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Miniaturization, Electronics Powering Breakthrough Medical Designs

Medical electronics

Functionality is on the rise as enabling technology creates possibilities for medical parts that weren't manufacturable until now.

Two industries that are expecting high growth over the next five years--medical devices and consumer electronics--have a lot in common these days. In both industries, the need for miniaturization is driving the development of devices that pack enormous complexity, sophistication, and functionality into ever-smaller components. Medical devices have become one of the prime application areas for electronic components, and as these components become more and more critical to the performance of medical devices, the two industries are becoming increasingly intertwined.

Today, for example, the medical industry is making greater use of electronic components and technologies, such as RFID and Bluetooth, that are flourishing in the consumer products space, according to Scott Nelson, executive vice president and chief technology officer for LOGIC, a Minneapolis-based product development and manufacturing company that provides product design, engineering, and electronic manufacturing services.

"Medical devices are looking, and often behaving, more and more like consumer products," says Nelson. "They have more interaction design, more RF integration, and shorter life cycles."

Nelson attributes much of today's "above-average" market growth for medical applications and devices to worldwide demographic trends. Predictions that baby boomers will be spending more money in an effort to remain healthy seem to be on target, he says, noting that the trend toward preventive care is not only growing, but linking new and innovative technologies with health care. Medical devices are becoming more and more interconnected with patient information systems, leading to an increasingly greater role for information management and IT system integration in medical device applications. This trend has also heightened the need for processors that provide the resources required by medical products for simultaneous user applications, communications, and device control.

In response to consumers' need for smaller, easier-to-use medical products, LOGIC recently teamed with Texas Instruments (TI) to release a new development kit designed to bring new medical products to market quickly. The new ZoomTM Medical OMAP35x Development Kit and companion System on Modules (SOMs) use TI's OMAP35x processor, and are intended to provide product developers with a cost-effective, compact way to design and produce medical, industrial, and other embedded applications. Medical product companies can use the development kit to easily develop sophisticated integrated medical devices with advanced graphical user interface (GUI), smart and real-time physiological processing, and wired and wireless connectivity options for patient monitoring and data logging applications.

As demand for medical devices continues to spiral upwards in the U.S. and abroad, new products are being developed at rates that put pressure on companies to get their products to market faster. The U.S. Food and Drug Administration (FDA) has responded by tightening its oversight on the product design and development process, intending to catch defects early enough to eliminate the need for recalls. Manufacturing processes, too, are subject to increasingly stringent standards.

"Greater regulatory scrutiny suggests that there will be less tolerance going forward for medical devices to be defective," says Microfabrica Executive Vice President, Technology, and Chief Technology Officer, Adam Cohen. "Which means you'd like to reduce the intrinsic [manufacturing] process variability."

Maintaining Part Functionality at the Smallest Scales: A Tall Order for Tiny Parts

As medical and surgical procedures have become less invasive, the need has increased for ever-smaller devices that maintain or increase the functionality provided by devices used in the traditionally more invasive procedures. It's an extremely tall order, however, when you consider that the production of tiny parts by conventional manufacturing methods has often proven to be difficult and, in many cases, impossible. But it has opened the door for new enabling technologies that can reliably and cost-effectively produce small, complex metal parts for the devices used in minimally invasive procedures.

Microfabrica, Inc., a company that designs, develops, and manufactures custom, micro- and millimeter-scale mechanical components and devices, has targeted this market need. The Van Nuys, California-based company has developed a unique technology, known as EFAB®, through which it provides flexible and accurate manufacturing of highly-miniaturized metal (e.g., nickel-cobalt) components and mechanisms in production volumes. According to Cohen, the technology reduces the intrinsic variability of a manufacturing process because it doesn't make parts or devices one at a time, but in batches.

