Engineering News 7669

Cloning opens new engineering opportunities

Newton, MA--In the rush to ban human cloning, legislators should not tie the hands of scientists (and engineers) engaged in cutting-edge genetic research, biotech industry officials warn. Clergy and moralists, however, say the government has every right to scrutinize the new technology and--if necessary--approve tough regulations on certain types of experimentation.

These convictions follow the announcement that scientists at Scotland's Roslin Institute have successfully cloned a sheep named Dolly. Shortly thereafter, scientists at the Oregon Regional Primate Research Center in Portland revealed that they had produced sibling rhesus monkeys from clone embryos in the technology's closest application to a species related to humans.

The announcements have sparked a nationwide debate about the procedure, prompting President Bill Clinton to call for a voluntary moratorium on any attempts to clone a human being. But what does all this mean for engineers? New employment opportunities, for one thing.

James Geraghty, president and CEO of Genzyme Transgenics, Framingham, MA, echoed the feelings of many professionals and politicians who addressed the subject of cloning following these outbursts. Agreeing that there is "no place for the cloning of human beings," Geraghty also notes that the medical benefits of new forms of genetic research, including transgenic technology--the transferring of genetic materials from one species to another--could be far reaching .

No matter what technology is employed, the bio-tech industry, although embryonic like some of its discoveries, is in a growth mode. For example, Massachusetts has the second highest concentration of biotech companies in the U.S., employing more than 16,000 people. Of this number, 3,706, or about 23%, are employed in research and development operations. Companies in this field need motors, pumps, sensors, and various materials, and therefore these technologies will drive many of the innovations that will come in the biotech industry in coming years.

On a national scale, U.S. demand for biotechnology products is forecast to in-crease over 20% annually to $20 billion in the year 2000, according to the Cleveland-based Freedonia Group in a study of the industry released late last year. Of this amount, bioengineered pharmaceuticals will account for more than $13 billion by the year 2000, up from $5.2 billion in 1995, while the demand for biotechnology-based research and diagnostic products will increase 12% a year to $4.2 billion in the year 2000.

In all, 1,287 companies, academic institutions, and hospital-affiliated enterprises are pursuing commercial bio-technology applications in the U.S. alone, according to an Ernst & Young report. These industry leaders currently employ 118,000 people, up 10,000 from the prior year; had sales totaling $10.8 billion in the 1996-97 fiscal year; have $83.3 billion in capital; and spent $7.8 billion on research and development.

Although no one appears to have any concrete figures from an employment perspective, engineers should reap some of the rewards from this growth. Among the engineers most in demand: mechanical, chemical, material, electrical, and process, according to industry sources.

"I spent several years selling process and capital equipment to the biotechnology and pharmaceutical industry in the San Francisco Bay area," says Randall Tedder, sales and accounts manager for Vitadata. His firm operates the Bio Online service that supports communications within the life sciences community on the Internet (http://bio.com). "A large proportion of my customers and contacts are engineers involved in process development, scale-up, and general-purpose mechanical engineering, as well as electrical engineering," Tedder continues. "Many companies have their own engineering staffs, but they also contract with outside engineering firms due to the large volume of work that needs to be done."

Thousands of companies supply equipment to the bio-tech industry and are employing thousands of engineers. Some of the key beneficiaries of biotech growth will be firms that make membrane filters, with sales growing 6 to 9% in 1996 from $2.1 billion in 1995, according to Delco Scientific Resources Inc., Albuquerque, NM. Capillary electrophoresis is another area slated for growth, with such companies as Hewlett-Packard, Perkin-Elmer, and Beckman playing prominent roles. And process separation technology firms should benefit as well, with a worldwide market for this equipment reaching about $800 million in 1996.

Money well spent. Some heavy R&D dollars went into the Scotland cloning project, where Keith Campbell, a cell biologist at the Roslin Institute, found the right "player" for his research--a sheep oocyte, or egg cell, containing special proteins that turn on genes. One can compare the finding to a CD's laser beam being able to skip around and pick any specific track to play.

The Roslin Institute scientists, nurtured by PPL Therapeutics plc of Edinburgh, wanted to genetically engineer sheep and cows so that their milk would contain human proteins. Not just any proteins, but those with medicinal uses.

