Tomorrow's Health, Today's Research

Nikolai Dechev

Associate Professor, Department of Mechanical Engineering
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Phone: 250-721-8933
Laboratory Page

Research areas: biomedical systems design, robotics and automation, mechatronics and machine design

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Research Profile:

Listening to Ligaments: Biosensors that can detect our desire to move, implantable devices that use wireless power transfer and the future of prosthetics

 

Dr. Nikolai Dechev is an associate professor of mechanical engineering at the University of Victoria and, currently, Director of the Biomedical Engineering Program. The majority of his research centers on electro-mechanical systems design and its application to biomedicine.

Biosensors. One of Dechev’s research projects focuses on designing novel sensors that are capable of detecting body signals. “We’re trying to detect a human being’s desire to move their body,” says Dechev. “The hypothesis is that if someone wants to move their hand, there will be movement of their tendons, so how can we measure that movement?”

Dechev’s team has developed a portable, non-invasive, ultrasound-based sensor system for advanced prosthesis control. Led by postdoctoral fellow, Dr. Stegman, the team has shown that an ultrasound transducer positioned on the surface of a persons’ wrist is capable of accurately measuring internal tendon movements.

 In collaboration with Victoria-based hand surgeon, Dr. Slobodan Djurickovic, the team was able to verify the tendon tracking system during live carpal tunnel surgeries with 5 patients. Distinct ultrasound signals were, indeed, associated with specific tendon movements.

While research is still in the early stages, in theory, such an ultrasound biosensor placed just inside the socket of a prosthesis would be able to ‘read’ an amputees internal tendon movements and direct the appropriate output of a mechanical hand in order to execute the desired movement.

Ultrasound-based biosensors would be limited to specific types of amputations, those that still have functional tendons within the remaining stump. The primary barrier to making this innovative system a reality is figuring out how to modify a traditional ultrasound machine into a small, portable, battery-operated model.

Implantable devices. Dechev has also been working in collaboration with fellow UVic researcher, Dr. Kerry Delaney, a neurophysiologist who is researching brain plasticity and recovery from stroke. Tackling the engineering side of things, Dechev has been working to develop wireless power transfer technology in order to power miniature implantable sensors capable of measuring EMG and EEG signals in laboratory mice.

The implants rely on energy transfer from a transmitter coil to a receiver coil through oscillating electromagnetic fields. As long as the receiver coil, which is approximately the size of a dime and located within the implant, is contained within the electromagnetic field generated by the external primary coil, there is no need for time-limited batteries or cumbersome electrical wires.

Implantable sensors that are capable of measuring intra-muscular signals also have the potential to play an important role in advanced prosthesis control. Dechev, however, notes that so far no one has figured out how to overcome the most significant roadblock: the human body’s tendency to reject all foreign material inside it. As it stands, it takes just 9 to 12 months for an implant’s electrodes to become so cocooned in scar tissue that the signal becomes impossible to measure.

Continuous passive motion machine. Dechev has also used his robotics skills to design biomedical equipment, including a continuous passive motion (CPM) rehabilitation therapy machine. In collaboration with Dr. Ed Park, the team worked with the Island Hand Therapy Clinic to design and test the device.

Clinicians often spend a great deal of time engaging in what is referred to as continuous passive movement, a therapy that is grounded in the ‘use it or lose it’ concept. Repetitive, manual manipulation of a patient’s limb not only maintains joint flexibility but also keeps motor signals travelling up to the brain, hopefully stimulating the growth of new neural pathways. A single therapist might spend upwards of 40 minutes simply opening and closing a patient’s hand, prompting clinician Clare Faulkner to ask, “Can’t you make a machine that will do this?”

Dechev’s response was to develop a CPM machine that simulates a clinician’s hands-on techniques. Designed with adjustable torque-limit controls, the CPM machine is capable of maintaining a therapeutic rotational force while limiting the possibility of injury through overextension/flexion of the joint.

The Victoria Hand Project: an affordable upper-limb prosthesis for the developing world. Dechev is also interested in the design and development of advanced lower arm prosthesis systems. While the majority of his work revolves around cutting-edge technologies — multi-channel output mechanisms and novel methods of user-control — he’s also not afraid to go back to the basics.

With the help of advanced 3D printing technology and a dedicated team of student volunteers, Dechev has succeeded in designing a simple mechanical prosthetic hand that is both functional and affordable. This prosthetic hand, the key to Dechev’s not-for-profit organization, the Victoria Hand Project, can be built and deployed to amputees living in developing countries, such as Nepal and Guatemala, for just over $300.

“This is where I actually get to apply my work to help people,” says Dechev. “It’s nice to see our efforts improving peoples’ quality of life.”