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Articles from 2001 In July


Sensors Shrink in Size

Originally Published MPMN July/August 2001

Product Update

Sensors Shrink in Size

Products benefit from increased sensitivity and resistance to interference.

Many medical devices must be able to accurately assess the conditions of their surrounding environments to function properly. To accomplish this important task, design engineers often incorporate any of a number of different sensors. In this section, several recent developments in sensor technology, including ultrasensitive superconducting magnetic sensors and a miniature motion tracker, are discussed that can help to ensure that your products function as accurately as possible.

SQUIDs provide detailed detection in magnetic monitoring systems

According to a report from Frost & Sullivan, SQUIDs may be what are needed to build better magnetocardiography (MCG) and magnetoencephalography (MEG) systems. Not multilimbed aquatic creatures, SQUIDs are the extremely sensitive magnetic sensors designated by an acronym that stands for superconducting quantum interference device. These sensors, also referred to as cryogenic magnetometers, consist of a superconducting ring with one or two weak switching points. The versatile devices can measure most physical parameters that produce a form of magnetic flux as small as 10-10G including magnetic fields, magnetic susceptibility, and electric current or voltage. A typical anistropic magnetoresistive sensor can only detect fields as small as 10-5 G. SQUID sensors work at cryogenic temperatures and come in two varieties: low temperature and high temperature. Low-temperature SQUIDs become superconductive at temperatures of –459°F, high-temperature units at –280°F.

While many applications could potentially benefit from this advanced technology, MCG and MEG systems have already started to profit from SQUID sensors. These magnetic monitoring systems use the sensors' high sensitivity to detect the small biomagnetic fields that accompany brain or heart diseases and muscle activity. Unlike CT, MRI, or other imaging systems that can perform similar tasks, SQUID systems offer the benefit of real-time functional imaging. Due to a variety of special concerns, fetal magnetic monitoring particularly stand to gain from SQUID technology. Superconducting magnetometers are noninvasive and thus allow the examination of fetal development at an earlier stage than other systems. "PET and MRI systems require radioactive isotopes or generate high energy fields, both of which can damage developing fetuses," says research analyst Daniela Carrillo. "SQUID systems, on the other hand, are passive devices that allow for safe monitoring at even early stages of development." According to the Frost & Sullivan report, the high temporal resolution of a SQUID system allows for a more accurate beat-to-beat representation of fetal heart rate than cardiotopography units. Though still in development, CTF Systems Inc. has constructed the first fetal MEG unit to use SQUID technology. The machine incorporates 151 sensors and has rendered promising preliminary results.

Magnetic motion tracker uses small sensor

A real-time magnetic motion tracker for medical and simulation applications uses a miniature sensor that allows precise navigation and guidance within the human body. The miniBIRD Model 500 tracking system from Ascension Technology Corp. includes an encapsulated sensor that measures just 10 x 5 x 5 mm. Designed for inclusion in laparoscopes, endoscopes, and probes, the sensor tracks position and orientation with six degrees of freedom. The sensor's signals pass through the body without attenuation and do not experience line-of-sight interference whether the unit is used internally or externally. "Because it uses pulsed dc technology, the magnetic sensor can be used in the presence of metals commonly found in clinical settings," says medical marketing manager Chris Perrera. Clinicians can use the sensor to perform computer-aided surgery, medical training simulations, biomechanical studies, and 3-D reconstruction of 2-D ultrasound images. Multiple sensors can work in combination to track multiple instruments and to provide differential readings of anatomical structures. An interface allows the sensor to connect to most host computers. A larger model, the miniBIRD Model 800, is also available with sensor dimensions of 18 x 8 x 8 mm.

Pressure transmitter links to process valves to form control loop

A programmable pressure sensor connects directly to process valves from most manufacturers to create a local intelligent control loop that reduces total system costs. With built-in intelligence and power systems, the Type 8326 pressure transmitter from Burkert-USA works independently of a PLC to complete a loop that the manufacturer estimates can reduce costs by as much as 35%. The transducer converts pressure into a proportional 4–20-mA output signal that is transmitted to the control valve, which adjusts its position accordingly. But this sensor has several other unique features. "The Type 8326 can simulate pressure outputs using real electrical signals to make sure the rest of the system is working correctly," says VP of marketing Andy Harris. "It can also be calibrated locally to reduce maintenance costs."