Early this year, PPL threw a coming-out part for Rosie, a cow whose milk contains human alpha-lactalbumin. This protein has just about all the amino acids a newborn needs. The idea is to purify the protein from Rosie's milk and sell it in powdered form for premature babies who cannot nurse. Other companies are banking on cloning animals with human genetic sequences for everything from blood to heart-transplant applications.

PPL Research Director Alan Colman says that when using normal transgenic breeding, only 1 or 2 of every 10 sheep produce a sufficiently high level of the desired protein. But with cloning, he predicts, "they'd all be high-producing animals, and we'd have a production herd in the first generation."

The company is talking about a $1 billion market for its products early in the next decade. It hopes to clone genetically engineered animals that will produce a tissue "glue" for use in surgery and a drug for treating cystic fibrosis.

Genzyme Transgenics is raising goats whose milk contains a human anticlotting protein that can be used on heart-surgery patients. Another company, Alexion Pharmaceutical, New Haven, CT, is working on ways to get pigs to grow hearts and kidneys that won't be rejected in transplants. The program, called UniGraft, is a collaborative effort between Alexion and the United States Surgical Corp. to develop non-human organ products.

Rejection of non-human tissue is believed to occur in two stages, a rapid hyperacute phase extending over minutes, and a somewhat less rapid acute phase lasting for days to months. Alexion believes that hyperacute rejection is mediated by naturally occurring human antibodies found in transplant patients. In a double-barreled approach to the problem of hyperacute rejection, Alexion has under development genetically engineered non-human cells and organs that do not express the harmful carbohydrate antigen that acts as the binding site for naturally occurring human antibodies.

Still, what lies ahead for this intriguing technology remains somewhat foggy. There appears to be a potentially rewarding future for the firms that take the lead in bringing the technology to market--and a potential surge in engineering jobs. However, legislative human-cloning actions in Congress or state governments may make this a more limited opportunity.

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Surgeons and engineers get together with CAD

Warsaw, IN--Healthy bones and joints come in shapes and sizes perfectly tailored to their owners. Makers of orthopedic implants are forced by economics to offer a somewhat less complete line of replacement parts. Nevertheless, Zimmer Inc., a division of Bristol-Meyers Squibb, has endeavored to bring surgeons and engineers together to design hip implants with hundreds of possible configurations.

The company says this is a 10-fold increase over its previous product offerings. "In the past we would have different product lines for each category," relates David Feinstein, director of engineering technical services. "Now we are developing a unified product line encompassing many subtle variations, with common instrumentation for implantation."

Known internally as the Delta Project, the effort involves designing and manufacturing multiple configurations of hip implants drawing on the expertise of consulting surgeons on site. Feinstein says the surgeons were teamed with design and manufacturing engineers to incorporate anatomical data and CNC machining requirements early on in the product development cycle.

Anatomical structures are developed initially in Zimmer's ANADAT Anatomical Database. The system is based on CAT scans of human legs. Contoured wireframe geometry drawn with ANADAT's modeling functions are imported into Unigraphics from EDS/Unigraphics, Maryland Heights, MO. Engineers use the software to develop solid models of the implants.

Once the implant has been rendered as a solid model, Zimmer can use it to generate SLA files for rapid prototyping. Engineers also use photorealistic rendering functions to see the surface effects of modifications on designs. Once designs are fully validated, solid-model geometry is exported to Unigraphics CAM for NC programming.

"We often get substantial changes far downstream in the design process, changes that can have huge impacts on delivery times," Feinstein says. "The Delta Project has enabled us to react to changes very quickly, regenerating models, drawings, and CNC programs in Unigraphics."

Blood analyzer relies on level sensors

Plainville, CT--A next-generation immunoassay analyzer relies on a custom-designed set of liquid-level sensor assemblies to keep it running at its optimum. Under development by the Diagnostics division of Abbott Laboratories, it mixes chemical reagents with blood samples and performs multiple tests on more than 200 different blood specimens per hour, making it one of the fastest instruments of its kind. The analyzer relies on level sensors to warn operators when the reagent reservoirs are low, so testing continues uninterrupted.

