Scholar Spotlight: Using Nano Technology, Amay Bandodkar Creates Self-Healing Wearable Devices

Wearable technology has increasingly found its way into consumers’ lives, with the fitness tracker Fit Bit and smart watches like the Apple Watch leading the market.

In the future, we can expect to see more such wearable devices—including thin, small, flexible, sensors that adhere to the skin. Nano engineers have been creating prototypes of these sticker-like sensors that could have dozens of health care, consumer, and military applications.

Existing technologies present barriers to the practicality of the prototypes, however: They can tear easily, and their thin profile makes the use of batteries impractical. Nano engineer and Siebel Scholar Amay Bandodkar (University of California San Diego, BioE ’16), has devoted his research to overcoming these limitations.

As a doctoral student in the research lab of Dr. Joseph Wang at the Department of NanoEngineering at the University of California San Diego, Bandodkar worked on developing wearable devices that can sense chemicals and devices that can harvest energy from human sweat.

He also helped pioneer a breakthrough technology that enables wearable devices to heal themselves using magnetic particles. His team published an article describing the discovery in the November 2, 2016 issue of Science Advances.

Now a postdoctoral fellow at Northwestern University, Bandodkar is continuing his research on wearable chemical sensors. He is also researching implantable devices for monitoring brain activity. He is especially interested in developing devices for biomedical applications, such as monitoring ICU patients and people who have just undergone surgery.

Bandodkar spoke with the Siebel Scholars program about wearable devices, his research at Dr. Wang’s lab, and the new paths he’s forging at Northwestern.

Q: What will wearable electronic devices look like in the future?

In the very near future, wearable devices will conform to the skin. Think of a very thin, flexible, patch that you apply directly to the body, and which moves and breathes with the skin. The user won’t even feel its presence.

These devices will monitor an array of vital parameters, such as glucose levels, electrolytes, heart rates, temperature, and stress levels. Multiple sensors on the body will interact, sending each other information, and to sensors on other people.

Right now, for instance, a pregnant woman needs to see her gynecologist to know the status of her baby and her own health. A wearable or implantable system could continuously monitor the health of the mother and baby and wirelessly transmit that information to the hospital or clinic without the need for a doctor’s visit.

In a military application, sensors placed on soldiers can keep a commanding officer updated on soldiers’ fitness levels. This information can help inform decisions about who needs a break in the action. For people with diabetes, sensors could track glucose levels and make needle prick tests obsolete.

Q: Your research on self-healing devices has undergone a few iterations. What steps did you take before you got to this latest breakthrough?

Wearable devices can be expensive to make, but printing them can significantly drive down the cost. So this has become an attractive approach. Printed, wearable devices move with the user’s body—they bend, stretch, and twist. But they usually break when they experience mechanical stress. We wanted to incorporate self-healing systems to extend the lifespan of these devices.

The first approach we took was to disperse microcapsules filled with organic solvents within the device. Where damage happened, the capsules broke and released the solvent, which helped form a bridge across the cracks. Within a few seconds you got conductivity and could use the device again. This had two problems: First, you can’t use non-bio compatible solvents for wearable devices. Second, the solvent evaporates over time, limiting the lifespan of the device.

Other research groups have used self-healing polymers and other chemistries to initiate the self-healing process. Those approaches require that you manually trigger self-healing by exposing the device to heat or UV light and leave it for several hours or days. These systems are also very sensitive, so under certain weather conditions, they won’t perform.

Q: How has your research overcome these limitations?

We came up with the idea of using magnets. Magnets attract each other. They are very inexpensive. And they will work under just about any weather condition.

We literally bought magnets at the supermarket, then ground them down into very fine particles and infused the ink with them. That worked. When the device split or broke, the magnetic particles attracted each other and it self-healed automatically, over and over. This is what we reported on in Science Advances.

You can the self-healing process in action in this video.

Q: All of these devices need power. Your research has helped devise novel ways to harness electricity. Tell us about that.

The groups I worked with at Dr. Wang’s laboratory and at Northwestern are both exploring ways to circumvent the need for batteries. The problem with batteries is that they discharge and are bulky. During my Ph.D., I worked on developing wearable biofuel cells that can scavenge energy from human sweat. We recently demonstrated that such a system can power LED lights and even a Bluetooth device.

One of the biggest challenges is optimizing the ink composition—finding the right balance of magnetic material, binder, and electric system components. If you put in too much magnetic material, the amount of the other components you can add decreases. There is a fixed amount of solid materials that can be suspended in a polymeric binder system. All of this material affects printability as well.

Q: Where is your research headed?

In my present lab, I am working on implantable devices that can monitor neurochemicals to measure brain activity as well as wearable non-invasive chemical sensors for fitness and health care applications.

I am currently exploring integrating near-field communications (NFC) technologies—the kind used for applications such as Apple Pay—into wearable patches to overcome the need for batteries. The patch will have a small antenna on it. When you tap your phone on it, the device will transmit information to your phone such as your glucose and sodium levels, temperature, and sweat rate.

Q: What inspired you to become a nano engineer?

I have always been interested in doing research. Every day offers a new challenge. I find it much more exciting than the prospect of a 9-5 job. Growing up in Mumbai, India, I knew I wanted to do my Ph.D. in the United States.

I began my graduate studies in 2011, not long after researchers had begun developing wearable devices. I wanted to be involved in the budding nano field. I was really excited to see how we could make chemical devices and sensors that could be integrated on wearable platforms.