Accurate to ±0.15%, the Type 8326 sensor is suited for monitoring fluid pressure, fluid level, and pump and filter functions in pipes, technical equipment, and tanks. Standard pressure measurement spans 0–580 psi, but a turndown ratio of up to 1:20 allows the unit to measure a maximum pressure of 14,500 psi. The component is made of polybutylene terephthalate with stainless-steel wetted parts, making it suitable for use with fluids ranging in temperature from –22° to 221°F. Capable of storing up to 32 hydrostatic points via an optional LCD display, the sensor also has the capability to perform tank linearization. A range of fitting options allow the component to installed in new and existing systems. The sensor is available pretested and ready to install.

Cylindrical proximity sensors detect metallic particles

Suited for detecting metallic particles, miniature cylindrical proximity sensors from Altech Corp. are available with diameters of 3, 4, 5, or 6.5 mm. According to product manager Gil Yanishevsky, these products "are much smaller than other cylindrical sensors on the market, which typically have diameters of 12 to 18 mm." The sturdy sensors operate on a current of 10–30 V and have a maximum output of 200 mA. Frequency response attains 5000 Hz and acceptable operating temperatures span –25° to 70°C. The 3- and 4-mm units are 22 mm long, while the 5- and 6.5-mm units are available in a variety of lengths. The IP 67–protected sensors are constructed of stainless steel or nickel-plated brass. Most models are available with a choice of a fixed-cable or quick-disconnect outputs. All components feature an LED target indicator and can connect to a PLC. Typical applications include automated assembly and packaging lines. The sensors are CE marked and manufactured at an ISO 9001–registered facility.

Hall effect sensor works as switch

A Hall effect sensor from Micropac Industries Inc. functions as a switch that is activated by magnetic fields. In the presence of a sufficiently strong south pole field, the Mii P/N 65016 sensor turns to its On position. A corresponding north pole field resets the sensor to its Off configuration. The component is packaged in a hermetically sealed three-pin ceramic housing, making it suitable for harsh environments. An internal chopper-stabilized amplifier eliminates the input offset voltages normally associated with bipolar devices. This unique construction significantly improves operating point stability. Available manufactured to a variety of standards, the sensor can be included on motor controls, industrial switches, power supplies, and test equipment.

Level switch works in shallow tanks

A liquid level switch for high-volume applications can be used in shallow tanks and restricted areas. Constructed with polypropylene wetted materials rated for potable water systems, the LS-2 switch from Gems Sensors Inc. is 2 in. long and 1 in. in diameter. The device withstands pressures up to 150 PSIG and temperatures of –40° to 210°F. Available with M12 or 1/8-in. NPT mounting options, the switch has a fluted stem that prevents the formation of mineral deposits. Other features include 6-in. lead wires and a 10-VA switch. The unit's solid polypropylene float can be used in both water and chemicals with specific gravities as low as 0.85.

Zachary Turke

Copyright ©2001 Medical Product Manufacturing News

Sensing Dissension: Alternative Oxygen Sensor Technologies Presented at German Expo

Originally Published MPMN July/August 2001

INDUSTRY NEWS

Sensing Dissension: Alternative Oxygen Sensor Technologies Presented at German Expo

Electrochemical or paramagnetic? That was the question for attendees sourcing medical oxygen sensors at Sensor 2001 in Nürnberg, Germany. Two UK companies chose this showcase for sensor technology, which is held every two years in the spring, to present their oxygen sensors that employ alternative methods to achieve similar clinical outcomes.

Because they use a nondepleting technology, paramagnetic oxygen sensors from Servomex Group Ltd. are described as a permanent, safe solution for intensive-care applications.

Paramagnetic sensors use a nondepleting technology that allows them to operate for the life of the host device. This longevity has come at a steep cost... until now. The Paracube, developed by Servomex Group Ltd. (Crowborough, E Sussex, UK; www.servomex.com) for use in ventilators and neonatal incubators, reportedly narrows the price gap. The firm contends that the true cost of the component will be less than that of an electrochemical sensor when the cost is calculated over a 5-year period.

