Thanks to technological advances, wearable devices are becoming increasingly integrated into our daily lives. While smartwatches are currently the most common form, did you know that in the near future, we may see revolutionary devices that are as soft as human skin and can seamlessly merge with the body?
At the core of making these next-generation devices a reality is the research and development of soft nanoelectronic materials. These materials make it possible to add electrical conductivity to soft, flexible substances like rubber or gel—materials that traditionally don’t conduct electricity. This breakthrough opens the door to entirely new types of wearables, such as bandage-like devices that stick to your skin, or ultra-thin sheets that can be applied to the face without being noticeable.
In this edition of Invent Innovation, our interview series featuring scientists working at the forefront of research, we spoke with Dr. Naoji Matsuhisa of the University of Tokyo’s Research Center for Advanced Science and Technology. He’s pioneering the development of interactive devices using soft nanoelectronic materials. We asked him about what sparked his research, what he’s currently working on, and his vision for a future where the line between humans and electronics disappears.
The Rise of Wearable Devices: What Does the Future Hold?
— Wearable devices are becoming increasingly popular as public interest in health grows worldwide. The market is expanding year after year. Do you personally use wearable tech, Dr. Matsuhisa?
Yes, I do. Right now, I’m wearing an Apple Watch.
— What do you find most beneficial about using wearable devices?
For me, the biggest advantage is in managing my schedule. I can be forgetful at times, so it’s incredibly convenient to quickly check upcoming appointments on my wrist. I also use it to monitor my sleep. There have been plenty of times when I’ve thought, “I don’t feel great lately,” only to check my Apple Watch and realize I haven’t been getting enough sleep. So, it really helps with managing those little details in my daily life.
— On the other hand, have you experienced any downsides to using wearable devices?
Right now, it’s cool out, so I haven’t had any problems. But in the summer, or when you go somewhere hot, the watch strap can cause skin irritation for some people. I used to live in Singapore as a research fellow, and I feel like in hot, humid climates like that, wearing something like an Apple Watch all day can be a bit uncomfortable. That’s why I think we really need wearable devices that are comfortable to wear even in high temperatures.
— Wearable devices are often depicted in anime and sci-fi movies in various forms—glasses, contact lenses, even devices embedded in the skin. Given the current pace of technological development, what kinds of devices do you think could realistically become a part of our lives in the near future?
Actually, devices like smart glasses and contact lenses are already starting to become practical. So rather than being part of some distant future, I think those kinds of wearables are just around the corner. That said, we still don’t know how readily society will accept them. To get these new types of devices to truly take hold, I believe developers—myself included—have a responsibility to actively demonstrate their potential through prototypes and work to gain social acceptance.
Developing Soft Electronic Materials
Creating Next-Generation Devices That Integrate with the Human Body
— To start, could you tell us about your research theme once again?
Our lab focuses on developing interactive devices using soft nanoelectronic materials.
Most wearable devices available today are compact and designed to be worn on specific body parts like the wrist, fingers, ears, or eyes. Why is that? The main reason lies in the fact that conventional electronics—smartphones, computers, and the like—are rigid by nature. While flexible smartphones have begun to appear recently, most components used in smartwatches and other devices remain hard and inflexible. That rigidity limits where and how comfortably people can wear them, which is why current wearables tend to be small and location-specific.
Our research aims to overcome this limitation by making devices—and the materials they’re made of—softer. Specifically, we’re developing new materials and electronics that are soft and stretchable. For instance, rubber is generally known to be non-conductive, but by mixing it with conductive materials like silver or carbon, or by altering its molecular structure, we’ve been able to create electrically conductive rubbers—even rubbery semiconductors. Using these materials, we design new kinds of electronics and develop soft, wearable devices.
The soft electronic materials we’re working with are as pliable as human skin. This allows us to create devices that can be applied directly to the skin like a bandage, or even adhere seamlessly to skin folds. Our goal is to develop wearables that are not only more comfortable to wear than existing products, but that truly integrate with the human body. That’s the vision that drives our day-to-day research.
— Is rubber the material you most commonly use for these electronic components?
Yes, that’s right. We also use gels in some cases. Gels are substances that contain a large percentage of water—things like agar or konnyaku (a jelly-like Japanese food) are good everyday examples. They’re soft and flexible, which makes them ideal for certain applications.
— What led you to choose soft electronic materials and interactive devices as your main research theme?
Honestly, the reason is pretty simple—I just thought “rubber that conducts electricity” was really cool.
You might remember doing experiments in school where you use a tester to check whether different materials conduct electricity. I always found that kind of thing fun. So I thought, wouldn’t it be interesting if I could make a material that I created myself stretch, shrink, and still conduct electricity? That idea really fascinated me, and that’s what led me to start this line of research during my university years. It all began with that simple curiosity.
Electronic Cosmetics and Invisible Sensors: A Look into the Latest Research
— Could you tell us about some of your latest research projects?
Lately, I’ve been working on a concept we call “e-cosmetics.” It’s a technology that uses a film—essentially a wearable display—that can be applied directly to the skin to achieve cosmetic effects similar to makeup.
We’ve already developed a working prototype, and are currently conducting experiments using a film that glows blue. With this technology, it’s possible to imagine makeup that responds to your surroundings—for example, your cheeks might flush red when you make eye contact with someone, or the color of your face could shift to match the environment.
I think it would be really exciting to create cosmetic tools like that, and that idea is driving this research forward.
