Sensing technology that could save life and limb

Dr. Vamsy Chodavarapu, founder of Sharp Microsystems and Director of McGill’s Sensor Microsystems Laboratory

Long used to keep track of everything from packages to pets, Radio Frequency Identification (RFID) now offers the potential to address a hard-to-diagnose, life-threatening condition.

Acute Compartment Syndrome (ACS), caused by traumatic injury, can have devastating effects on the human body. High-energy impact causes swelling and increased pressure within the muscle compartments that reduces blood flow, leading to oxygen and nutrient deprivation to the injured area.

The current method of diagnosis, which uses a physical exam and repeated needle pricks over a short timeframe, is inadequate for continuous pressure monitoring. Without rapid identification and timely and appropriate treatment, ACS may result in severe pain, paralysis, sensory deficits and even amputation.

Patients at greatest risk are those in traumatic situations such as accidents, natural disasters or war zones, where diagnosis is difficult because patients often have multiple trauma and may be confused, distracted and not fully responsive.

A better treatment option is on the horizon, however, thanks to an advanced sensor microsystem recently developed by Dr. Vamsy Chodavarapu of McGill University in collaboration with Dr. Edward Harvey at Montreal General Hospital. Dr. Chodavarapu, an associate professor in Electrical and Computer Engineering, has devoted his career to studying and understanding instrumentation, measurement, sensor technologies and sensor signal processing, and applying this knowledge to the fields of chemistry, biology and medicine.

One of the results of these explorations has been the development of a tiny, injectable silicon-based wireless sensor. The device combines an integrated circuit based on a commercial RFID transceiver and a proprietary capacitance-to-digital converter, with a micro-electro-mechanical systems (MEMS) absolute capacitive pressure sensor, making it possible to continuously measure pressures in the limbs of patients at risk of developing ACS.

“It’s very difficult to get information from the deeper compartments of the limbs,” says Dr. Chodavarapu. Early testing has shown his removable device to be capable of being inserted into difficult-to-access areas, and simple enough to be administered even under extreme environments such as trauma scenes or field hospitals. “It wouldn’t interfere with the movement of patients during stabilization, surgery or intensive care,” Dr. Chodavarapu says. “It could revolutionize the care of trauma victims, and minimize the devastating effects of this syndrome.”

As Director of McGill’s Sensor Microsystems Laboratory, Dr. Chodavarapu regards this kind of acute care procedure as a promising outcome that has been made possible because of rapid advancements in sensing technologies for medical applications. This versatile RFID platform technology is now being extended to wireless, batteryless chemical and biological sensors for applications in food storage and safety, athlete performance and safety, and prosthetic joint health monitoring.

“What I have been able to establish at McGill is a very fruitful collaboration with other researchers, including clinical researchers,” he says. “Health care is one of the leading applications that my lab focuses on.”

Other fields being investigated include monitoring of fresh water resources and fish ecology. He has developed sensor interfaces for implantable acoustic telemetry tags now licensed by Vemco, a Nova Scotia firm that specializes in remote monitoring of fish, to track their geographic position and water quality. The company is now interested in using the technology to monitor dissolved oxygen concentration, pH, and and potentially other properties.

All of this work has provided the basis for his Montreal-based startup company, Sharp Microsystems, which specializes in sensor systems as well as MEMS design services. He notes that while design-only CMOS service is a well-established business, the market for MEMS design work is just starting to open up, and Sharp is among the forerunners in this niche.

Much of Sharp’s progress has been achieved because of cost-effective access to equipment and expertise for prototyping provided by CMC Microsystems, he says. These include powerful MEMS design capabilities, including the ANT NanoSOI process, Micralyne MicraGEM process, University of Waterloo UW-MEMS process, and Teledyne DALSA MIDIS process.

“CMC provides us with fabrication access to various state-of-the-art processes for CMOS and MEMS, which are not easily available to researchers in most other countries,” he says. “If you have to invest in this infrastructure yourself, your company can’t take off.” The resources made available by CMC have enabled Dr. Chodavarapu to pursue an innovative idea and an ambition that might otherwise have been unattainable.

“Trying to provide design and contract development for MEMS would be a unique service that could also be offered,” he says. “That’s what I’m trying to do with this company.”

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