For anyone living with bipolar disorder, lithium is a lifeline to a better quality of life. As a result, it remains the gold standard in treatment, tamping down wild emotional swings and curbing suicide risk.
But it’s far from an easy fix. Psychiatrists must walk a narrow therapeutic tightrope when prescribing the drug. Too small a dose, and symptoms threaten to return. Too large a dose, and that patient runs the risk of toxicity, and the nausea, tremors, and possibly even permanent neurological damage that it entails.
Until now, maintaining that delicate balance has meant frequent blood draws and lab visits. It’s not just inconvenient. It’s an invasive ritual that challenges the patience of even the most vigilant patients.
But there might be a better way. A new wearable device might offer a more “user friendly” alternative.
University of Southern California researchers have announced that they’ve built a soft, skin-conforming sensor patch that continuously monitors lithium levels in sweat. And the wireless system doesn’t just track lithium levels with uncanny accuracy. It also links to a smartphone app for real-time updates.
“Our goal was to create an easy-to-use sensor that bypasses the need for blood draws entirely,” explained Yasser Khan, a USC Ming Hsieh Department of Electrical and Computer Engineering professor who leads the USC Khan Lab.
The Secret Ingredient(s)
And the secret ingredient? The WLS-OECT: a clunky acronym (wearable lithium-sensitive organic electrochemical transistor) that could mark a turning point in psychiatric care.
A lithium-selective sensor, cobbled together with printed organic electronics, makes up the heart of the WLS-OECT. Unlike traditional electronics, which rely on rigid silicon, the USC scientists built this system from flexible materials that they then printed directly onto a plastic substrate using inkjet and 3D printing techniques.
The result? A soft, stretchable device that sticks comfortably – and securely – to the skin.
The patch contains several crucial components:
- A microfluidic channel that collects sweat.
- A sensor that detects lithium ions.
- And custom-designed electronics that relay readings to a smartphone app via Bluetooth.
It even includes a mini sweat induction system that uses iontophoresis – a small electrical current and a chemical agent called pilocarpine – to stimulate sweat production on demand. This enables the sensor to gather just enough fluid for analysis without the need for physical exertion from the wearer.
“We developed the entire lithium monitoring system—from the OECT-based sensor patch and on-demand sweat induction to the readout electronics and smartphone app—using a simple, scalable, and cost-effective fabrication process,” PhD student and first author Mohammad Shafiqul Islam explained. “Our goal was to make lithium tracking as easy and comfortable for patients as checking a daily fitness tracker.”
From Bench Tests to Trial Runs
The lithium-detecting sensor operates by monitoring current changes as lithium ions interact with a conductive polymer channel. A special membrane ensures the sensor only responds to lithium, ignoring similar ions found in sweat, such as calcium, potassium, and sodium.
In lab tests, the sensor showed impressive stability, selectivity, and reversibility. It maintained accuracy across repeated uses, could distinguish between different lithium concentrations, and responded consistently even after 100 test cycles.
To account for variations in manufacturing, the researchers devised a calibration method that relies on the ratio of current changes instead of the absolute current.
But the USC team didn’t stop there. They tested the patch on three healthy volunteers and three individuals receiving lithium therapy for bipolar disorder. Participants wore the patch on their forearms, and the smartphone app triggered the sweat stimulation process. Over 20 minutes, the device constantly monitored the participants’ lithium levels.
Among the healthy participants, the patch registered stable levels near 0.1 mM. Conversely, the patients on lithium regimens showed sweat concentrations between 0.6 and 1.5 mM, accurately reflecting their documented dosages. Readings from the patch also lined up with those from a commercial lithium sensor, confirming its viability – and reliability.
What It Means
By removing the need for repeated lab visits, the WLS-OECT could dramatically ease the burden of lithium monitoring. For patients, it means more freedom and fewer disruptions. And for clinicians, it paints a clearer picture of medication adherence and physiological response, paving the way for tailored – and more responsive – care.
While the USC crew designed this version for home use, future iterations could integrate seamlessly into clinical workflows, allowing psychiatrists to monitor their patients remotely and intervene quickly when levels start to drift.
In a field where treatment breakthroughs are rare and the stakes are high, this patch represents a rare convergence of biology, engineering, and empathy—a small device with the potential to make a big difference.
Further Reading
A New Tool to Refine Lithium Therapy
Rates of Major Depressive Disorder and Bipolar Disorder in Black and White Postpartum Women
