Joint research team from Pohang University of Science and Technology (POSTECH) develop a sensor that provides immediate visual indicator when harmful gases are detected.
Gas accidents such as toxic gas leakage in factories, carbon monoxide leakage of boilers, or toxic gas suffocation during manhole cleaning continue to claim lives and cause injuries. Developing a sensor that can quickly detect toxic gases or biochemicals is still an important issue in public health, environmental monitoring, and military sectors. Recently, a research team at POSTECH has developed an inexpensive, ultra-compact wearable hologram sensor that immediately notifies the user of volatile gas detection.
The team led by Professor Rho Junsuk of departments of mechanical and chemical engineering and Dr Kim Inki of Department of Mechanical Engineering with Professor Kim Young-Ki and Ph.D. candidate Kim Won-Sik of Department of Chemical Engineering at POSTECH has integrated meta-surface with gas-reactive liquid crystal optical modulator to develop a sensor that provides an immediate visual holographic alarm when harmful gases are detected. The findings from this study were published in Science Advances>.
Exposure to hazardous gases can be life-threatening especially for those working in such environments. Conventional gas detection devices are not widely used due to the high cost and complexity in production. Additionally, commercial gas sensors are difficult to use and have poor portability and reaction speed.
To solve these issues, the research team utilized the metasurface, well known as a future optical device known to have the invisible cloak effect through making visible objects disappear by controlling the refractive index of light. Metasurface is especially used to transmit two-way holograms or 3D video images by freely controlling light.
When exposed to gas, the meta-surface forms a holographic image alarm by using the polarization control of transmitted light that can change due to the orientation of liquid crystal molecules in the liquid crystal layer inside the sensor device. Moreover, 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 leukaemia.
The wearable gas sensor can detect even the most minute amount of gas of about 200ppm. the research team developed a one-step nanocomposite printing method to produce this flexible and wearable gas sensor. The metasurface structure, which was previously processed on a hard substrate, was 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. It is anticipated to be integrable with glass-type AR display systems under development at Apple, Samsung, Google, and Facebook.
Going a step further, the research team is 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. If these studies are successful, they 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,” said Professor Rho. “It is anticipated to be especially effective in more extreme work environments where acoustic and visual noise are intense.” [APBN]