Light photon analysis of the blood/reagent solutions within the instrument provide physicians with vital information on a patient's condition. Accuracy and testing speed are always important, but become critical in an operation where hundreds of tests are performed hourly.

The chemicals are delivered to the analyzer from reservoirs. It's critical that the reservoirs never run dry. Any air siphoned into the system invalidates all tests being run and necessitates expensive re-priming of the chemical reagents--not to mention requiring patients to have blood drawn for retesting. However, the chemical reagents are expensive, making it desirable to use as much of them as possible. Therein lies the challenge.

The machine's operation is generally automatic. Three bottles with three level sensors handle various siphoning applications. Two of the bottles are designed to be changed manually. The third bottle is refilled automatically from a reservoir with the refilling operation monitored by a liquid-level sensor.

After consulting with Gems Sensors (Plainville, CT), Abbott engineers selected float switches for their reliability, accuracy, and cost effectiveness. Gems suggested its LS-350 with small poly- sulfone-bodied switches. The devices use a magnet-equipped float that moves with the liquid level along the unit's stem and allows as many as four actuation levels. The magnetic field actuates a hermetically sealed, magnetic reed switch mounted in the stem.

To customize LS-350s for the new instrument, Gems' engineers combined a level sensor and draw tube to siphon the reagents up into the machine. The first two reservoirs use single-point-level LS-350 switches. As the float reaches a preset actuation level near the bottom, an alarm sounds to alert the tester that a specified number of tests remain.

The third reservoir requires three separate switch-actuation levels: high, low, and low-low. It is replenished from a fourth reservoir, and when the chemicals get to the low setting, an alarm alerts the operators that the refilling sequence has begun. However, should the chemicals get to the "low-low" level, the sensor signals the analyzer to shut down to protect the integrity of the rest of the blood samples.

Motor, control technology makes bone drilling less tedious

by John Lewis Northeast Technical Editor

Bartlett, TN--New motor and control technologies are helping surgical handpiece designers trim weight and improve balance. The result: safer procedures. For example, surgeons operating in the middle ear may drill for two hours to access the appropriate area. Mastoid-bone thickness, combined with the proximity of vital nerves, challenge both the skill and stamina of even the most accomplished surgeons.

"Many surgeons complain of hand fatigue," says Patrick Ireland, senior product development engineer for Bartlett, TN-based Smith & Nephew Inc., ENT Division. "Fatigue is undesirable because control is critical around such delicate structures. That's why one of our key constraints for the next-generation mastoid drill was to reduce weight and handpiece diameter."

Ireland chose Transicoil Inc. (Valley Forge, PA) to supply the motor/amplifier for a new mastoid drill design. Transicoil Design Engineer Bob Lazarski explains that regular sterilization requires that the motor withstand exposure to steam at 2 atmospheres and 300F. Making the motor robust enough for the autoclaving process meant using:

Mounting into one end of the handpiece, the motor couples to the main drive shaft. "Maintaining the burr at a constant speed of 40,000 rpm can generate a significant amount of heat," explains Lazarski. "To minimize velocity-related heat dissipation, we used proprietary materials in the motor's magnetic circuit."

Because the motor puts out 1 ounce-inch of torque, Ireland wanted to eliminate reaction torque in the handpiece. Scott Enright, Transicoil project engineer, explains the soft-start/dynamic-brake feature: "The circuitry gently ramps up to 40,000 rpm. Stopping options include coasting to a stop, or using the dynamic brake to stop in only a few revolutions."

As engineers integrate new motor and control technologies into handpiece designs, they offer patients added safety, while surgeons gain improved control, less fatigue, and greater accuracy.

Dual-head design images diverse patient types

Hoffman Estates, IL--All types of patients, including those restricted to wheelchairs or gurneys, can be easily accommodated with the E.CAM^TM emission imaging system from Siemens Medical Systems Nuclear Medicine Group. Dual variable-angle detector heads provide optimum imaging geometry and performance. Head position can be geared to body type and situation.

For bustling medical facilities, E.CAM is aimed at increasing imaging throughput, with minimal reimaging. "We received extensive customer input from around the world which resulted in a design that allows direct imaging of any patient," says Randy Weatherhead, Siemens marketing vice president.

