Screen Time

Flexible, wearable electronics are becoming an increasingly popular trend in the tech industry, with devices such as smartwatches and fitness trackers being widely adopted by consumers. However, the manufacturing process for these devices is proving to be costly, complex, and error-prone.

One of the main challenges facing the manufacturing of flexible, wearable electronics is the high cost of materials. The materials used in these devices, such as flexible displays and sensors, are still relatively new and therefore expensive to produce in large quantities. This makes it difficult for manufacturers to produce devices that are both affordable and high-quality.

Another major challenge is the complexity of the manufacturing process. The process of creating flexible electronic devices involves many different steps, including the printing of thin film transistors, the creation of the flexible substrate, and the assembly of the final device. Each step must be done with a high level of precision and accuracy, which can be difficult to achieve and increases the risk of errors.

Contrast that process with screen printing, also known as silk screening, which is a printing technique that has been used for centuries. The process involves pushing ink through a stencil, or screen, onto a surface. The stencil is created by blocking off sections of a mesh screen with a non-permeable material, leaving only the desired design open to allow ink to pass through.

Not only is this process incredibly simple (it can even be done by hand), but it can also be performed with minimal, and very inexpensive, equipment. But this process is best known for its use in printing designs on t-shirts, so what is the connection with wearable electronics, you ask? Well, a team led by researchers at Washington State University was inspired by this technique, and set about experimenting with it to see if it could be modified to print flexible, wearable electronic components like electrodes.

The process involved printing multiple layers of a polyimide and polyethylene glycol mixture on a glass slide, interspersed with a patterned, conductive layer of silver. After the print process is complete, the screen printed material can be peeled off of the slide, and attached to fabric or the body. A serpentine pattern was used to create electrodes that proved to be highly deformable. They were shown to be able to stretch up to 30% larger than their normal size, and to be able to bend up to 180 degrees without damage.

The researchers put their new methods to the test in a real world experiment. They manufactured and tested a wearable device designed for real-time wireless electrocardiogram monitoring. The printed electrodes and flexible printed circuit, in conjunction with an algorithm that was developed to process the sensor data, was found to calculate accurate heart rates, respiratory rates, and heart rate variability metrics. The latter metric may have clinical applicability in arrhythmia detection.

An advantage to the team’s approach is that it can easily scale up — the same techniques that they are using to create single devices can be used to mass produce a commercial wearable. And that could come in handy. The underlying technology has many applications beyond medical devices, and could be used in smartwatches or fitness trackers in the future.