"The Paracube is extremely reliable," says Jörgen de Vos, business manager Europe, who represented the company at the show. "Electrochemical cells have a finite life and need to be calibrated daily," he says, whereas the Paracube can operate reliably for months without calibration. Unlike other paramagnetic sensors, this digital device has no feedback system, he adds. "A coil is wrapped around the dumbbell [two connected nitrogen-filled glass spheres] to make a dc motor. When oxygen is introduced, the coil oscillates, and this oscillation is a measurable representation of oxygen." Other advantages of the technology include a fast response time, high accuracy, and minimal maintenance requirements.

De Vos does add a caveat: the sensor is not suited for mobile systems. "It's not an issue if it's part of a device that is being wheeled around the hospital, but you wouldn't want to integrate the Paracube into a system used in ambulances, for example."

A fast-response electrochemical sensor by City Technology Ltd. measures oxygen delivery levels in incubators.

John Warburton, business development manager at City Technology Ltd. (Portsmouth, Hants, UK), acknowledges the reliability of paramagnetic sensors, but he wonders if they aren't an overengineered solution. He was at the show to present his company's new In-Q-OX O2 MediceL fast-response electrochemical oxygen sensor for infant incubators.

"Electrochemical sensors are less expensive than paramagnetic sensors," he noted, "and they are less fragile, because they have no moving parts." The sensors require no power to operate, making them suitable for integration into battery-powered transport incubators, and they withstand temperatures ranging from –20° to 50°C. In addition, the In-Q-OX has a T90 response time of <5 seconds, notes Warburton, "and it has a 2-year operating life in 50% oxygen, which equals 4 years in ambient oxygen." The sensor can operate in a range of 0–99% relative humidity.

The company also presented its NO sensors, which have been approved by FDA for use in the treatment of neonates with hypoxic respiratory failure, more commonly known as blue baby syndrome. "Nitric oxide at high levels is toxic," explains sales executive Teresa Standen, "but at low levels it promotes breathing." The MNO-1 and MNO-2 sensors are not affected by the presence of agent gases or N2O. They feature a <10 second T90 response time and temperature compensation, and are unaffected by operation in 100% oxygen.

Compact Pressure Sensor Is SMT Compatible

Also exhibiting at the show, Honeywell Sensing & Control (Freeport, IL; www.honeywell.com/sensing) previewed a new low-cost pressure sensor that conforms to the patterns of a DIP package and supports a range of sensing applications associated with medical devices. The 20PC sensor offers temperature-compensated circuitry in a compact package with surface mount technology (SMT) capability. "Its uniqueness resides in its size," says John Smith-Malzfeldt, marketing manager for Europe. The SMT profile saves critical board space, he notes, "and the sensor can withstand the flow solder process." A Wheatstone bridge construction, silicon piezoresistive technology, and ratiometric output ensure application flexibility and ease of manufacture. Applications include oxygen conservers, infusion pumps, blood glucose systems, and related devices.

A global presence in environmental measurement products and related industrial applications, Vaisala Oy (Helsinki, Finland; www.vaisala.com) previewed its portable dew-point analysis instrument at Sensor 2001, prior to the product's official summer launch. Of particular interest, according to product manager Jan Grönblad, is Vaisala's use of a polymer sensor in the DM70 in lieu of metal oxide, which has been the industry standard. "Metal oxide presents long-term stability problems when it's used to measure dry process gases with high humidity," says Grönblad. "Metal oxide decays when it is exposed to liquid water." The handheld probe also reacts very quickly, whereas metal oxide can take some time to stabilize, he adds.

The company will also be introducing a probe to measure CO2 that plugs into the modular device. The unit can be fitted with either probe, or both probes can be inserted to conduct simultaneous dew-point and CO2 readings. The instrument has applications in a range of process industries where moisture can be a contaminant.

Norbert Sparrow

Thermoplastic Earns Certification for Medical Products

Thermoplastic Earns Certification for Medical Products

A medical-grade elastomer from Thermoplastic Rubber Systems Inc. can be extruded and injection or blow molded.

