Electronic Design

The Pulse Quickens For Cutting-Edge Medical Electronics Advances

Picture this: A heart patient is experiencing fluid buildup in the lungs—an early sign of heart failure. But, an implantable sensory medical device in the patient emits a signal to both the patient and his physician via a Bluetooth-equipped mobile phone, warning them of impending danger. Wishful thinking? Not really. The technology is already here and is continuously being refined. All that’s missing is the supporting infrastructure.

Mir Imran, an inventor and entrepreneur at InCube Inc., presented this scenario as part of a panel on medical electronics at last month’s 2009 International Consumer Electronics Show (CES) in Las Vegas. The panelists discussed the vast potential of implantable devices that can accurately and quickly monitor and treat patients anywhere for chronic ailments such as heart disease, epilepsy, diabetes, and Parkinson’s disease.

And there’s much more to improving healthcare than sensory implants. Devices like insulin pumps are now available to service entire organs. Implantable vision systems are making notable progress. Microelectromechanical-system (MEMS) and carbon-nanotube (CNT) neural implants are providing a vast range of information about how human beings behave.

The tools needed to diagnose and treat many health conditions are improving daily. Some surgical instruments can access nearly every part of the human body via catheters. Slow-release drug capsules are becoming more effective and enhancing diagnostics and treatments. Externally wearable devices are vital to applications such as therapeutics. And, lab-on-a-chip devices can quickly sample, diagnose, and report on a patient’s vital medical signs.

Healthcare technology is poised to fulfill an urgent need. Roughly 80% of global healthcare costs are used to treat chronically ill aging patients. Some 600 million patients suffer from chronic diseases like diabetes, chronic obstructive pulmonary disease (COPD), congestive heart failure, and epileptic disorders. Longer lifetimes, a shortage of healthcare professionals, and spiraling healthcare costs all exacerbate the situation.

“Healthcare is a $2.5 trillion market in the United States alone,” says Andrew Rocklin, an analyst at Diamond Management & Technology Consultants. “Anybody who chooses not to participate could be giving up a potentially large amount of revenue.” But hurdles must be overcome before technology can have a real impact. Chief among them is a healthcare system, here in the U.S. as well as worldwide, that needs reform (see “Making The Healthcare System Technologically Friendlier” at www.electronicdesign.com, ED Online 20624).

HELP FOR DIABETICS AND HEART PATIENTS
Debiotech Inc. and STMicroelectronics announced the first prototypes of a disposable insulin pump patch (Fig. 1). Using microfluidic MEMS technology, the Nanopump passed initial testing stages and has been ready for volume manufacturing since last summer. Just one-fourth the size of existing insulinpump devices, it can be worn as a nearly invisible patch on the skin.

The Nanopump uses continuous subcutaneous insulin infusion (CSII), closely mimicking the natural secretion of insulin from the pancreas , whi l e detecting potential pump malfunctions for patient safety. According to the companies, it costs less and is a more attractive alternative than individual insulin injections that must be administered several times a day.

University of Michigan researcher Mark Meyerhoff is working for the U.S. Army Research Laboratory on subcutaneous implantable glucose sensors that monitor diabetes patients in real time. He’s using polymeric materials that catalyze the generation of nitric oxide (NO) at low concentration levels. Applied as coatings on surgically implanted amperometric glucose sensors, these materials would be more biocompatible than previous efforts since they reduce inflammations caused by implanted sensors. Cardiovascular disease is a common cause of death and disability. Heart diseases including arrhythmias result in about a third of all deaths in the U.S., spurring the development of a variety of medical monitoring devices and tools. One such device is a wireless electrocardiogram (ECG) patch monitor designed by Belgium’s IMEC (Fig. 2).

The monitor integrates electrodes, a biochip sensor, a microcontroller unit, and a radio in a package the size of a very thin wristwatch. Algorithms running on the patch’s processor monitor patients for arrhythmias day and night. The patch can run on a small 20- by 20- by 5-mm battery for about a week, with average power consumption of 2 mW.