"The geometry of the devices in that batch is defined by a very precise process of photolithography, which is the process that's used to make semiconductor chips," he says. "It tends to be a very repeatable process as long as you keep it clean, and indeed, we make our devices in a cleanroom. You're using a very precise piece of tooling--a photomask--to define where material is and where it isn't. That's how we're making our metal devices. We're really the first people to come along and say, 'Let's use the precision wafer-scale fabrication methods that are found in the semiconductor industry to make three-dimensional mechanical parts and mechanisms.' That intrinsically instills our approach with a built-in repeatability that you just don't get with other approaches."

The result, Cohen says, is a process that's nearly invariable. "When you think about how normal devices are made, there are a lot of different process steps and they're executed in slightly different ways, depending on what the geometry is. When you actually build up something in layers, all you really have to do is learn how to make a layer really well, and then you can make any layer you want, and it's the same thing all the time. So we have a very versatile process that only requires that you master the steps of making a layer, and then you can build a lot of things. We can get very good at building those layers, and building them consistently, no matter what the geometry is."

For this reason, Cohen says, EFAB is preferable to trying to accommodate a wide variety of geometries when using conventional machining processes to produce tiny parts. Conventional machining methods require the user to "always do things a little bit differently, to optimize certain tolerances," and to grapple with issues like tool wear.

Microfabrica manufactures micro- and millimeter-scale mechanical parts and devices for a variety of medical, electronics, and defense applications. Its capabilities are said to range from "feature-rich, static millimeter- to centimeter-scale devices with micron-scale features, to fully assembled micro-mechanisms with dozens of independently moving parts, all without any assembly." While its main business is the custom manufacturing of small, precision metal parts and devices, Microfabrica also provides design and development services.

"There are three fundamental ways that people can access the technology from us," says Cohen. "One is that they will occasionally come to us with a full-blown design, perhaps with some manufacturability modifications on our part. At the other extreme, they may come to us with a sketch on a napkin, a concept, a list of specifications, and they rely on us to do the design of a device. And in between is sort of a collaborative model, in which they may have more than a sketch on a napkin, but there's a back-and-forth exchange in which we jointly develop the design."

Earlier this year, the company introduced a set of highly-miniaturized "building blocks," which designers of minimally-invasive medical devices can use to develop innovative, highly functional products that are difficult or impossible to produce using conventional manufacturing processes. These EFAB building blocks include micro-turbines, micro-chainmail baskets, and two- and four-direction expanders that resemble miniature car jacks. They are applicable to a variety of medical products, such as atherectomy and thrombectomy devices, drug delivery devices, distal protection devices, and miniaturized surgical instruments. But they can also be used to develop tissue approximation devices, advanced guidewires, and coil delivery devices, the company says.

"If you think about the need for minimally invasive procedures, by definition that means that you want to go through a small incision to do something significant--something that you normally would have to be quite invasive to do," says Cohen. "That means you have to have high functionality in a small space. And as you miniaturize something, in the interest of obtaining the same result that you had before you miniaturized it, you have to retain or sometimes increase the complexity of the device. That's an issue that's difficult to deal with on a small scale for a lot of technology."

All of this has to be achieved in an instrument that's still affordable, Cohen says, and it has to be done in a way that's consistent and repeatable from device to device. "That translates into growth opportunities for us in that we have the ability to make very consistent parts, because of the way we do it, and the ability to reduce costs not only by increasing the yield (which means you have greater consistency), but also by reducing the costs of assembly and reducing the costs of the labor."

Cohen says that Microfabrica has developed a technology that's unique on any scale in that it builds up fully functional multi-component devices without the need for assembly. He distinguishes the technology from rapid prototyping, which doesn't generally produce functional devices so much as models or patterns.

"When you build something up in layers in our process, you have the ability to incorporate multiple components such that a part of each is in each layer," he explains. "And as long as they're separated from each other during the assembly process by something that creates a gap, if you will, once you remove that separating material (the sacrificial material), the individual parts can articulate and form a completed mechanism that can actually function.

