A Step in the Right Direction

Whether they are caused by Parkinson’s disease, stroke, or injury, balance issues are a huge risk to the wellbeing of those that experience them. Falls that result from imbalance can have devastating consequences, especially for older adults. There are millions of fall-related hospitalizations each year, and the impacts range from hip fractures and traumatic brain injuries to death. These problems are compounded as many health systems are overwhelmed and cannot give sufficient attention to those at risk of falls, so new solutions in this area are sorely needed.

Fortunately, help may be on the way. A group of researchers at Georgia Tech has created an inexpensive wearable device that slips into a shoe to diagnose balance disorders and assist medical professionals in better treating them. The inserts are manufactured using a process that is already well established in the electronics industry, so if this system proves itself to be valuable beyond the research lab, it could easily be mass produced.

The new device is a thin, flexible insole lined with 173 piezoresistive sensors. These sensors, screen-printed directly onto a flexible circuit board using carbon-based nanomaterials, measure plantar pressure — that is, the distribution of force across the bottom of the foot during movement. This is a vital metric for identifying imbalances in gait that often precede falls. Traditional gait analysis systems require bulky equipment or can only be used in clinical settings. By contrast, this lightweight insole works wirelessly and can be worn during everyday activities, offering a continuous stream of data.

Alongside the sensor array, the device integrates a compact data acquisition system and a Bluetooth Low Energy communication circuit. This small module is housed in a discreet case mounted at the heel, minimizing any disruption to natural walking. Data is transmitted wirelessly to a smartphone, where it can be logged, visualized, or even combined with machine learning algorithms to detect early warning signs of instability. The high density of the sensors makes it possible to track subtle shifts in weight distribution, pinpoint the center of pressure, and analyze different phases of the gait cycle.

In experimental trials with healthy volunteers, the device demonstrated the ability to deliver accurate, real-time plantar pressure data under normal daily conditions. The researchers now plan to expand testing to patients with gait impairments, such as those recovering from stroke or living with Parkinson’s disease. They also envision potential applications that extend beyond medicine in the future. Athletes could use the insole to optimize performance, for instance.

Other competing technologies exist for plantar pressure sensing, such as those that use capacitive or optical sensors. But each has limitations — whether in durability, accuracy, or comfort — that have hindered their adoption to date. By choosing piezoresistive sensing with a custom carbon-epoxy-elastomer ink mixture, the team achieved both high sensitivity and robustness. Combined with the affordability of this technology, that might be enough to make it a winner.