse reaction.

For instance, a splinter in the hand could cause an

infection. However, these shards of plastic were causing

no in ammation or irritation after the initial trauma—a de nition of biocompatibility. The eye was especially thought of as an organ that would not tolerate foreign objects, but here Ridley had pilots cycling through his clinic, all with the same shrapnel in their eyes, causing no problems.

Ridley called up the plane manufacturers and ordered sheets of methyl methacrylate, the material used to create the plane canopies. If this plastic could be accepted by the eye, then surgeons could remove cataracts and replace them with intraocular lenses made of methyl methacrylate.

This hypothesis was not without controversy. Biocompatibility was a divisive topic, especially for the eye. No one had ever implanted a biomaterial before, and many prominent doctors thought that at some point the body would reject the foreign materials, leaving the patient in worse shape than before. Even though Ridley was able to ne-tune his methods in the 1960s, it wasn’t until the 1980s before his intraocular lens received FDA approval.

Today, over 7 million people a year get a little bit of plane in their eyes, combating a cataract diagnosis that at one point resulted in sure blindness.

STEP TWO: Mix Crushed Windows with a Carcinogen and Stick it on Your Bones.

PMMA—Poly(methyl methacrylate) is widely known as Plexiglass—the stu we use in windows and castings due

to its durability. That’s why the planes the Royal Air Force was ying—Spit res and Hurricanes—used the stu in its windows. When Ridley discovered PMMA’s biocompatibility and proved that biocompatible substances even existed, though, the medical world was excited to nd other uses for PMMA.

One use for PMMA that was discovered early on was bone cement. Surgeons were struggling with nding a substance that the body wouldn’t reject that would allow them to a x implants or repair bones, but would also be strong enough

to stand up to wear. In order to be able to shape the PMMA bone cement, it needed to be supplied as a powder and mixed with a liquid MMA monomer to catalyze the polymerization.

The catch is this: by itself, MMA is an irritant and a carcinogen. However, though free radical polymerization, MMA combines with PMMA to avoid the problems that MMA would cause on its own.

There are, of course other issues to consider with the use of PMMA. Students should consider the properties of the powder and liquid and the list of questions below and come to class ready to apply their knowledge of free radical polymerization to these ideas.

• What other applications do we use

•

What processing/ storing/transporting considerations need to be taken with bone cement, due to its properties?

What else could we apply biocompatibility to? What other problems could we solve now that we know about the intraocular lens and bone cement?

•

bone cement for?

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POWDER

• PMMA (Polymethyl Methacrylate) base

• ZrO2 or BaSO4 radio paci er

• Benzoyl Peroxide (initiator)

• Chlorophyll (dye)

LIQUID

• MMA (Methyl Methacrylate)

• •

•

Monomer

N-N-dimethyl-p- toluidine (DMPT)- Initiator

Benzoyl Peroxide: Reacts with DMPT to catalyze polymerization

Hydroquinone: Inhibitor