"The simplest example is probably a chain in which you have links, which would normally have to be made separately, and then interlinked with each other, and perhaps welded.  We would build the entire chain in layers, with a part of each link on each layer, separated by sacrificial material, which embeds everything as the process moves along."

There are some limits to the technology that the company is working on, according to Cohen. For example, he says that it's currently possible to achieve smaller clearances between one moving part and another using an assembly technique. But he's confident that EFAB can give designers greater flexibility.

"When you think about what they have to do now, it's essentially taking standard shapes and standard processes, and trying to adopt them to their needs," he says. "With medical devices, you'll often see people taking tubing and wires, and they'll cut the tubing--they might laser machine it. They might bend the wire or machine it; they might weld tubing and wire together to make a more complicated shape.

"But what they don't really have at the small scale is a true freeform process, where almost anything that designers want, they can build. They really start out with, 'Okay, I need to achieve this functionality, and I know I have available to me wires and tubes and flat strips. How can I cobble together a solution that is manufacturable from those standardized shapes and standardized processes that are available to me, such as machining and grinding and welding? Now, of course, you can use CNC machining to make some parts, but there's a limit to what you can do there because of the delicacy of these structures.

"We actually do think that when you give people the ability to grow a structure according to the CAD design that you've come up with, it really does increase flexibility, it frees up the imagination. A lot of people say to us, when looking at our process, 'We've got to whip out our old notebooks and look again at the ideas that we shelved years ago, simply because we could never figure out how to manufacture them.' "

Designers of minimally invasive medical devices, he says, will find EFAB useful because it gives them the ability to do things that they couldn't do before. "We're viewing this as an enabling technology for new devices and new ideas," says Cohen. "It gives them the ability to reduce costs in things that maybe they can do, but not particularly economically, and to improve quality and consistency. I think those are the main design benefits at this point.

"Really, imagination on the part of medical device designers, or any designers, is limited by what can be made, and there's a lot that really could not be made before this at the millimeter or smaller scale," he says. "We think we can make quite a bit of it."

Microfabrica is currently producing parts in prototype and evaluation quantities for medical OEMs. The company is already in volume production for clients in the semiconductor industry, and expects that to be the case for its medical industry clients by sometime next year. Earlier this fall, Microfabrica closed a $22.5 million Series B financing round, co-led by the venture capital firms Versant Ventures and Interwest Partners, both top-tier investors in the medical device market space. Although some of the investment will be used for continued expansion of production capacity and capabilities in Microfabrica's growing electronics and defense businesses, the funding is primarily targeted at expanding the company's products and capabilities in minimally invasive medical devices.

"Microfabrica is a visionary company, pursuing a fundamental new wave in medical device development--micro devices--the next generation of minimally invasive medical devices," said Kevin Wasserstein, managing director at Versant Ventures, in a statement announcing the financing. "Microfabrica's remarkable technology enables extraordinarily sophisticated and unique metal micro-scale/MEMS-scale devices and micro-machines which were previously impossible or impractical to design and manufacture."

Custom Electronic Product Design and Development

The medical industry is known for its emphasis on standards and regulations that must be followed, depending on the type of device being designed. Designers must demonstrate, through adequate testing and documentation, that product requirements are being met. The FDA and similar bodies in other countries have various rules, regulations, and guidance. Many of these requirements are fulfilled by adhering to appropriate third-party standards--published by organizations such as IEC, ISO, AAMI, and UL--for a given device.

"With regard to medical electronics, there's certainly been a trend toward more regulation and increasing scrutiny about the design process as a whole," said Paul Nickelsberg, president and senior engineer at Orchid Technologies Engineering and Consulting, Inc., a Maynard, Massachusetts company that specializes in the design, product development, and production of high-tech custom electronics.  "That represents opportunities and difficulties for organizations that are trying to sell or bring to market medical devices."