The dual photomultiplier-tube-based digital detectors are mounted around a circular pallet-pass-through open gantry. Operators can tilt the detectors relative to the pallet axis, which also permits positioning the detectors at 90 degrees to the floor for imaging a subject standing or in a wheelchair. For conventional pass-through imaging, a 0.1-inch-thick pallet positions a patient close to the detectors. The overall design, claims Weatherhead,cuts part count by 30%, compared to other systems.

The first E.CAM was put into operation at Rush Presbyterian-St. Luke's Medical Center (Chicago, IL) last November. It is now used in up to 50 studies a day. Ernest Fordham, the center's nuclear medicine director, is impressed with the quality and uniformity of the images: "They're sharper and more detailed. With this kind of resolution and versatility we can use it on everything from small-organ imaging to whole body scans."

Software aids fight against cancer

New York--Using PDEase2D software from Macsyma Inc., Arlington, MA, Dr. Gene R. DiResta is studying the problems associated with delivering chemotherapy to solid tumors. The software analyzes data from functional and structural imaging modalities, including magnetic resonance imaging and X-ray computer tomography. DiResta's work is being done at The Nuclear Medicine Research Laboratory at Memorial Sloan Kettering Cancer Center.

PDEase2D, a front-end language, can model static and time-dependent problems involving partial differential equations using the finite-element method (FEM). By defining the mathematical portion and geometry of the problem, the FEM part is left to PDEase2D, which then creates, solves, and postprocesses the results.

With the help of PDEase2D, DiResta is modeling both the transport phenomena of chemotherapy into solid tumors and tumor-induced stress surrounding tissue.

Using the software to model the movement of drug tracers with a variety of distributed parameter models, DiResta is trying to predict drug distribution. He models human tissue as a porous medium. The model is completed using appropriate boundary conditions to represent normal tissue and necrotic regions, then further embellished with terms representing diffusion, convection, and reaction of drugs.

DiResta compares this model data to the measured distribution information from the images taken with the structural and functional imaging equipment. The combination of these images provides a picture of tumor morphology and metabolism, which serve as raw data for FEM models.

"Our objective is to 'image' a patient noninvasively before he or she receives chemotherapy," he explains. "In this way, we'll be able to give a tighter prediction of drug impact before subjecting the patient to unnecessary cost and discomfort."

In the future, DiResta will use PDEase-2D to do parameter estimation of models. "The clinician is looking for a parameter relating transport impedance to therapeutic outcome," he says.

Cell-processing system perks with polycarbonate

Mountain View, CA--Stem-cell enrichment can mean the difference between life and death for people suffering from various blood diseases. A new closed centrifugation system for processing cells from Activated Cell Therapy (ACT) Inc. permits minimal nonspecific cell loss--a typical problem in cell processing that could jeopardize the desired clinical outcome.

In designing the centrifugation system for the disposable ACT-300, which processes hematopoietic progenitor (CD34) cells, materials played a key role. Like the centrifuge, the designers quickly separated the strong from the weak.The winner: Makrolon(R) Rx-2530 polycarbonate (PC) resin from the Bayer Corp.'s Polymers Div., Pittsburgh.

The radiation-stabilized PC features a balance between processibility and good chemical resistance. It also reduces initial yellowing upon irradiation by 60%, while providing rapid color equilibrium, according to Peter Van Vlasselaer, director of research and development for ACT.

"We needed a biocompatible material that could withstand a centrifugal force of 850G for 30 minutes and would remain transparent during sterilization," Van Vlasselaer explains. "The PC was much stronger than polystyrene and less expensive than polysulfone, the two other materials we considered."

The ACT-300 system consists of three PC components: a base (cup), cap, and support piece. The cap is ultrasonically welded or glue-bonded to the base, and the disk-shaped support leaves a space below the bottom floor for cell collection. A silicone insert, which rests on top of the support disk, acts as a slide and divides the centrifugation device into an upper and lower compartment.

The sterile disposable system, compatible with most centrifuges, is filled with ACT's proprietary buoyant density solution. A white blood cell preparation is overlaid on top of this solution and the device centrifuged. During the centrifugal process, the heavier cells move downward and hit the slope of the silicone disk. They then roll into the hole and end up in the lower compartment.

