Triboelectric Generator to Power Smart Knee Implants

The word ‘smart’ in today’s world has to do with information technology and operating system. It is used in many fields of endeavor including medicine. IT-driven knee implants can soon become a treatment method, kudos to research carried out by a team that includes faculty at State University of New York and Bingham University

Knee replacement operation is the most dominant joint replacement technique. The number of surgeries has continued to increase year in year out. Many of the surgeries are carried out to replace a previously done surgery in the past. The numbers of these surgeries performed on younger and more active patients continue to soar. After the surgery, it is expected that they stay physically lively for their general health and well being. However, being active can wear out the new implant sometimes. Most times, doctors are not aware if patients are exerting too much pressure on themselves as this can affect the implant. They realize this only when they start to show some symptoms. At the time they do, the damage would have been done on the implant. It is a difficult one for a young patient who has to go through the procedure every five or ten years. Similarly, knowing the ideal balance of activity levels, to maintain the implant is equally a daunting task.

Based on the challenges above, researchers concluded it was time to come up with a smart knee implant that will effectively monitor changes in the activity of the patient. The lead principal investigator of the research was Sherry Towfighian, an assistant professor from Binghamton University. The study was done with strong support coming from the National Institutes of Health (NIH).

The team is working on a knee implant that comes with inbuilt sensors that are capable of monitoring the amount of pressure that is being exerted on the implant. This is in a bid for doctors to have a better knowledge of exactly the amount of activity that is negatively impacting the implant.

With the sensors, the doctors will be able to tell the patients the time a particular movement is in excess for the implant. This is intended to help the patient quickly adjust to prevent damage to the implant.

While the sensors solve one problem, they create another one. The sensors need energy to operate, but replacing battery in such a sensor is not possible. The researchers focused on a mechanism that is harvesting energy from friction during motion using triboelectric generator. Once a person walks, the microsurfaces of the generator rub against each other and create energy to power the sensor.

The design of the circuit was done by Emre Salman, an associate professor from the Stony Brook University. He calculated that the circuit will require a power of 4.6 microwatts. The initial test reveals that the power of six microwatts will be produced by an average person. This is even more than enough for powering the sensors. On this aspect of the study, Ryan Willing, an assistant professor at the University of Western Ontario complemented the team’s efforts.

The smart implants will both serve to assist scientists in future implant’s development and provide feedback to doctors on the state of the implant. With this knowledge, researchers will start to enhance the quality of the implant even more.

Professor Towfighian is optimistic that bringing together of activity sensors and the self-powered system is capable of extending the life of an implant and cut down the need to go for follow-up surgeries. For those young patients considering the possibility of surgery in knee replacement, this innovation has the ability to bring a new lease of life in knee replacement surgery.

Further information: Alwathiqbellah Ibrahim et al, A smart knee implant using triboelectric energy harvesters, Smart Materials and Structures(2018). DOI: 10.1088/1361-665X/aaf3f1