Biosensors Printed Directly on Skin Bring Wearable Tech to Next Level

Wearable biosensors have been around for some time, in one form or another. However, new technology allows you to print the biosensor directly on the skin without the need for other devices or to handle sticky tape. This could have a tremendous impact on the world of medical care.

Why Wearable Biosensors Are Necessary

The skin is the biggest organ in the body, and it can give doctors quite a bit of information when monitored. Everything from skin tone and color changes to temperature and adaptations such as lesions or various rashes can tell a doctor what is happening inside the body. However, many other symptoms show up in the skin or the sweat and oil produced there, which cannot be checked by vision or touch. This is where biosensors become useful.

Nurses can take a patient’s temperature from time to time and mark it, but how much more useful is it to continuously monitor its temperature and see exactly when it rises or falls? The same goes for heart rate and other vital signs, all of which can be checked by a doctor even if they are nowhere near their patient at the time. In fact, some wearable sensors are set to alert the doctor and the patient of an abnormality or issue that may need medical attention.

However, until now, there were a few issues with biosensors being worn.

The History of Wearable Sensors

Most people are familiar with Fitbit and other types of smartwatches which allow you to monitor a range of vital signs while you move around. They include sensors on the bracelet and measure everything from heart rate to steps and sleep habits. While useful, these were meant more for individual use rather than medical. Over time, however, smartwatches and other bracelets became more useful with the addition of apps like the Apple Heart Study app, which alerts you if you have atrial fibrillation.

Smart clothing was developed with nano-sensors included in the actual fabric and tracked all body types. Diabetic socks monitor feet and alert the wearer’s doctor if foot temperature rises, indicating inflammation. Since inflammation may indicate infection or injury, this is very helpful in preventing amputations in people with diabetes who may not feel damage to their feet.

Originally, skin-based biosensors were more invasive and have been used for things like glucose monitoring. These used microneedles that could be solid or hollow to sample the interstitial fluid. These needles permitted the device (usually a wearable skin patch with the needles on the underside) to continually monitor blood sugar, which could stimulate an attached insulin pump to provide more insulin when necessary.

The next step was to create a printed biosensor that could stick to the skin yet allow sweat to penetrate the membrane and reach the actual sensor part of the device. While non-invasive and easy to use, this type of biosensor still requires peeling and sticking to the skin and may catch or be ruined during application. They also tend to have some separation from the skin and could end up with incorrect assessments.

Other issues with the biosensor stickers include that it was difficult to get them off at times, and other times, they tend to come off on their own. The adhesive may also be irritating to the skin. It was high time for a brand new type of technology.

Printable Biosensors: Challenges and Risks

Printing onto a piece of paper or plastic is one thing, printing on the skin is another ball game. Since biosensors include metal components, the printing was previously impossible without causing burned skin, as the metal had to be heated to a high temperature before printing.

The newest technology, developed by the US and Chinese scientists led by Larry Cheng of Penn State University, is different. It lets doctors print directly onto the skin of ill patients without burning them, thanks to using polyvinyl alcohol or calcium carbonate on the skin first. Scientists could drastically lower the temperature by adding several nanoparticles to the paste, including copper, metallic salts, magnesium oxides, and aluminum.

The next step was to print the sensors with silver nanoparticles at room temperature on top of the specially prepared paste. Finally, cold air is blown over the area to eliminate any moisture. This helps the sensors bond to the skin for a longer-lasting image.

While still at a prototype stage, the tech would mainly detect when a cardiopulmonary patient requires further treatment. In fact, for Covid-19 patients, the biosensors would help doctors determine exactly when to apply treatments and catch the moment the patient begins to have issues.

The sensors are ideal for monitoring body temperature, hydration, blood oxygen saturation, and even ECG signals. In the future, it may be used by athletes or even workers in dangerous areas. Now that the team has determined how to print directly onto the skin, they can expand the sensor’s capabilities as needed for individual situations.

Why is it so important to have sensors printed right on the skin? That’s because applied biosensors may not be as accurate and can have gaps in contact. Printing directly ensures perfect contact and the highest possible accuracy.

To remove the sensor, hot water can wash it away easily without damaging the skin. However, it remains stable in cool water, so the user can swim or take cool showers without worry.

The ability to continuously monitor a patient means doctors can send more people home but still keep an eye on them. If anything triggers an alarm remotely, the doctor can dispatch help or ask the patient to come in for a visit.

Biosensors are definitely becoming more important in medicine today, and it’s reasonable to expect that they will soon become the norm for medical workers. However, they also have many other applications, so don’t be surprised if the next athletic boost is a printable biosensor.