A new elastomer from Thermoplastic Rubber Systems Inc. (Shirley, MA; www.trstpe.com) has earned a USP Class VI certificate of compliance for use in medical applications. The NexPrene 1200 series material is a vulcanized alloy made from ethylene-propylene-diene-monomer and polypropylene that offers several benefits over existing thermoset rubbers. "Because it is a thermoplastic," explains president Jonas Angus, "NexPrene 1200 can be extruded and injection or blow molded. Traditional materials are not amenable to these processes." Jonas also cites increased design flexibility and tolerance of gamma and E-beam sterilization as benefits. NexPrene 1200 is available in natural colors or in black with hardnesses ranging from 45 Shore A to 50 Shore D. The material tolerates high heat and is resistant to oil, making it suitable for use in gaskets, tubing, diaphragms, and valves.

Zachary Turke


Showroom Seeks to Energize Interest in Electric Molding Machines

Showroom Seeks to Energize Interest in Electric Molding Machines

This all-electric injection molding machine from Milacron Inc. is among the units the company will demonstrate at its new Energy Resource Center.

A manufacturer believes that all-electric injection molding machines are the solution for companies feeling the effects of the rising cost of power. To help convince others, Milacron Inc. (Batavia, OH; www.milacron.com) has established a showroom to demonstrate these machines, which they speculate could save the nation up to 8.9 million MWh annually. Located in Cincinnati, the Energy Resource Center will feature a variety of the molders for first-hand inspection, but the showroom is not just for molding personnel. Milacron is also directing its savings message to corporate management, financial executives, facility designers, and energy brokers. According to the company, electric molders are two to four times more efficient than their hydraulic counterparts. "A switch to all-electric injection machines could save an estimated 700,000 MW of power and $42 million in energy annually in California alone," says vp of technology Barr Klaus. Electric machines can offer these savings because they only consume electricity when doing actual work. Hydraulic molders, on the other hand, use energy even when idling.

Zachary Turke

IBA Harmonizes Quality Systems, Introduces On-Line Audits

IBA Harmonizes Quality Systems, Introduces On-Line Audits

Implemented in its North American facilities in January, the harmonization of quality systems at IBA's European operations will be completed in 2002.

No one can accuse IBA (Chicago; www.iba-worldwide.com) of thinking small. The company's relentless growth strategy—it recently doubled EtO sterilization capacity for medical devices at its Belgium facility—and purchase of SteriGenics and Griffith Micro Science in 1999 has catapulted the firm into the ranks of the world's leading suppliers of most sterilization methodologies and services. Operating 47 sites in 12 countries, IBA claims to have a 34% market share in medical device sterilization. Lisa Foster, vice president of corporate quality assurance for IBA North America, has set herself the task of folding the company's far-flung operations into a cohesive one-stop shop for sterilization services. She views IBA's efforts to harmonize quality systems at its worldwide facilities and to enable on-line audits as significant steps in that direction.

Harmonization of quality systems was a priority item for Foster when she was plucked from SteriGenics and appointed vice president in 1999. "We had standardized QS at SteriGenics sites throughout the world since 1992," says Foster, noting that it was a valuable tool for a contract sterilizer processing the same products at facilities in different states and countries. The SteriGenics document served as a template, but it required extensive rewriting to incorporate ISO 9000:2000.

"The new ISO standard is very different from the previous one, even when it comes to numbering the elements, and we had to organize our policy manual in the same format," says Foster. "And ISO 9000: 2000 is very focused on monitoring customer satisfaction. Which is not to say that we weren't already doing that, but now we had to establish procedures [that complied with the standard]."

The document, which was implemented in January at facilities in North America and Thailand, contains a policy manual that itemizes QS procedures common to all sterilization methodologies, and process procedures that detail validation and regulation requirements relevant to a specific technology and business unit. The framework draft is based on medical sterilization processes "because they are the most stringent," says Foster. "Then, we either removed or added [clauses] as necessary." The harmonization effort has been enthusiastically received by IBA's larger North American clients, whose products are processed at multiple facilities, but it also benefits the smaller customers, according to Foster.

"It has certainly been a selling point for the big customers, who appreciate that they can walk into any North American IBA facility and use the same form. But even if you're just using facilities in Corona and Hayward [CA], for example, you can write one sterilization specification and be done with it," says Foster. The initiative has also benefited internal operations. "I know from where I sit that they're doing the same thing in Charlotte[NC] and in Corona," she says. "I don't have to worry that they're writing their own procedures."

