VCU research propels wearable technology that could enhance health monitoring

By Anastasia Mineiro

In a potential advance for wearable technology, researchers from Virginia Commonwealth University and Florida International University have developed a cold-spray technique that can reliably deposit sensors directly onto human skin and other flexible surfaces.

Wearable sensors offer substantial benefits for health monitoring, human-machine interaction and flexible electronics, yet fabrication often relies on costly, multistep processes with limited scalability. The researchers report that their technique provides strong adhesion of sensors to flexible surfaces while maintaining mechanical robustness and the potential for scalable manufacturing.

The expansion of wearable technology has led to a growing need for low-cost, expandable and high-performing sensors, said Arvind Agarwal, Ph.D., chair and professor in the Department of Mechanical and Nuclear Engineering in VCU's College of Engineering. These sensors allow for continuous health monitoring and customized health care for the individual wearing them.

Agarwal and the research team created an improved wearable pressure sensor and a first-ever cold-spray method to adhere it to the human body. The sensor is made of polydimethylsiloxane polymer, a soft, stretchy rubber material that molds to where it is applied. The cold spray directly applies graphene nanoplatelets to the PDMS material for durable adhesion onto human skin.

"The sensor can be made by spraying the sensing material [graphene] directly onto a flexible surface, without glue or several complicated steps," Agarwal said. "That could make it easier to produce wearable devices that help track signals from the body."

Traditional adhesion methods for sensors require heating or adding chemicals and binders. The cold-spray method allows for dry, room-temperature adhesion that does not tamper with the other materials in the sensor when applied.

The study, "Cold-Spray Enabled Scalable Manufacturing of Flexible Graphene-Based Wearable Sensors," was published in ACS Publications and co-authored by Florida International University researchers Azmal Huda Chowdhury, Denny John, Anil Lama and Rony Thomas Murickan. Their research was conducted through a series of experiments and was tested on one human subject.

Key findings of the study include:

• The sensor quickly reacted, at 29 milliseconds, for a press-and-release response.
• It continued to work after more than 5,000 presses.
• It was able to pick up a person's wrist pulse.

"The work was possible when researchers from two very different expertise work together," Agarwal said, praising his materials-science colleagues. "Hence, teamwork and collaboration are critical to travel the path which has not been explored."