Nickelsberg can attest to the huge panorama of applications that have opened up for medical electronic devices that do things like measure temperature and pressure, or turn a pump, or radiate something with energy. "It's such a wide field," he says. "We've worked on everything from CT scanners to infrared light detection equipment. Some of them are very tiny and simple, and some of them are absolutely enormous and full of all kinds of regulation."

One of Orchid's medical projects was the design of a high-speed transconductance amplifier, a device that detects buildup of plaque in veins and arteries by sensing the tiniest variations in fluorescent light levels inside the human body. The amplifier system is excited by a laser light source and is reported to be capable of detecting infrared light levels below -40dbm, with a frequency response flat to 35 KHz. Orchid provided multiple iterations of the system design, helping its client through the proof-of-concept phases of a technically challenging project.

"A transconductance amplifier is useful because it is capable of reading very low levels of light or turning low levels of light to a usable electronic signal," explains Nickelsberg.  "And you can imagine that there are all kinds of applications where low levels of light are used for things like, in this case, sensing the reflectance of plaque. It's an amplifier that would be used to detect those very low levels of light--like nanowatts or pico watts--almost to the point of single photons. There are all kinds of applications for it, including CT scanners, which work with very low levels of X-ray light."

Positioned on the end of a rotating detector mechanism, the front-end amplifier uses slip rings to carry power and encoded data signals to stationary computer equipment. It also makes use of custom encoded, serial data-communications protocols to pass data and control signals between stationary and rotating equipment. A major part of Orchid's custom design work involved selecting the appropriate slip ring and data communications technology. The company also employed analog circuit modeling techniques, advanced on-the-bench prototyping and testing techniques, and signal-source fixturing to design what it called "a reliable, accurate, and highly-repeatable transconductance amplifier." In addition, Orchid designed digital electronics that made it possible to digitize the data that came from the amplifier. "All of this was used in a very early research tool that proved the science," said Nickelsberg.

Using specialized software to carefully simulate how a component, such as the amplifier, would work plays an important role in engineering. But there are times, according to Nickelsberg, when simulation doesn't quite tell the whole story because of an application's unique operating environment. In those situations, he says, there's nothing like actually building a rough prototype and trying it out. "Often, in an amplifier that's as sensitive as this particular one, things like noise, shielding, and power supply quality affect the operation of the amplifier so much that it goes beyond what we can do with just a plain simulation," he explains. "So it's nice to see the [prototype] working and actually tweak it right there on the spot."

Orchid serves several high-growth markets in addition to the medical industry, including avionics, power, consumer computing, and industrial applications. One of its specialties is redesigning obsolete equipment. The company has also established a foothold in greentech, designing electrical components for renewable energy technologies. "We've done motor controllers in the space of wind energy, and that's been very interesting," says Nickelsberg. "We've also been doing some work [involving] converters and things for the photovoltaic (PV) solar industry, because there are a lot of possibilities there."

Micro-Induction Coils Offer RF Signal Transmission, Power Induction Capabilities for Implanted Medical Devices

A new family of micro-induction coils for implanted medical applications and traditional biomedical devices is said to eliminate the potentially harmful effects on the human body caused by battery-operated medical implantable devices. The micro-induction coils, equipped with radio frequency (RF) signal transmission and signal and power induction capabilities, were introduced in June by Dynamics Research Corporation's Metrigraphics Division, a precision manufacturer of customized micro-components and micro-circuits based in Wilmington, Massachusetts.

Metrigraphics has reportedly prototyped more than 160 coil variations, allowing the company to offer clients flexibility in process technology, substrate material, size, and induction and tolerance ranges, as well as functionality. This flexibility, the company says, is necessary to meet "the most rigorous technical specifications" that haven't been fully addressed by other manufacturers. The new micro-induction coils are applicable for a variety of medical applications, such as miniature loop antennas for both active and passive implanted devices, biomedical micro-electromechanical systems (BioMEMS) sensor units, and neuro-stimulation devices.

