Berkeley engineers say its built smallest volume, most efficient wireless nerve stimulator

2 mins read

In 2016, University of California, Berkeley, engineers demonstrated the first implanted, ultrasonic neural dust sensors, bringing closer the day when a Fitbit-like device could monitor internal nerves, muscles or organs in real time. Now, it says it has taken neural dust a step forward by building what it claims is the smallest volume, most efficient wireless nerve stimulator to date. 

According to the team, its ‘StimDust’ device adds ‘more sophisticated electronics to neural dust without sacrificing its tiny size or safety'.

The aim is to have StimDust implanted in the body through minimally invasive procedures where it can monitor and treat disease in a real-time, patient-specific approach.

StimDust is 6.5mm3 in volume and powered wirelessly by ultrasound, which the device then uses to power nerve stimulation at 'an efficiency of 82%'.

"StimDust is the smallest deep-tissue stimulator that we are aware of that's capable of stimulating almost all of the major therapeutic targets in the peripheral nervous system," says assistant professor Rikky Muller of Berkeley. "This device represents our vision of having tiny devices that can be implanted in minimally invasive ways to modulate or stimulate the peripheral nervous system, which has been shown to be efficacious in treating a number of diseases."

The engineers believe its creation has opened the door for wireless communication to the brain and peripheral nervous system through tiny implantable devices inside the body that are powered by ultrasound. In fact, according to Berkeley, engineering teams around the world are now using the neural dust platform to build devices that can be charged wirelessly by ultrasound.

The team explains that it designed a custom integrated circuit to transfer ultrasound charge to the nerve in a well-controlled, safe and efficient way. This resulted in a stimulator able to wrap around a nerve cuff and record, transmit and receive data.

The components of StimDust include a single piezocrystal, which is the antenna of the system, a 1mm integrated circuit and one charge storage capacitor. The device has electrodes on the bottom, which make contact with a nerve through a cuff wrapping around it.

The team adds that it also built a custom wireless protocol that gives a large range of programmability while maintaining efficiency. The entire device is powered by 4µWand has a mass of 10mg.

After testing StimDust on the benchtop, the research team implanted it in a live rodent to test it in a realistic environment. Through a cuff around the sciatic nerve, the research team says it was able to control hind leg motion, record the stimulation activity and measure how much force was exerted on the hind leg muscle as it was stimulated. The researchers then gradually increased stimulation and mapped the response of the hind leg muscle to find out exactly how much stimulation was needed for a desired muscle recruitment.

The hope is that this work could be used to help treat diseases such as heart irregularities, chronic pain, asthma or epilepsy.

"One of the big visions of my group is to create these very efficient bidirectional interfaces with the nervous system and couple that with intelligence to really understand the signals of disease and then to be able to treat disease in an intelligent, methodical way," Muller explains. “There's an incredible opportunity for healthcare applications that can really be transformative."