Electronic Design

Lifesavers Come In Many Technological Flavors

Already playing a leading role, MEMS, nanotechnology, and robotics are rapidly marching toward more effective medical diagnostics, drug delivery, organ replacements, patient monitoring, and prosthetics.

There's no question that science is destined to improve and extend the human life experience. Microelectromechanical systems (MEMS), microfluidics, nanotechnology, lab-on-a-chip devices, DSPs, implantable genetic chips, and robotics are all combining to ensure our health. The result is the dawn of a new technology age, with electronics engineers, chemists and chemical engineers, biologists and bioengineers, medical doctors, ethicists, physicists, and mechanical engineers all working in concert.

One particularly hot area, bio-hybrid organs, combines living cells with polymers and silicon. These organs get their structure from inorganic materials while the living cells—grown from cadavers, animals, or human tissue—perform the complex tasks they do best, such as processing bio-chemicals and filtering blood. These devices alleviate medical conditions and extend lives. Ultimately, the goal is to implant them in the human body for maximum effectiveness. Complete organ implants will be the next step.

Researchers at the University of Missouri at Columbia recently demonstrated a process that one day may enable the formation of ink-jet-printed human organs. The printed organs are formed from the organ donee's cells to ensure biocompatibility with the donor, whose cells would be printed in layers alternating with structural gels.

One such bio-hybrid organ, the renal assist device (RAD), has been shown to improve the effectiveness of conventional kidney dialysis machines (Fig. 1). Researchers also have developed a liver bio-hybrid organ (Fig. 2). Scientists at Charles Stark Draper Laboratories are working on a microfluidic device that's 1 mm thick and 25 cm2 to ultimately produce a complete liver on a chip. Also, MIT researchers are working with J.P. Sercel Associates on cell-holding scaffolds made on laser-machined polymers (polycarbonate, polyethylene terephthalate, and polyimide). These scaffolds have extremely small channels and pores that may enable the researchers to one day produce a liver on a chip.

At the McGowan Institute for Regenerative Medicine at the University of Pittsburgh, a bio-hybrid lung is being developed to emulate the gas-exchange function of a normal lung. This MEMS device is laced with microchannels containing either air or blood. These microchannels are separated by thin membranes that mimic the behavior of the alveolar wall of a normal lung.

Of course, the ultimate organ—the heart—is not to be forgotten. For example, there are bio-hybrid organ "patches" that act as bandages, repairing damaged parts of failing human hearts. At the Massachusetts Institute of Technology, researchers plan to begin animal tests for cardiac tissue constructs they call "contractile patches," which replace damaged heart tissue. Research also continues on developing entirely implantable hearts.

THE EYES AND EARS HAVE IT
Two of the most successful human-organ technological achievements concern artificial eyes for the visually disabled or blind and artificial ears for the hard of hearing and deaf. In fact, bionic eyes and retinal and cochlea implants are already here.

One ambitious program involves the University of Southern California's Doheny Retina Institute and Keck School of Medicine, Second Sight LLC, Texas Instruments, and U.S. national laboratories. These groups are trying to produce an artificial retina, which already shows great promise. The work is being funded by the U.S. Department of Energy (DoE) under the auspices of the DoE's Artificial Retina Program. A 60-electrode retina was squeezed into a 5-mm2 area retinal platform (Fig. 3). It's believed to be the highest channel-electrode density per unit area.

Another ambitious retinal prosthesis project, funded in part by the U.S Air Force and VSX Corp., is working on a means of directly stimulating an eye's inner retina without using signals to restore some degree of sight to visually impaired individuals. The 3-mm chip lets users perceive 10° of vision.

Combating blindness is also a goal of the University of Utah, working with Oak Ridge National Labs and the University of Tennessee's Health Science Center. Similar work is ongoing at MIT as well as at universities in Japan and Germany.

