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Sensing and Estimation: Rajesh Rajamani

Mechanical engineering professor Rajesh Rajamani’s research specialty is focused on electromechanical sensors that have medical or automotive applications. “I work on sensing and estimation systems,” he said. “We build prototype sensors and develop estimation algorithms that can provide estimates of variables that you want to track in real time.”

One of his many projects currently in commercial development with a business partner is supported by MnDRIVE funding. However, because it’s still in the development stage, it’s one which he cannot speak freely about beyond explaining that it involves using measurements of magnetic fields to estimate the position of ferromagnetic—steel and iron—objects.

Though the project will have biomedical applications, Rajamani said, “We are looking at the mechanical applications right now, in particular its use for measuring piston positions in industrial equipment and mobile applications.”

“Measuring elasticity can be used for diagnosing tissue health in many applications. For example, with precise data, you can differentiate between tissues that have tumors and those that don’t.”

–Rajesh Rajamani

Among his other projects, Rajamani and his colleagues have licensed technology to a Minnesota startup called FocusStart. In this project, they have developed a handheld device to measure tension in the body’s taut soft tissues. The device could have a revolutionary impact on orthopedic surgery, in particular for joint replacement surgery that is becoming increasingly common as the country’s population ages.

In a nutshell, the FocusStart instrument will allow surgeons to measure tension in soft tissues quantitatively rather than by “feel.” In turn, this will ensure bones and replacement joints align exactly, greatly reducing the wear of implant devices and improving the functionality of the replacement joint.

For instance, during knee replacement surgery, the probe would be used to measure and balance tension in the knee ligaments, leading to good restoration of knee function and a long lasting implant. Likewise, during hip replacement surgery, the probe would be used to measure tension in the abductor muscles to ensure the hip prosthesis is in balance and has the right amount of normal force to prevent both hip dislocation as well as uneven gait.

Another of Rajamani’s patent applications involves an NIH-funded project for a urethral catheter capable of accurately measuring distributed urethral pressure at several different points simultaneously, while also measuring EMG signals, even while a patient is moving. Currently catheters can only measure pressure at one point in the urethra, and a patient must remain still during urodynamic tests. Especially in female patients, Rajamani’s instrument will make it possible for urologists to pinpoint the exact source of incontinence, whether muscular or neurological, and treat the problem without guesswork.

Yet another of his projects—this one undergoing in vitro testing—is a flexible MEMS sensor that measures tissue elasticity.

“wor elasticity can be used for diagnosing tissue health in many applications,” Rajamani explains. “For example, with precise data, you can differentiate between tissues that have tumors and those that don’t. It could be used, for instance, to measure the health of knee cartilage during minimally invasive surgery, or to measure the pressure inside a compartment that the instrument is pushing against.”

Rajamani came to the University of Minnesota from the University of California-Berkeley in 1998 where he specialized in estimation and control for mechanical applications. His expanded interest in biomedical applications comes as no surprise to anyone familiar with Minnesota’s technological leadership—a leadership reflected in the MnDrive initiative itself.

“When I came here, I saw a lot of collaboration between the University of Minnesota Medical School, the College of Science and Engineering, and industry,” he said. “Sensing and biomedical applications really took off for me after coming to Minnesota.”