Sense and Treat

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This story is from the 2026 issue of Discoveries, a UC San Diego Health Sciences magazine.

Imagine wearing a small patch on your arm capable of continuously measuring five or even 10 different biological signals, including medication levels, from the fluid that lies less than 1 millimeter beneath the surface of your skin. Now imagine this same patch automatically administering medicine directly into your body based on these real-time data streams.

A closed-loop sense-and-treat system like this may improve quality of life for people with diabetes and Parkinson’s disease. It may help identify septic shock — very early — in people admitted to emergency rooms. And that is just the start of what might be possible, thanks to collaborative efforts of combined engineering and medical teams at UC San Diego.

Lab under the skin: Microneedles

At the center of these efforts is a minimally invasive wearable sensing platform — and the engineering team led by Chemical and Nano Engineering Professor Joseph Wang, DSC, that is creating it.

“We are developing a lab just under the skin,” said Wang.

The key to this vision for a lab beneath the skin are tiny structures called microneedles — elements that can be designed as real-time biological sensors or as conduits for drug delivery. The sensing microneedles, each less than one millimeter in length, are designed to sense biomarkers or medicines of interest just beneath the surface of the skin, specifically in the body’s dermal interstitial fluid.

While closed-loop systems based on dermal interstitial fluid are not yet available, significant progress is being made. Efforts to clinically validate the real-time wearable sensing capabilities that will be fundamental to these kinds of systems, for example, are underway at UC San Diego.

For the last 15 years, the Wang lab has developed multiple microneedle designs of various shapes and functionalities. The microneedles that are currently in preliminary clinical trials at UC San Diego for real-time sensing of interstitial fluid are solid microneedles. They are coated with enzymes that bind to the biomarker or medicine of interest. The binding ultimately triggers an electrical signal that is recorded. The higher the concentration of a biomarker or drug, the larger the electrical signal. In future sense-and-treat systems, these solid microneedles will do the sensing. They will work in concert with hollow microneedles that deliver medication stored in reservoirs outside the body into the interstitial fluid. From there, the medicine will enter the person's bloodstream.

“We have made tremendous technical advances over the years, and we are now in an exciting clinical validation phase. At the same time, we continue to advance on multiple technical fronts, always keeping in mind our vision for minimally invasive closed-loop wearable systems combined with wearables for vital signs.

“Our goal is to improve the lives of as many people as possible,” said Wang, who is the SAIC Endowed Chair Professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the UC San Diego Jacobs School of Engineering.

Lab under the skin: Shallow multiplex sensing

For the general public, a common point of comparison for these microneedle-based wearable sensors of tomorrow are the continuous glucose monitors that are currently on the market.

One of the key differences is that the microneedle-based wearable sensor systems in development at UC San Diego have been designed as a platform technology for continuous monitoring of multiple biomarkers simultaneously. Today’s glucose monitors, in contrast, measure just glucose.

“Each microneedle is its own sensor, and on a centimeter square patch, there is room for many microneedles, each sensing a different biomarker or drug,” explained Wang, who co-directs the Center for Wearable Sensors at the Jacobs School of Engineering.

Another difference between microneedle-based sensor patches and the glucose sensors available now is the depth of the interstitial fluid being sampled. The new systems access the dermal interstitial fluid just below the skin via microneedles that are less than 1 millimeter in length. This interstitial fluid is shallower than pain nerves. This means that when microneedles pierce the outer layer of the skin to access this fluid, there is no pain and no feeling of a pin prick — just a bit of pressure.

In contrast, the continuous glucose monitors currently on the market measure interstitial fluid that is significantly deeper than 1 millimeter beneath the skin. To access this deeper fluid, today’s glucose sensors rely on a larger guide needle that usually goes 5 to 6 millimeters into the fatty tissue.

Clinical validation: Parkinson’s disease

With the goal of improving personalized care for people living with Parkinson’s disease, UC San Diego clinicians and medical researchers are collaborating with Professor Wang and his engineering team to further develop and test microneedle-based wearable patches that monitor medication levels.

Working together, they are developing comfortable, durable sensing systems that enable continuous monitoring of levodopa and other Parkinson’s disease medications.

Levodopa is the most effective medication for symptomatic treatment of Parkinson’s disease. It serves to replace dopamine and helps improve mobility and daily functioning. However, levodopa therapy is complex. The quantity and timing of medications depend on each person’s symptoms, which can vary between and even within individuals. Further complicating treatment, as Parkinson’s disease progresses, the patient’s response to medication can change, often leading to disabling and unpredictable fluctuations in Parkinson’s disease symptoms associated with rising and falling medication levels.