Foster and Hans Aeschlimann, her counterpart for IBA Europe and Asia, currently are wrestling with language issues before rolling out the harmonized QS at European facilities. Industry is extremely eager to see the system implemented overseas, according to Foster. "On the EtO side, in particular, Griffith purchased companies one at a time, and because of language barriers and so forth, these firms maintained their individual quality systems," she explains. IBA's European program will introduce a common policy manual and QS level procedures for the facilities, with some variations in the work instructions in the policy procedures section. Foster expects the harmonization of European facilities to be completed in 2002.

Taking Audits On-Line

IBA's North American operations are also readying a system that will allow device manufacturers to perform on-line audits.

"Device manufacturers are required to audit contract sterilizers," says Foster, "but many are not doing so. In our Corona facility, for example, we have close to 400 customers, yet we average about 58 customer audits a year." Travel expenses are one of the primary reasons that companies forego audits, she adds, "so we decided to make them available, down to process procedures, on the Internet." IBA in North America is considering adding other features to the controlled-access Web site, notably making batch records accessible on-line.

This service will benefit both smaller companies, which can't always absorb the cost or inconvenience of having key employees away from the office, and larger firms that have numerous vendors to audit. The latter "can do a desk audit in their office instead of coming here and reading procedures for a day," says Foster.

At the time of writing, the on-line audits were undergoing beta testing. Foster expects the service to go live by the end of June 2001.

Norbert Sparrow

Magnum Plastics to Produce Safety Syringe

Magnum Plastics to Produce Safety Syringe

Magnum Plastics Inc. helped produce this safety syringe that reduces the risk of contamination for health professionals.

A medical design company has selected Magnum Plastics System LLC (Erie, CO) to produce a one-handed safety syringe that lessens contamination risks for health professionals. Developed by DeHardCap Safety Syringe System LLC (New Orleans, LA; www.dehardcap.com), the syringe uses a spring-loaded plunger that is activated with a single finger. When the needle is removed from the patient, a plastic sheath with a stainless-steel hatch permanently caps it regardless of the remaining fluid level. A piggyback attachment, the product can be tooled for most existing syringes with minimal changes. According to DeHardCap vice president Lawrence Deharde, Magnum Plastics was selected for this project because of the firm's technical expertise and experience dealing with FDA. "Magnum," he explains, "had the necessary staff to work with us through the design and engineering phases all the way up to final production." Magnum Plastics, a contract molder, will manufacture and assemble the syringes at a new 20,000-sq-ft production facility. The FDA-registered company, which is certified to ISO 9001 and EN 46001, has 11 injection molding machines, an in-house tooling source, and a 2100-sq-ft cleanroom. Mass production of the syringe will begin in the fourth quarter of 2001.

Zachary Turke


Discovery May Lead to Longer-Lasting Artificial Hips

Discovery May Lead to Longer-Lasting Artificial Hips

Researchers at the Swiss Federal Institute of Technology (Zürich, Switzerland; www.kof.ethz.ch) have made a discovery that may significantly extend the usable life of the materials used in replacement hip joints. Performed on more than 300,000 people every year, hip replacement procedures frequently use a joint consisting of a titanium alloy base with a polyethylene cup that is fitted with a ceramic ball. Even these advanced materials, however, tend to degrade after 10 to 15 years, often because of inadequate lubrication. Although replacement hips use synovial fluid, which is present in natural joints, to reduce friction, they don't receive the same level of lubrication.

Swiss researchers have focused on the polyethylene cup as the source of the problem. Natural cartilage is hydrophilic; polyethylene, on the other hand, repels water. This condition causes the protein in synovial fluid to denature, turning inside out and losing most of its lubricious properties. The team tested this assertion by treating polyethylene with oxygen plasma to reduce its water-repelling properties. Once treated, the material did indeed experience greatly reduced friction. "We would expect replacement hip joints constructed with similarly hydrophilic materials to have a longer life expectancy than current models," summarizes researcher Nicholas Spencer. Spencer goes on to say that this discovery is particularly important as "bone structure deteriorates gradually over time, making repeat transplant procedures more and more difficult." Because the polyethylene currently used only retains this increased lubricity for a matter of minutes after treatment, the research team is now working on developing derivative materials that have these traits intrinsically.

Zachary Turke

Display Integrated into Surgical Microscope

Display Integrated into Surgical Microscope

Integrated into the MultiVision microscope, CMD's microdisplay allows surgeons to view either microscopic or endoscopic data.