— That’s a fascinating area of research. Are there any other themes you’re currently working on?
One project that’s relatively easy to explain involves the human face. The face is an incredibly rich source of biological information. For instance, from the forehead, we can measure brainwaves (EEG); around the eyes and cheeks, we can gather EOG (electrooculogram) data to track eye movements; and from the area around the mouth, we can collect electromyographic (EMG) signals that reflect muscle activity, which could even help predict what words a person is about to say.
Brainwaves, in particular, are important because continuous monitoring could help detect neurological conditions such as Alzheimer’s. That’s why we’re working on developing electrodes that can be worn on the face at all times—devices that are so subtle and comfortable that they’re visually unobtrusive and barely noticeable when worn.
Conceptual image of “unperceivable and invisible wearable electronics ” in use (courtesy of Professor Matsuhisa)
We’ve already succeeded in creating electrodes that are invisible to the eye and practically undetectable to the touch, even when worn on the face. Our next step is to collaborate with medical institutions to determine whether this kind of technology is truly needed in real-world healthcare settings.
In parallel, we’re also conducting more fundamental research. Recently, we developed a highly durable, conductive gel that can be stretched up to 10 times its original length without breaking. This kind of gel, which is as soft as tofu or human organs, has been gaining global attention in the field of electronics. We’re currently exploring how this new material might be applied in future projects.
New Ideas Born from Public Engagement
— You’ve appeared on YouTube programs and given public talks—you seem very proactive about sharing your research with the public. Why is that?
There are two main reasons. First, I believe that communicating research results is a way to give back to society—especially since much of our research is funded through public and institutional grants. Second, speaking to others helps refine and clarify my own thinking. That’s why I’m also very committed to outreach activities, including those aimed at junior high and high school students.
— Have these outreach activities brought you any particular insights?
Yes, quite a few. In our lab, we often give presentations and offer hands-on research experiences for students. During those interactions, I’m frequently asked, “What’s most important when doing research?” When I try to explain my core values in simple, clear language, it often leads to moments of realization—“Ah, yes, I suppose this really is something I value.” It helps me reflect and organize my thoughts.
It’s not just students, either. Sometimes, comments from members of the general public lead to new research ideas. For example, when I was a Ph.D. student working on stretchable conductors made with silver, someone once asked me, “Doesn’t silver oxidize?” That simple question prompted me to consider using gold instead, which eventually led to a new line of research on gold-based stretchable conductors.
Other times, people suggest specific use cases during outreach sessions or public demos—things they’d like to try in a playful way. Some of those spontaneous ideas have actually evolved into serious, exciting research topics. The “e-cosmetics” project I mentioned earlier is one such example that was inspired during outreach activities.
Toward a Future Where the Boundary Between Humans and Electronics Disappears
— Through your research, what kind of future society are you hoping to create?
I hope to eliminate the boundary between humans and electronics. If we can make electronic devices soft and transparent, they could one day integrate with the human body. Imagine a thin film on the skin that could subtly move muscles, monitor health data, or even change facial expressions—essentially turning the human body into a kind of “lightweight cyborg.”
Today, using a smartphone or computer often means stopping what you’re doing and entering a kind of “digital mode.” We’re bound to these devices in terms of time, attention, and physical interaction. But if our research progresses, I believe we’ll move toward a society where information is seamlessly embedded into daily life—where we can stay connected to data while still looking outward at the world around us. I want to keep exploring how electronics can support our lives in a way that feels natural and effortless.
— Finally, could you share your outlook for the future of your research?
It’s been more than ten years since I began this research in 2012. Back then, the concept of “stretchable conductive materials” was itself a brand-new topic. Since then, a wide variety of such materials have been developed, and I feel that we now have a fairly robust portfolio to work with.
Today, the focus has shifted. Rather than just developing new materials, we’re now entering a phase where the challenge lies in integrating these materials into more complex systems—creating devices that are not only sophisticated but also genuinely usable in real-world settings.
Looking ahead, I hope to collaborate with researchers in the field of Human-Computer Interaction (HCI), who study how people interact with computers to enhance user experience. I’m interested in developing components that could be used in entirely new types of devices emerging from that kind of research.
Above all, I want to stay true to my own curiosity. By working with industry partners and developing technologies that people can genuinely relate to and accept, I hope to contribute to a future where humans and electronics blend together in a seamless and natural way.
Profile
Naoji Matsuhisa
Associate Professor, Research Center for Advanced Science and Technology (RCAST), The University of Tokyo.
Naoji Matsuhisa received his B.S. in Electrical and Electronic Engineering from the University of Tokyo in 2012. He then pursued his graduate studies under Professor Takao Someya at the same university, earning his Ph.D. in Engineering in 2017.
Following his doctoral studies, he conducted postdoctoral research at Nanyang Technological University in Singapore and Stanford University in the United States. In 2020, he was appointed as a full-time lecturer at Keio University, while also serving as a PRESTO researcher for the Japan Science and Technology Agency (JST).
In 2022, he joined the Institute of Industrial Science at the University of Tokyo as an associate professor and assumed his current position at RCAST in 2023.
His research focuses on the development of next-generation wearable technologies through the use of soft nanoelectronic materials for interactive devices. He also contributes to the advancement of the field as the chair of the Flexible & Stretchable Electronics Research Group.
（Interview & Text: Teruko Ichioka / Photo: Kayo Sekiguchi）
