Research Team Discover Wearable Sensors That Detect Gas Leaks

Gas accidents such as toxic gas leakage in factories, carbon monoxide leakage of boilers, or toxic gas suffocation during manhole cleaning is something that is so dangerous, it has claimed lots of lives, with millions of dollars lost in injuries and destruction of properties. That’s why a group of researchers at POSTECH decided to tap into the opportunity and develop a sensor that can detect toxic gases.

The research team developed a wearable hologram sensor that is inexpensive and trendy and would notify the wearer of a gas leak.

The research team made up of Professor Junsuk Rho of the departments of mechanical and chemical engineering and Dr. Inki Kim of Department of Mechanical Engineering with Professor Young-Ki Kim and Ph.D. candidate Won-Sik Kim of Department of Chemical Engineering at POSTECH integrated the metasurface with gas reactive crystal optical modulator, developing a sensor that would provide an immediate visual holographic alarm when harmful gases are detected.

This is especially important and life saving for workers in hazardous environments such as petrochemical plants, who do not have access to conventional gas detecting devices due to their high cost and limitations -difficult to use, poor portability and slow reaction speed. Problems which were resolved by the research team with metasurface, well known as a future optical device known to have the invisible cloak effect, making visible objects disappear by controlling the refractive index of light. Metasurface is especially used to transmit two-way holograms or 3-D video images by freely controlling light. They then developed a gas sensor that can float a holographic image alarm in space in just a few seconds by using the polarization control of transmitted light that transforms due to the change in orientation of liquid crystal molecules in the liquid crystal layer inside the sensor device when exposed to gas. It is remarkable that this gas sensor developed by the research team requires no support from external mechanical or electronic devices, unlike other conventional commercial gas sensors. The researchers used isopropyl alcohol as the target hazardous gas, known as a toxic substance that can cause stomach pain, headache, dizziness, and even leukemia.

The newly developed sensor was confirmed to detect even trace amount of gas of about 200ppm. In an actual experiment using a board marker, a volatile gas source in our daily life, a visual holographic alarm popped up instantaneously the moment the marker was brought to the sensor.

The research team produced this flexible and wearable gas sensor using a one-step nanocomposite printing method. The metasurface structure, which was processed on a hard substrate, was then designed to enable rapid production with a single-step nanocasting process on a curved or flexible substrate.

When the flexible sensor fabricated using this method attaches like a sticker on safety glasses, it can detect gas and display a hologram alarm. There’s belief it will be integrable with glass-type AR display systems under development at Apple, Samsung, Google, and Facebook.

The research team is also developing a high-performance environmental sensor that can display the type and concentration level of gases or biochemicals in the surroundings with a holographic alarm, and is studying optical design techniques that can encode various holographic images. These studies if successful, can be used to reduce accidents caused by biochemical or gas leaks.

“This newly developed ultra-compact wearable gas sensor provides a more intuitive holographic visual alarm than the conventional auditory or simple light alarms,” remarked Prof. Junsuk Rho. “It is anticipated to be especially effective in more extreme work environments where acoustic and visual noise are intense.”