University of Southern California researchers have developed a groundbreaking ultrasound device that could reduce reliance on addictive painkillers for patients with chronic pain
Chronic pain affects a vast population across the world and is a debilitating condition that impacts quality of life. Painkillers are used to treat chronic pain, but they can be highly addictive. However, a new device created by USC biomedical engineers could help patients avoid the need for opioids and manage their conditions effectively. The research is published in Nature Electronics.
AI wireless implant for personalised chronic pain management
Currently, implantable electrical stimulators offer an alternative by stimulating the spinal cord to block pain signals from reaching the brain. However, these devices have high costs, involve invasive surgery and require frequent battery changes.
Researchers from the Zhou Lab in USC Viterbi’s Alfred E. Mann Department of Biomedical Engineering, in collaboration with the Jun Chen Group at UCLA, have developed a revolutionary solution for chronic pain: a flexible ultrasound-induced wireless implantable (UIWI) stimulator secured to the spine and designed for personalised, self-adaptive chronic pain management.
The pioneering chronic pain device is designed to bend and twist with movement and is powered by a wearable ultrasound transmitter without the need for a battery. The design eliminates many of the common complaints about current spinal cord stimulators. Additionally, the new device uses machine learning algorithms to customise treatment individually.
The future of personalised pain management
The chronic pain implant converts mechanical waves into electrical signals through a phenomenon called the piezoelectric effect. The core of the UIWI stimulator is a miniaturised piezoelectric element made from lead zirconate titanate (PZT), a highly efficient material for converting incoming ultrasound energy into the electrical power needed for stimulation.
“What truly sets this device apart is its wireless, smart and self-adaptive capability for pain management,” Professor Qifa Zhou said. “We believe it offers great potential to replace pharmacological schemes and conventional electrical stimulation approaches, aligning with clinical needs for pain mitigation.”
PhD candidate in the Zhou Lab and lead author Yushun (Sean) Zeng said the wireless, innovative, miniaturised stimulator could produce sufficient electrical stimulation intensity using ultrasound energy, resulting in a more personalised, targeted, and localised treatment.
“This energy-converting type is critical for deep stimulation, as ultrasound is a non-invasive and highly penetrating energy in clinical and medical areas,” Zeng said. “By leveraging wireless ultrasonic energy transfer and closed-loop feedback system, this UIWI stimulator removes the necessity for bulky implanted batteries and allows for real-time, precisely adjustable pain modulation.”
“From a clinical standpoint, incorporating deep learning–based pain assessment enables dynamic interpretation and response to fluctuating pain states, which is essential for accommodating patient-specific variability,” added Zhou Lab PhD candidate Chen Gong, also a lead author on the paper.
The device operates by continuously monitoring brain recordings, specifically electroencephalogram (EEG) signals, to detect chronic pain. The machine learning model, based on a neural network called ResNet-18, analyses the brain signals and then classifies the pain into three distinct levels: slight pain, moderate pain, and extreme pain. This AI model achieves an overall accuracy of 94.8% in distinguishing between these pain states.
Once the pain level has been identified, the wearable ultrasound transmitter automatically adjusts the acoustic energy it transmits. The UIWI stimulator can then sense the propagated energy and convert it into electrical intensity, stimulating the spinal cord. This creates a closed-loop system that provides real-time, personalised pain management.
The Zhou Lab team tested the UIWI stimulator in rodent models, with results demonstrating its effectiveness for pain management. Lab tests showed that treatment from the UIWI stimulator led to significant reductions in pain indicators. In one experiment to evaluate whether an animal associates an environment with pain relief, rodents showed a clear preference for the chamber where the pain management system was activated, further confirming the device’s effectiveness. Researchers successfully relieved chronic neuropathic pain caused by both mechanical stimuli (like a pinprick) and acute thermal stimuli (infrared heat).
“Our findings highlight the potential of ultrasonic implantable electronics in clinical and translational chronic pain management,” Zeng said.