Lower-density cells, such as CD34 cells, float and are poured off through sterile transfer sets. Because of its design, the ACT-300 system permits both a high volume reduction and a high yield of an enriched cell preparation.

The ACT 300 device addresses specific technical and clinical issues related to cell processing. The primary clinical performance depends on the specific characteristics of the buoyant density solution added to the ACT 300 centrifugation container. One goal of the design: to complement the process of buoyant density solution with sample--without compromising clinical performance.

The design meets this goal as follows:

Not only does the system provide a more sterile product, but it increases the yield of the patient's valuable cells.

Materials improve medical products

Wilmington, DE--DuPont Engineering Polymers is providing solutions for tough medical problems. A component made with DuPont Hytrel(R) polyester elastomer lets users of the Harvey Elite^TM Stethoscope adjust earpiece tension and angle for optimum comfort and acoustic fit. And the company's Zytel(R) nylon is improving durability of wheelchair wheels.

The stethoscope component is a U-shaped nested leaf spring molded with nine metal inserts: two tubular earpieces at the sides, three metal leaf springs in its lower portion, and four retainer clips. This arrangement allows adjustment of ear tube tension by spreading or squeezing the lower portion of the elastomer-encapsulated component. Angular adjustments are made by rotating the ear tube.

Alliance Carolina, Arden, NC, injection molds the tensioning component from Hytrel for Tycos Instruments Inc., also of Arden. Until recently, the molder was using thermoplastic polyurethane, but was encountering several recurring defects and an unacceptable reject rate caused by the TPU's inconsistent melt flow, according to Jim Ellis, molding manager at Alliance Carolina. "Switching to Hytrel has eliminated molding problems and sharply reduced costs," notes Ellis.

For those who depend on battery-powered wheelchairs and scooters, wheels designed with DuPont Zytel(R) could reduce breakdowns and maintenance. The new Bead Lok^TM wheels from Skyway, Redding, CA, provide four advantages over traditional metal wheels: less risk of tire roll-off, lower rolling resistance, more resistance to impact damage, and lower cost.

The structural wheel of the Bead Lok consists of two matching parts injection molded from Zytel that are bolted together. An integrally molded bead in each half locks into a mating groove in the wheel's solid polyurethane tire as the wheel halves are bolted together.

The Bead Lok wheel is engineered to stand up to conditions such as running on tough pavement. "Thanks to the elastic properties of Zytel, our wheels regain their original shape when subjected to sharp impact loads that cause permanent deformation of metal wheels," says Ken Coster, Skyway president.

Hubble technology aids medical imaging

Greenbelt, MD--The Hubble Space Telescope program has taken it on the chin more than once, most recently for the failure of a component of the newly installed infrared imaging system. However, NASA officials are quick to point out that much of the technology developed for their expensive eye in the sky has spun out into people's everyday lives--sometimes with profound results.

A prime example is the charged-coupled device (CCD) system developed specifically for Hubble that is now used to enable less-invasive breast biopsy procedures. NASA's Goddard Spaceflight Center determined early on that existing CCD technology--which converts light directly into digital images using silicon chips--did not possess sufficient low-light resolution for the orbital observatory. Goddard contracted with Scientific Imaging Technologies Inc., Beaverton, OR, to develop a CCD system that doubles the density of photoreceptors per chip.

The result was the SITe SI-003A scientific-grade CCD Imager. The component is thinned and back-lit to improve incident light conversion. Electrodes connecting the chip to the rest of the system come out one side of the chip rather than out the back, so chips can be placed back-to-back. In addition, since only one edge has leads running out, chips can be packed tightly together.

"More photoreceptors mean better low-light performance," says Don Vargo, senior technology analyst with NASA Goddard. While this is just the thing for imaging faint objects such as distant galaxies, it is also useful for imaging nearly any object in low-light environments. "This realization is what inspired us to look for applications in the medical field."

The technology-transfer effort led to LORAD, a subsidiary of Trex Medical Corp. The company incorporates the SITe CCD Imager as part of its StereoGuide Breast Biopsy System. The device, delivered by a catheter inserted through a small incision, can be used to image suspicious breast tissue. The images provide doctors with a clearer picture of the tissue's nature than do X-rays. The stereo images can also be used to help the doctor guide a biopsy needle to the target area, reducing trauma.