Neurosurgeons rely on many sources of information to guide them through surgery, sources that include surgical microscopes, endoscopes, and computer-generated navigational data. To improve microsurgical procedures, Carl Zeiss (Oberkochen, Germany; www.zeiss.de/surgical) selected microdisplays from Colorado Microdisplay (CMD; Boulder, CO; www.comicro.com) for use in its OPMI Neuro MultiVision microscope. With the CMD microdisplay in the eyepiece of the MultiVision system, a surgeon is provided with all of the information needed without having to look away from the microscope at other monitors. Using either a handgrip or a foot pedal, the surgeon can easily switch between the images from the microscope and endoscope. Viewing the microscope image in conjunction with a microdisplay also allows navigational overlays and other data to be projected into the microscope image, further improving the surgeon's efficiency. "CMD's microdisplay system provides crisp, beautiful images with outstanding contrast, color, and brilliance, and was the optimal solution we needed to consolidate the different images and views in the microscope," said Dirk Brunner, business unit manager of neurosurgery, spine, and ENT at Carl Zeiss.

Carl Zeiss's OPMI Neuro MultiVision microscope simplifies and enhances endoscopic-assisted surgery.

"Multivision enables us to simplify the process, allowing more effective and more reliable endoscopic-assisted microsurgery."

Katherine Sweeny


Sapphire Engineering and Upchurch Scientific Merge

Sapphire Engineering and Upchurch Scientific Merge

Sapphire Engineering Inc. (SEI; www.sapphireengineering.com) of Pocasset, MA, a 100-year-old manufacturer of precision components made from hard materials, has joined with Upchurch Scientific (www.upchurch.com) of Oak Harbor, WA, under the banner of their newly designated parent company—Scivex.

SEI makes precision parts from such materials as synthetic sapphire, ruby, and zirconia ceramics. These materials are known for their inert characteristics and are therefore preferred in the analytical and HPLC instrument markets as wetted component parts in liquid-handling and -detection systems.

The company provides sapphire pistons and ruby ball-seat valves worldwide. It has also offered increasingly complex turnkey subassemblies to OEMs, ranging from complete pump heads and check valves to flow-cell assemblies. Other products include microball lenses and assemblies for fiber optics, technical sapphire components for industrial applications, and low-pressure positive-displacement and dispense pumps.

Upchurch Scientific is a manufacturer of precision fluid-transfer fittings, filters, valves, tubing, and accessories. The company specializes in close-tolerance injection molding, machining, and extrusion of high-end engineering thermoplastics. Key markets for Upchurch include analytical instrumentation, medical devices, and diagnostic products.

Karim Marouf

Coatings for Plastics Provide Flame Retardancy

Coatings for Plastics Provide Flame Retardancy

Flame-resistant coatings were used on the molded parts of an endoscope reprocesser.

Intumescent coatings from Flame Seal Products Inc. (Houston; www.flameseal.com) have recently received a UL 94V-0 rating. Minntech Corp. (Minneapolis; www.minntech.com), a medical equipment supplier, funded the tests of the flame-retardant coatings in anticipation of using them on its plastic products. The thin-film Flame Seal coatings, which provide flame resistance without compromising tensile strength, were used on the molded parts of an endoscope reprocessor.

Flame Seal president Michael Kiser says it is difficult for a plastic to obtain the UL 94V-0 rating. "It is unusual for polyethylene or any other plastic to have a coating with sufficient flame retardancy," he says.

The basis of the FX-100 and FX-PX coatings is an amine polymer system. The clear system, composed of a 4:1 ratio of polymer to curing agent, is cross-linked and applied to substrates in three layers, each air dried and measuring from 2.0 to 2.5 mil in thickness. When a fire occurs, the coated products change dramatically, going through various stages of expansion and performing distinct yet simultaneous functions. The coatings automatically react with fire or heat to convert combustible gases and tars into noncombustible carbon char, nitrogen, and carbon dioxide.

The chemical reaction creates an intumescing action as water vapor is released to cool the plastic substrate and as nitrogen and carbon dioxide are liberated. The escape of the gases causes the coating to expand up to 100 times its original thickness. The expansion results in a pure carbon char that provides an intumescent seal around the underlying plastic substrate.

Karim Marouf