Currently, levodopa dosing adjustments are based on brief clinic assessments of the patient’s condition, which may not accurately reflect their fluctuating symptoms. Traditional methods of monitoring levodopa levels in blood plasma are costly, time-consuming and require centralized laboratory infrastructure, and are not used in clinical practice.

“Accurate, real-time drug monitoring could enhance the effectiveness of personalized management of Parkinson’s disease,” said Irene Litvan, MD, the Tasch Endowed Professor of Neurology in the Department of Neurosciences at UC San Diego School of Medicine and director of the school’s Parkinson and Other Movement Disorders Center.

Litvan is leading an ongoing pilot clinical trial at UC San Diego in collaboration with Wang to test a minimally invasive, wearable sensor device that monitors levodopa levels in real time. This clinical trial is evaluating the accuracy, tolerability and safety of the microneedle-based device in people with Parkinson’s disease.

The team’s collaborative efforts are part of a larger goal to create an automated system that measures these medication levels continuously and uses that information for automated medication delivery through the skin by way of microneedles.

The team is also working on systems to monitor levodopa in sweat and capillary blood, which is blood sampled through quick, minimally invasive finger pricks that patients can perform themselves. But in terms of the future vision of a set-and-forget wearable patch that administers the right medication dose at the right time, a microneedle-based patch is especially attractive, the clinicians said.

Having a wearable device you place on your arm and don’t have to worry about or manually interact with is an important design feature, explained Katherine Longardner, MD, a practicing neurologist at UC San Diego Health and assistant clinical professor in the Department of Neurosciences at the School of Medicine, who is collaborating with Litvan on this work. “If you have motor symptoms, you don’t want to keep fiddling with the device throughout the day.”

Lactate sensing in the emergency department

Another UC San Diego collaboration is focused on assessing the performance of a microneedle-based wearable system that continuously measures lactate levels. These sensing systems are being clinically validated thanks to patient-volunteers with serious medical conditions at UC San Diego Health.

In a study published in 2026 in ACS Sensors, the researchers reported that the wearable microneedle-based continuous lactate sensors were highly accurate compared with standard blood tests for people in a variety of hospital settings, including an intensive care unit and an emergency department.

The prospect of access to continuous, real-time lactate levels in people in intensive care units and emergency departments is of great interest to physicians. Rising lactate levels signal a lack of oxygen in the blood, and reliable real-time measurements of lactate in interstitial fluid may help physicians detect early signs of sepsis or shock, which in turn can lead to better patient outcomes and potentially save lives.

But recognizing early on that lactate levels are rising is difficult to do right now because each check requires a separate blood draw, which can lead to anemia in patients. Frequent blood draws are also uncomfortable and contribute to rising health care costs.

“The lactate microneedle electrode has the strong potential to allow us to risk stratify patients in real time and to assess their responses to therapy. We are working toward an approach where we can use real-time lactate measurements to guide use of IV interventions to stabilize blood pressure and protect vital organs, eventually to individualize sepsis therapy. The microneedle electrode is well tolerated and gives stable and accurate results in our studies to date,” explained Atul Malhotra, MD, professor at the School of Medicine and pulmonologist and research chief of Pulmonary, Critical Care, Sleep Medicine and Physiology at UC San Diego Health.

Continuous sensing: A new AI-powered era

This wearable sensing platform is one of many technologies generating new kinds of continuous health-related data streams that individuals and physicians can soon have access to — both at home and in hospitals or other health care settings.

Understanding how individual patients, physicians and entire health systems can best use continuous data streams — some of which are already here — is hugely important.

AI, data science, engineering, and privacy and security are all critical to the conversation. Closed-loop sense-and-treat systems for diabetes or Parkinson’s disease, for example, can leverage AI as well as advances in integration with ultra-low-power electronics, wireless communications and systems that monitor vital signs, such as heart rate, skin temperature and blood pressure.

To create life-improving solutions that scale, UC San Diego teams are both pursuing clinical validation and also studying how new data streams and the platforms that generate them fit into today’s complex health care regulatory and financial environments.

“On their own, neither clinicians, engineers nor data scientists can develop technologies to advance medicine and human health,” said Sam Ward, PT, PHD, vice dean for research in the School of Medicine. “But working together, we can arrive at new insights and new kinds of actionable information. This is the power of the close proximity between a world-class engineering school and a world-class school of medicine and health system.”

Ward is a UC San Diego faculty member with appointments in orthopedic surgery, radiology and bioengineering. His research team is collaborating with the Wang lab on efforts to study how microneedle patches may be useful for optimizing human performance. The team recently published the first work demonstrating that the microneedle-based wearable sensor patches can be used to accurately monitor lactate levels in baseball pitchers.

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