Hundreds of thousands of women undergo breast biopsies each year. A biopsy in effect is a little operation, and the procedures often incur a significant loss of tissue and produce permanent scarring. The LORAD StereoGuide Breast Biopsy System produces less patient discomfort, trauma, and scarring than conventional biopsies. In addition, the procedure can be performed on a patient under local anesthesia.

Thinned, back-illuminated CCDs typically have a 50 to 150% higher quantum efficiency rating than front-illuminated devices, which can be found in commercial electronics, such as video cameras. The higher-performance back-lit devices are also finding application in nuclear and gamma imaging, protein crystallography, optical microscopy, and specialized aerospace tasks.

Step motors help drive cataract-surgery system

Salt Lake City, UT--A new cataract surgery system designed by ZEVEX, a Salt Lake City contract design and manufacturing firm, relies on step motors to handle critical fluid-delivery chores. Selected over dc servos, the steppers--provided by Oriental Motor (Torrance, CA)--offered an easy-to-implement, reliable, low-cost, low-noise means to drive both actuators and pumps via the industrial Intel Pentium-based PC engineers were already placing on board.

"We went to full computer control with this system," says David Blaine, senior electronic engineer at ZEVEX. "It seemed logical to keep everything digital and go with step motors rather than servos."

Called the Precisionist Thirty Thousand, the phacoemulsifier was developed by ZEVEX for its OEM customer, Paradigm Medical. "What makes it unique is that it offers the standard ultrasonic technique and--for clinical-trial use only right now--a second laser-based method patented by Paradigm," says Dean Constantine, president of ZEVEX.

Phacoemulsification, by either ultrasound or laser, is the process of breaking up a diseased lens into small pieces, and then aspirating the pieces from the eye. This is where the step motors do their job.

One, a model PK266-01A, powers a vertically oriented pole that holds a bottle of balanced saline solution which feeds into the eye via gravity. The motor drives a ball screw that moves the pole at a safe 4.5 cm/sec and is controlled by the doctor with a foot pedal. To date, the pole has been cycled in tests more than 35,000 times. These tests amount to the equivalent of more than 20 years normal operation.

A second step motor, a model PK264-01A, drives a peristaltic pump used to aspirate the tissue and fluid from the eye back through the hand piece and into a bag.

Both motors team to keep the eye irrigated during surgery. "Getting and maintaining the correct flow rate is very important," Blaine explains. "The doctor uses the back pressure to keep the shape of the eye and prevent it from collapsing."

Blaine chose Oriental Motor steppers for their smoothness and resonance. "The toughest thing was preventing noise and resonance," he says. "The side panels make good sounding boards, and it helps if the motor doesn't put out much noise and vibration to begin with."

Plastics solve surgical smoke problem

Phoenix, AZ--Electrocautery equipment has replaced the traditional scalpel in about 80% of surgeries. Why? It seals small blood vessels as it cuts, resulting in a clearer operating area, a smaller and more readily healed incision, and a reduced chance of infection.

The procedure also has its problems. Smoke created by the instrument's high temperatures had a pungent "sick tissue" smell and could carry dangerous bacteria and viruses--including HIV.

"This smoke is dangerous," reports Ioan Cosmescu, president and CEO of I.C. Medical Inc. (ICM), developer and manufacturer of the PenEvac electrocautery scalpel system. His patent-pending disposable device can be telescopically adjusted to lengthen the electrode and locates the smoke evacuation nozzle where the smoke is created during surgical procedures.

For his system, Cosmescu selected three grades of K-Resin(R) styrene-butadiene copolymer (SBC) to injection mold Pen-Evac components. The material, supplied by Phillips Chemical Co., Bartlesville, OK, provides the strength and flexibility needed to make the PenEvac a streamlined product, according to Cosmescu.

The firm's electrocautery surgical system includes the multifunctional PenEvac handpiece and a suction/irrigation controller. The handpiece consists of white, translucent K-Resin RK52 copolymer. Phillips developed the SBC grade to bridge the economic and performance gap between acrylontrile-butadiene-styrene (ABS) and high-gloss, high-impact polystyrene (HIPS).

