An alcoholic drink will give you a buzz, but if someone laced it with something dangerous, a new poison-snooping patch will buzz your skin to warn you. It can also detect heavy metals in water and toxic aerosols, and can work as an e-skin for robots.
Erim Uzunoğlu, first author of a Device paper and a PhD student at North Carolina State University, explains that his team was trying to create a real-life version of a poison-snooper from Dune, or a wearable version of a Finnish device for detecting invisible but dangerous amounts of cyanobacteria.
“We wanted to miniaturize sensors and incorporate them into a wearable patch to identify any potential risks to the wearer,” says Uzunoğlu, referring to existing devices that can already “detect environmental hazards and send notifications to your phone.” Those risks include heavy metals in water, dangerous gases, and toxic aerosols.
Following detection, the NCSU patch – about the size of a business card – alerts its wearer simply by vibrating against the skin. But why not simply send an alert to a cellular telephone?
“If you’re coming into contact with a hazardous substance, you need to know as quickly as possible,” explains Uzunoğlu. “If the notification is being sent to your phone, you may not check it right away. So, we wanted to incorporate haptic technology into the patch so that it would vibrate as soon as the hazard was detected, allowing people to respond quickly to the potential threat.”
To ensure the haptic signal is sufficiently alarming, the team did more that relying on a vibrational buzz, and instead created a type of poison-warning Braille that identified which danger was present.
“We designed tiny textured surfaces that sit at the interface between the motor and your skin, almost like a miniature pattern of bumps,” says co-author Oluwatobi Ojuade, who is also an NCSU PhD student. “By changing the size and spacing of those bumps, we could control how the vibration is perceived against your skin. That let us fine-tune the sensation so it actually grabs your attention, instead of feeling like a faint buzz you might miss.”
Containing its own battery, sensors for six environmental hazards, a microcontroller, and an actuator that provides vibration, the patch exists inside its own “skin” of photovoltaic cells, leveraging its location on the skin to recharge from sunlight. Rather than being a delightful add-on, rechargeability in a poison-snooper could save lives in non-electrified remote locations, or in disaster zones where electricity is temporarily unavailable.
“We also found the energy harvesting technology did a good job of extending the life of the battery,” says Uzunoğlu. “Coupled with the low power demand of the sensors, this allows the device to function for around 24 hours.”
Of course, for the sensors to send danger signals, they need to come in contact with potentially lethal chemicals in the water or air. So, while users might be safe inside their homes or vehicles, taking a few steps outside to wait for the sensors to register danger might be a potentially lethal sojourn. Wouldn’t it be better if your robot butler could check outside for you and call out, “The water’s fine!” or “We seem to be made to suffer. It's our lot in life”?
That’s why the team developed a robotic “e-skin” of piezoelectric material that creates an electrical signal that alerts the robot whenever the actuator vibrates, allowing the robot to detect the danger.
“The patch and e-skin are largely made using off-the-shelf components, with very few custom-engineered elements,” says co-corresponding author Amay Bandodkar, who is also an NCSU assistant professor of electrical and computer engineering. “That should make it easier to scale up the technology moving forward. And the concept is extremely flexible – the sensor array is modular, so you can add or remove sensors that monitor for whichever hazards are most relevant to the application.”
For Lilian Hsiao, co-corresponding author and NCSU associate professor of chemical and biomolecular engineering, her team’s breakthrough is more than welcome. “It’s quite amazing to see that we can encode tactile signals into materials of different properties, something that has been very challenging to do in the past – especially in real-world situations where people would want to wear the device. To combine something that people would wear, along with sophisticated sensing capabilities and the ability to alert the user, is something we’ve been working on for a long time.”
Source: North Carolina State University