The family of coils is classified by two groups--single- and multiple-layer forms. Single-layer, multiple-turn electroformed coils are available in various sizes and in round and square configurations, for ease of fit into specific applications. Multi-layer coils offer greater field density for more high-end applications. The coils are reported to provide a number of advantages--including a production process that yields high volumes of coils per sheet produced--over traditional offerings. For one, the materials don't react with body fluids, thereby reducing any potentially harmful effects. And because the induction coils permit passive devices, as power is obtained through induction only when required, they don't need internal batteries. They also eliminate the need for control and power wires to be passed through the body.

The process starts with a photolithographic image of the desired shape in photo resist. Either electroplating, for a thicker coil material, or sputtering, for extremely fine coils, can be used. Individual traces can be fabricated as small as three microns, but more typically in the five- to ten-micron range, with metal thicknesses equal to the trace width. Aspect ratios of 2.5 to 1 are also being fabricated and higher ratios are possible, the company says. Current samples have been fabricated on glass for ease of handling, but other substrates--including silicon, alumina, and cast polyimide--are possible.

"We are committed to delivering quality, reliability, and innovation with every product we make, whether it's for the medical device, telecommunications, semiconductor, or biotech industry," said Randy Sablich, vice president and general manager of DRC's Metrigraphics Division, in a statement announcing the new coils. "DRC's Metrigraphics Division recognizes the difference that our precision micro-components make for our customers, and we are honored to be working with many of the innovators making medical breakthroughs."

 Metrigraphics' micro-induction coils are available in sample form, and can be custom fabricated to each client's unique requirements. They are available in a variety of substrates, and are produced using electroformed nickel cobalt, over-plated with pure gold, or with hard gold, depending on the application. Coils can also be produced using copper.

"We've been getting a lot of inquiries for induction coils," Sablich told Design-2-Part Magazine in June while fielding questions at the MD&M East Conference & Exposition in New York City. "So we built a bunch of coils, and we've had some of them characterized. We show them to people with the expectation that in large measure, people are going to come back to us and say, 'Okay, I want a coil just like that, but can you make it a little thicker, can you put more turns on it? One guy just came by and said, 'Can you drill a hole through a backplane on the backside and through-plate it?' It's really to get the dialogue going. But it's also to branch out a little bit. In the case of the coils, particularly in the medical device business, we're addressing the need for the ability to transmit signals and power from outside of the body to inside of the body."

Sablich says that Metrigraphics' technology provides an alternative to the conventional use of control circuits for medical devices. Rather than using a control circuit that's inside the body and always drawing power, it's now possible to use a passive control signal. "You activate it with an RF signal and power," he says. "Turn the signal on, tell it what to do, it turns off, and the device continues to go."

Metrigraphics doesn't design the devices, but the company can make biocompatible coils of various sizes and shapes using inert materials, such as gold or polyimides, that have been qualified for use inside the human body. The process starts with photolithography--the same process used in the semiconductor industry. "They do things to a finer degree, and we go down to feature sizes as low as 3 microns," says Sablich. "Typically, 5-10 microns is the sweet spot for our processes. Then, unlike the photofabs who will use chemical material removal processes, we'll use additive processes. So we'll plate up copper, gold, nickel, nickel-cobalt, or we'll sputter them, and then we'll do multiple layers--again putting down photoresist, imaging it, plating it up or sputtering it up, and removing the photoresist material."

Although most of the company's work has been geared toward producing a component, Metrigraphics says that some clients may just want one or some of the processes needed to produce the component. "For example, in some of the nanotechnology-related businesses, people are coming to us and asking if we'll just create an image, put a thin film on it, and then give it back to them. Then they'll take it from there; they'll do the rest of the processing. Some people come to us and say, 'I've got a silicon wafer, can you put 5000 Angstroms of gold on it?' Sure. We'll do that for you."

The medical device industry is the fastest-growing segment of Metrigraphics' business, but it's not the only industry that it serves, as the company also counts telecommunications, semiconductor, and biotech companies among its clients. Much of the company's work is applicable to optics, and some of the parts that it makes are electronics. Companies in the test and instrumentation industry also look for miniature coils and miniature circuits, according to Sablich.