ICM first switched to the SBC to solve a problem in the shroud that holds an electrosurgical pencil and suctions away smoke and particulates. Cosmescu's design created a single, slim instrument that effectively places the smoke evacuator pick-up nozzle where electrocauterization creates the smelly, potentially harmful smoke.

Originally made from polycarbonate (PC), Cosmescu had to find a replacement material that would reduce the diameter of the shroud. Doctors complained that holding the large-diameter part was uncomfortable during a long operation. The bulky size of the shroud was due to the 0.060-inch-thick walls needed to keep the PC from breaking. Thinner walls would fracture. With K-Resin SBC, ICM could reduce the wall thickness to 0.030 inch and still maintain structural integrity.

However, another problem bothered Jim Busche, ICM's disposable-products manager and former custom-molding shop owner. He was concerned with how the glued weld line performed. The shroud, at 7 inches long with a 2-inch circumference, must be molded in two pieces due to resin-flow time. He reports that the K-Resin SBC also solved the glue weld-line problems found with the PC.

"The shroud was really our first commercial product," explains Cosmescu. "Along with our nozzle tip, it allows for the full use of a vortex to evacuate the smoke and eliminate carcinogenic char."

Following the success of the shroud, Cosmescu developed his own complete system. The PenEvac "scalpel" attaches to the ICM Crystal Vision Automatic Smoke Evacuation system through an electronic cable and a suction tube. It allows a surgeon to hold the electrocautery pencil and the smoke-evacuation unit in one hand.

Label keeps time on electrode use

Inglewood, CA--When Cardiotronics (Carlsbad, CA) developed a timekeeping device for its cardiac stimulation electrodes, the company turned to Acutek for help with the construction.

The Time Keeper is a "label" added to the Cardiotronics line of electrodes, which are used for defibrillation, external pacing, and synchronized cardioversion. The label indicates when the electrode pads need to be changed--important because the pads are to remain on no longer than 24 hours.

After a medical attendant applies the label to the electrode pads, he or she pulls a folded release liner out of the label, bringing an adhesive into contact with the time-release ink. An activator in the adhesive causes the ink to permeate the face stock and rise to the surface of the label.

When the 24-hour time-release process is complete, a "Change Pad" message appears in the exact same color as a pre-printed message written across the bottom of the label. The color matching enables attendants to judge time passage and determine whether the electrode pads are fresh or have been on too long.

Construction of the label involves a multilayer lamination process with multiple stations printing at the same time. "Coordinating the timing of the process was the complicated part," says Michael Muchin, R&D director at Acutek.

The label comprises three parts: the top face stock, the folded release liner, and the adhesive-backed base paper that adheres to the pad.

Acutek applies the time-release ink to the front upper portion of the base paper. The lower portion is joined to the back of the face stock. The top half of the back of the face stock is coated with activator. A release liner is folded between the upper areas of the base paper and the back of the face stock. The liner protects the top layer's activator/adhesive from the time-release ink on the bottom layer. Once the adhesive and ink come into contact, activation starts immediately.

"The project was complex because it involved folding the release liner and printing in three different areas," says Jim Perrault, R&D director at Cardiotronics, "but Acutek lived up to its reputation of being a good quality converter."

The time-sensitive label technology was originally developed by Temtec (Suffern, NY) for security badges. The Time Keeper is the first medical application of the technology.

Plastic models train keyhole surgeons

Rustington, UK--Medical teaching models made by Educational and Scientific Products Ltd. (ESP) have a life-like resemblance to human skin, muscle, ligaments, and bones. However, the models are 100% polyurethane.

A knee, marketed by Hillway Surgery Ltd. to train surgeons in keyhole surgery, typifies how realistic these models are. "We use a variety of soft polyurethanes and process them under different conditions to obtain the physical properties that al-most exactly match the real thing," explains Jane Seamer, an ESP director.

The knee is a full-size replica, with precision-molded bones connected with ligaments and cartilage. A thick layer of red muscle covers these parts, and over that goes a layer of pink skin. All the parts are produced using polyurethanes sup-plied by Hyperlast Ltd., Cheshire, UK.