A notable advance in therapeutic tools for cardiac rhythm disorders can be seen in a force-sensing ablation catheter from Endosense that treats cardiac disorders. The Switzerland-based company developed the first force-sensing force-ablation catheter, which gives physicians real-time objective measurement of the contact during a catheter-ablation procedure.

Physicians have treated this condition with conventional surgery to create lesions in the heart’s walls to eliminate abnormal cardiac electrical activity. But it’s difficult for physicians to assess whether or not they have created optimal lesions because there hasn’t been an accurate way to measure the force of the probe used to create them.

The TactiCath catheter is threaded up through a vein in the patient’s groin to the upper chambers of the heart. Through RF waves, it targets regions along the heart’s wall. Fluoroscopy, 3D mapping, and ultrasound provide outside guidance. Force, amplitude, and direction data are transmitted to a monitor from the catherer’s tip, giving physicians complete control over the ablation procedure (Fig. 3).

Germany’s Fraunhofer Institute for Microelectronic Circuits and Systems came up with an implantable blood-pressure sensing system, which is a goal for many researchers. Unlike cardiac pacemakers, the system doesn’t require an internal battery, since it’s powered inductively from outside the body. It consists of a sensor element and a transponder.

The sensor is inserted into an artery and connected to the transponder via microwires that are 10 to 15 cm long. The transponder, implanted under the patient’s skin, digitizes, pre-processes, and transmits blood pressure data. It’s powered through a tiny inductor that’s magnetically coupled with another inductor outside the patient’s body. This second inductor is part of a reading device carried by the patient.

The two inductors transmit electrical power to the transponder. At the same time, the inductors are used for wireless data exchange between the transponder and a reading device. Thus far, the researchers have been able to supply the implant with about 200 to 300 µW.

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Surgical implants of all kinds, like hip and knee replacements, may benefit from revolutionary intelligent materials that offer durability and safety. For example, researchers at the U.K.’s Science and Technology Facilities Council (STFC) in collaboration with Electrospinning Co. Ltd. and Anglia Ruskin University developed advanced nano materials that coat surgical implants. This encourages implants to bond with living bone and enables them to last the lifetime of the patient (Fig. 4).

“Ten percent of patients receiving surgical implants go on to develop infection and loosening of their implants, costing the United Kingdom at least £14 million every year and £224 million globally,” says Mansel Williams, chief executive of Electrospinning Co. “We want to eliminate this by creating the ideal implant surface matched to the individual patient, benefiting both the patient and the economy.”

LAB-ON-A-CHIP DEVICES COMING
The early diagnosis of heart attacks also benefits from lab-on-a-chip technology. A nano-biochip developed by the University of Texas at Austin uses a few drops of saliva to perform assays of heart conditions. The size of a credit card, the system can produce results in as little as 15 minutes. To minimize its production cost, the researchers use silicon nano-biochips microfabricated from sheets of stainless steel, making them 1000 times less expensive to produce than all-silicon structures.

At Purdue University, researchers employ an electrokinetic patterning technique that uses a laser and holograms to quickly position numerous tiny particles when analyzing biological samples for improved lab-on-a-chip performance. The researchers say the method allows for high-throughput chips using the smallest possible sample.

STMicroelectronics has teamed up with Veredus Laboratories Pte Ltd. to introduce the first lab-on-a-chip device for rapid molecular flu detection at the point of care. The size of a fingernail, the device employs STMicroelectronics’ In-Check MEMS microfluidics platform. It can identify and differentiate human strains of influenza A and B viruses, including the Avian Flu strains H5N1, in a single test. The researchers say it’s less complex, faster, and less costly than alternative detection methods.

The European Union (EU) has been funding the ambitious Smart BioMEMS project for complete DNA analysis using a portable diagnostic lab-on-a-chip device at the point of care. A prototype specifically designed for cancer testing and diagnosis is expected to be fully tested and demonstrated by the end of next month.

NEURAL IMPLANTS
The use of neural implants for studying, analyzing, and treating various parts of the body has been evolving rapidly over the last few years. For instance, the Eon Mini from the Advanced Neural Simulation (ANS) Division of St. Jude’s Medical Center targets spinal-pain management.