Bionic ear development can be summed up in one word: spectacular. The University of Michigan has already created the first MEMS lifesized implantable mechanical cochlea. These implants work by sending signals for different frequencies to electrodes implanted in the cochleal spiral. The auditory nerves then transport these signals to the brain. Arrays of sensors added to the mechanical cochlea help drive the electrodes in a cochleal implant.

For the hard of hearing, NVE Corp. developed giant magnetoresistive (GMR) sensors that automatically adjust the sound's volume in hearing aids without the user's intervention. These spintronic GMR sensors, built by Starkey Laboratories, work by acting on an electron's spin rather than its charge to store information.

For the deaf, the Georgia Tech Research Institute licensed a wearable captioning technology to Peacock Communications, which is offering a software system it calls COMMplements. The software taps into IEEE 802.11b wireless transmission capabilities to give deaf mobile users easy Internet access to captions for sporting events via PDAs.

BETTER MONITORING, DIAGNOSTICS, AND WARNING
One way to minimize diseases is to come up with more accurate and effective non-invasive monitoring, diagnostics, and early warning aids. Swallowable imaging pills provide gastro-intestinologists a more accurate view of the small intestine than ever before through wireless RF imaging (Fig. 4).

At the University of Calgary, researchers produced a prototype of a MEMS-based electronic mosquito. Called "e-mosquito," it emulates a mosquito's blood extraction (Fig. 5). Its goal is to provide controlled sequential actuation and arraying of microneedles that penetrate the human skin to sample a very small amount of blood for further analysis. The device offers a comprehensive and practical solution for wireless-controlled and painless, real-time, semi-invasive blood analysis and physiological cell interrogation.

New DSP ICs are being brought to bear for better non-invasive diagnostics. Take the Piesometer MK-1 portable blood-pressure monitor from Canada's Canamet Inc., for instance. It uses Atmel's Diopsis dual floating-point very-long-instruction-word (VLIW) DSP as well as an ARM microprocessor that overcomes the limitations of the conventional auscultatory method. The latter method employs a mercury sphygmomanometer, as well as the oscillometric technique used by automatic blood pressure machines. Canamet's device permits adaptive signal-processing methods that include adaptive interference cancellation, bandpass filtering, and peak-discrimination algorithms.

Implantable lab-on-a-chip devices, sometimes called bio chips, ultimately will hold the key to non-invasive monitoring, diagnostics, and control. Many of these devices are designed using MEMS technology. One of the first companies to introduce such bio chips was Affymetrix, which introduced the GeneChip back in 1994. Agilent Technologies, Biosite, Cepheid, CombiMatrix, Nanogen, and STMicroelectronics have since followed with sophisticated platforms. These bio chips constitute a huge molecular electronics market that should explode within the next few years.

The growth of bio chips gives rise to a new term—bioinformatics—the technology needed to process the massive data output from lab-on-a-chip devices and DNA chips. This requires the marshalling of computers, databases, and algorithms. It's exemplified by the huge amounts of data needed to process and analyze just a single lab-on-a-chip, such as Affymetrix's GeneChip (Fig. 6). Having to extract meaningful information from this gargantuan mass of data is challenging the electronics industry in ways that echo what businesses faced during the development of information technology.

Beyond the implantable realm, scientists at Sandia National Laboratories are hot on the trail of a portable 5-lb handheld medical diagnostic device that can instantly detect heart and gum diseases (Fig. 7).

HELP FOR THE DISABLED, TOO
There's no shortage of advances in prosthetic and orthotic devices to improve the quality of life for the disabled. These include robotic arms that could help stroke survivors regain their range of motion; assistant robotic machines for the crippled; and brain implants that allow paralyzed individuals to operate a prosthetic arm using only their brain and the implanted device.

Where will all of this lead? Microfabrication, nanotechnology, robotics, and bio-engineering will come together to diagnose cancer tumors more quickly and accurately. On top of that, they'll be able to destroy those tumors well before they cause bigger problems. That's the goal of a group of researchers at the University of Washington. With their research, patients will be able to inject self-assembling nanoparticles that would find early stages of cancers and perhaps coat and destroy small tumors with drugs.

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