The knee can be "operated" on as surgeons practice cutting and tying ligaments on a "patient" with exactly the right feel--but no feelings. After use, the knee can be disassembled and the cut ligaments replaced.

"The polymer we use for the muscle has a great ad-vantage as it effectively heals," Seamer adds. "The cut surfaces can be pushed together and they adhere very well. Even so, eventually the muscle and the skin need replacing. Like the ligaments, we supply these as replacement parts."

Perhaps the best known product from ESP's extensive product line is the full-size skeleton. "It's based on the real thing," says Seamer, "which we use for casting polyurethane molds. These, in turn, are used for casting the whole polyurethane bone. For this we use a polymer that is extremely hard, just like the real thing. Previously, the rigid parts were molded in acrylics, but polyurethanes are easier, safer, and better substitutes."

Again, any parts in the skeleton are easily replaced, "but we also run a repair service," Seamer adds. "Once more we find the polyurethane materials ideal, as they are easy to repair."

Software improves pipette design

Reno, NV--In designing its next generation of pipette products, Hamilton Co. wanted to address the strain and fatigue caused by repetitive pipette use. To this end, the company enlisted the help of two design firms, Lunar and Alchemy, and Studio software from Alias/Wavefront (Toronto).

Lunar developed the initial concept, focusing on precision and ergonomics, and then turned to Alchemy to further develop the pipette.

Alchemy used the Studio package to create ergonomically contoured shapes formed to fit a range of hand shapes and sizes. For example, the pipette's plunger button slopes to the thumb, and its flared hilt cradles the fingers, maximizing comfort and allowing relaxed control over the pipette.

With the sculptural aspects of the design complete, designers used Studio's ray-tracing capabilities to explore textural and material qualities. Displacement maps were applied to the surfaces to visualize different textures. Rendering capabilities enabled the design team to demonstrate material ideas too expensive to build as hard-model prototypes.

Though easily illustrated with procedural shaders, the dimple pattern in the pippette's grip was not easily modeled. To bypass this barrier, Alchemy set up a scaffolding of curves, normal to the surface, to help locate each hemisphere position at a precise depth within the surface. Designers then used Studio's animation code to modulate the degree of nonproportional scaling along the pipette's length.

This combination of techniques provided the flexibility to quickly dial in different depths and shapes. Several permutations were built and exported to Pro/ENGINEER for tool draft analysis.

Stereolithography prototypes were created, and design variations implemented. After designers calculated an updated set of renderings, they programmed configuration variations and developed a metered, color-coded language.

According to the Alchemy designers, the overall flexibility of Alias Studio provided superior visualization and surface refinement for the project.

Sensor detects life-threatening heart signals

by John Lewis Northeast Technical Editor

Bedford, MA--Research, sponsored by Cambridge Heart Inc. is underway to determine if T-wave alternans (TWAs)--beat-to-beat variations in electrocardiogram T-waves--are useful for assessing arrhythmic risk. If proven useful, it may be possible to identify high-risk patients during a standard stress test using new non-invasive cardiac sensor technology.

There are 4.7 million patients suffering congestive heart failure (CHF) and an additional 400,000 new cases per year. These patients have a sudden death rate 6 to 9 times that of the general population.

A recent Multicenter Automatic Defibrillator Implantation Trial study confirmed in patients with CHF that implantable defibrillators reduce mortality in high-risk patients. "Identifying high-risk patients frequently requires an invasive electrophysiology study," ex-plains Tom Hennessey, Cambridge Heart's CFO and VP of operations.

TWAs are difficult to measure during active stress testing. "Near-field signals such as noise from moving muscles and artifacts interfere with the heart's signal. This makes measuring TWAs at microvolt levels extremely challenging," notes Hennessey.

"Our high-resolution electrode technology filters near-field noise and artifacts, and amplifies the heart's signal," explains Hennessey. Cranston, RI-based Poly-Flex Circuits manufactures the flexible circuits used in Cambridge Heart's new electrode.

The design, based on Cambridge Heart's pioneering work, was issued U.S. patent No. 5,570,969 late last year. The patent covers an improved method for assessing myocardial electrical stability using TWA measurements. The firm will use research results for its 510(k) submission to the FDA, expected this summer.

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