The researchers say it’s the smallest neurosimulator on the market for patients suffering from disabling chronic pain and other nervous-system disorders. Texas Instruments worked with ANS to produce the device, which utilizes TI’s microcontrollers.

Depending on the power output used to block the pain, patients can wear it from a week to a few months before its battery is recharged wirelessly. The battery is expected to last 10 years. The device delivers stimulation through 16 electrodes, which a physician can adjust individually to produce pulses of different intensities and frequencies. The patient can control the stimuli with an inductively coupled programming wand.

Epilepsy patients can look forward to promising work being performed at Purdue University. Researchers developed a miniature device with a transmitter that’s three times the width of a human hair and implanted below the scalp.

The device records abnormal neural signals relayed by electrodes in various parts of the brain, allowing it to “predict” when a seizure is about to start and then take steps toward prevention. The transmitter consumes 8.8 mW, which is about onethird that of other implantable transmitters, while transmitting 10 times more data.

Purdue researchers are also working on an inter-ocular sensor project to gain better insight into glaucoma, which can be prevented with enough advance warning. The disease causes blindness from a buildup of fluid pressure in the eye’s interior chamber, killing fibers in the optic nerve.

This condition is intermittent and requires continuous eye-pressure monitoring, allowing the patient to receive quick and effective treatment. The researchers placed the nanotech pressure sensor between two layers of tissue in the eye. It continuously measures the inter-ocular pressure and transmits this information to an external receiver.

There are many other efforts involving retinal implants. The University of California at Santa Cruz developed an artifical retina chip that’s been fabricated by Second Sight Medical Products. This nextgeneration Argus II Retinal Prosthesis System also is being funded by the U.S. Department of Energy.

The chip is implanted directly inside the eye on top of the retina. (It only works for patients whose retina has degenerated, but still have intact nerves connecting to the brain.) An array of electrodes stimulates optic nerve cells, sending an image to the brain’s vision centers. The plasticity of the brain’s vision-processing capabilities enables it to adapt to the artificially generated signals.

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SMART DRUG DELIVERY
Swallowable pills that deliver drugs in a controlled and targeted manner are the wave of the future for more effective and simpler treatment of a wide range of illnesses. Swallowable capsules containing imaging chips are also enabling more accurate diagnostics of internal maladies.

Developed by Philips, the prototype iPill includes a microprocessor, a battery, a wireless radio, a pump, and a drug reservoir that releases medication in a specific area of the body (Fig. 5). It also can measure temperature and report that data wirelessly to an external receiver. Philips says that delivering drugs to treat digestive tract disorders such as Crohn’s disease directly to the location of the illness means doses can be smaller, reducing side effects.

Controlled drug release allows maximum drug efficacy and minimal patient side effects. Implantation is one avenue for such control. MicroChips Inc. crafted implantable proprietary MEMS reservoir arrays that are embedded on silicon wafers and filled with biosensors or drugs for timed-release delivery. It allows for intelligent drug delivery in which small devices filled with potent therapeutic drugs are used in the body as needed.

Researchers at the Massachusetts Institute of Technology developed a drugdelivery system using gold nanoparticles that allows multiple (up to three or four) drugs to be released in a controlled fashion. The system is controlled externally. It takes advantage of the fact that when gold particles are exposed to infrared light, they melt and release drug payloads attached to their surfaces.

Two different shapes of nanoparticles were used—nanobones and nanocapsules. The former melt at wavelengths of 1100 nm, and the latter melt at 800 nm. The researchers believe this technique can be used for treating cancers.

At Rensselaer Polytechnic Institute (RPI), researchers are studying the magnetic behavior of nano materials that could lead to selective-drug delivery components. They devised a process for creating a single-walled CNT embedded with cobalt nanostructures 1 to 10 nm wide.

The electrical conductance of CNTs is sensitive enough to detect and be affected by trace amounts of magnetic activity, such as those present in the embedded cobalt structures. The researchers believe this is the first demonstration of the detection of magnetic fields of such small magnets using individual CNTs.

See associated figure

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