Printing Sensors Directly onto the Skin

Humans always develop and advance themselves of their capabilities. We are explorers. We explore every possibility that exists to improve ourselves and achieve our maximum. Technology helps us to do the same. Advancements in technology never end. Discovering a new technology opens the doors for more technologies. 

Every one of us is health-conscious we monitor ourselves each day to make sure we are living a healthy life. For this purpose, we built certain sensors that do the job for us. Sensors that monitor our body’s inner activities and feed them directly to our phones exist. These are ‘wearable sensors‘ which we wear on our bodies. 

But a recent breakthrough is making wearable sensors look like science fiction movies.

Wearable Sensors

Credit: MIT
Credit: MIT

Wearable Sensors are certain types of sensors we wear on our bodies. They have many applications. One of those use cases is health monitoring. Wearable sensors actively monitor or health statistics and feed the data to our phones or directly to the doctors. This technology is very handy as it makes us aware of health issues very early so we can take adequate medical care. 

Wearable sensors are available in different shapes and form factors. Some come as smartwatches like the Apple Watch 6, which comes with a built-in blood-oxygen sensor. This lets the user measure the blood-oxygen levels in the body. Such technologies are very beneficial for people with health concerns or ones who are undergoing medical treatment.

There are other sensors that go inside the body which can measure internal activities. The proposed Neuralink device by Elon Musk can detect and monitor brain activity. It can also monitor the overall health of the user and report it onto their phones.  

Sensor Printed directly on the skin
Credit: Ling Zhang, Penn State/Cheng Lab and Harbin Institute of Technology
Sensor Printed directly on the skin Credit: Ling Zhang, Penn State/Cheng Lab and Harbin Institute of Technology

Such devices are very useful in monitoring one’s health and activities. 

A recent breakthrough in this wearable technology is making news as it looks like something out of a science fiction movie. 

Printing Wearable Sensors onto the Skin

An international group of researches just set the next level of wearable sensors by printing them directly onto the skin. They also did this without the application of heat. Impressive!

Huanyu "Larry" Cheng
Credit: Penn State College of Engineering
Huanyu “Larry” Cheng Credit: Penn State College of Engineering

Huanyu “Larry” Cheng is the Dorothy Quiggle Career Development Professor in the Penn State Department of Engineering Science and Mechanics. He and his research team broke new ground in making a method to print circuits onto the skin without heat. They published their innovations in the ACS Applied Materials and Interfaces. 

“In this article, we report a simple yet universally applicable fabrication technique with the use of a novel sintering aid layer to enable direct printing for on-body “- Ling Zhang, Harbin Institute of Technology in China and Cheng’s laboratory.

Cheng previously developed printed circuits on flexible boards used as wearable sensors, but printing directly on the skin was a challenge. The major problem is the heat. The bonding process, called Sintering, for the metallic compounds of the sensor, requires temperatures of up to 300 degrees celsius. Such high temperatures are harmful to the skin.

To solve this problem, Cheng added a nanoparticle layer called a sintering aid layer. This layer protects the skin while allowing the bonding process to carry on at around 100 degrees. Since 100 degrees is still not safe for the skin, they changed the formula of the aid layer and also changed the materials. This helped them achieve sintering at room temperatures. 


The sensor can precisely capture temperature, humidity. Heart rates and blood oxygen levels. It links to a wireless transmission network to monitor the activity in real-time. 

The sensor is also environmentally friendly. It is washed off easily with boiling water while it will stay robust on tepid water. The washed off circuit will remain intact and can be recycled. The removal will also not damage the skin in case of people having sensitive skin. 

Future Development

The team is now aiming to develop the technology to work on specific applications. The user can request the use case and the specific data the sensor needs to detect. They can also use it as an on-body sensor network that can monitor particular symptoms of COVID-19.

Wearable sensors like this will profoundly aid the medical industry in monitoring the health of patients. The current situation of the world needs such innovations to monitor and isolate people that show COVID-19 symptoms. These will also come in handy in case of similar situations.

Read more on Engineers’ print wearable sensors directly on skin without heat.

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