"We started out 46 years ago, making optical encoder discs--linear and rotary encoder discs for precision encoders. While we still do that today, we moved to making nozzles for inkjet printers.  We've delivered well over a billion nozzles to Lexmark for inkjet printers. Then we began using our technologies and skills to make some of the medical device parts. And that business is really beginning to take off. 

"The only overarching connectivity between the different markets that we serve is the need for miniaturization," he continues. "They're all looking to do this communications task in smaller and smaller packages, lighter weight."

An example of that communications task is in the biomedical industry, where some companies are looking at various kinds of optical devices to aid people who've lost their sight. These types of applications highlight the need to communicate with devices that are inside the head. "You don't want wires hanging out the side of your head, so you want some way to induce the signal to control that device," says Sablich. Other applications, he said, involve using the micro coils as pure inductors. They can be mounted inside the body to protect other devices, already in the body, from high-strength X-rays and other diagnostic procedures.


New Functionality for Medical Devices 

Forceps Actuated by Fluid Pressure

Making fluid pressure work to advantage in situations where friction can interfere with a physician's attempts to operate a device was the idea behind Microfabrica's development of its hydraulic forceps building block. The device makes use of a curved piston inside a curved cylinder, with a fluid conduit through the handle. It has a fixed jaw and a moving jaw that's rotated by the force of fluid.

"The idea is to actuate a device that can grasp, like forceps, not using a mechanical method, such as a wire or a rod, but using fluid pressure," says Microfabrica Executive Vice President and Chief Technology Officer, Adam Cohen. "And why would you want to do that? Well, the main reason is that if you're trying to do something through some tortuous anatomy, like a blood vessel that's very hard to get through because it's so winding and narrow, you can apply some fluid pressure to the device and cause it to actuate in essentially a frictionless manner. Because a wire that's sliding is subject to friction, particularly if there are a lot of bends and twists in the tube through which it would be guided."
 

Miniaturized "Car Jacks" Expand in Two or Four Directions

Millimeter-scale expanders that resemble tiny carjacks offer another element of functionality for the design of medical devices. Microfabrica envisions that their ability to expand outwards will enable the design of products that can be used to anchor a device, such as a catheter, for stabilization inside the anatomy. They can also be used to exert force in order to expand a particular part of the anatomy. Microfabrica has developed these miniature building blocks to expand outwards in either two or four directions. Both types of expander use tiny "shoes," or struts, which are pivoted and expand outwards to a large diameter when a shaft is pulled.

"The two-and four-direction expanders are slightly different in design, but basically they have 'shoes,' if you want to call them that--some surfaces that can press against tissue--which are pushed outward by some linkages," says Cohen. "In the case of the two-direction, that particular one has shoes coming out within a single plane, in two directions. In the case of the four-direction, these shoes are coming out of all four surfaces of the device that has a rectangular cross section. It expands not just in the plane, but omni-directionally.

"And again, these expanders are building blocks. They don't by themselves constitute everything you need for a procedure; they're one element of a potential medical product that would need that kind of functionality. Let's say you want to anchor in some position so that you have a stable platform on which to perform some procedure. You can get that functionality off that kind of building block. Most of them are actuated by pulling or pushing on a shaft of metal."


For more on LOGIC, see Minneapolis Firm Playing Key Role in Electronic Product Design, Engineering, and Manufacturing for Medical Industry; or visit www.logicpd.com.

For more on Microfabrica, visit www.microfabrica.com.

For more on Orchid Technologies Engineering & Consulting, Inc., see Massachusetts Firm Develops Robust Architectures for Electronic Products, or visit www.orchid-tech.com.

For more on Metrigraphics, visit www.drc.com/metrigraphics

This technical information has been contributed by
Dynamics Research Corporation's Metrigraphics Division

Click here to find suppliers

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