Using a solution of graphene and carbon nanotubes coated on fabric as a sensor

A sensor has been developed that is waterproof and has high conductivity even when bent or pressed repeatedly.

The Electronics and Telecommunications Research Institute (ETRI) announced that it has succeeded in developing a fabric-type composite sensor capable of simultaneously measuring pressure and strain by immersing fabrics such as cotton fibers in a solution containing graphene and carbon nanotubes, then removing them and drying them.

The research team successfully created a motion sensor that detects movement according to finger movements by grafting the sensor they created onto a cotton glove.

Until now, sensors have primarily utilized conductive metals that conduct electricity well. However, metals have been difficult to bend and break easily with repeated bending, hindering their commercialization due to their poor flexibility and durability.

The research team developed a sensor that is thin yet strong, and chemically stable against sweat, chemicals, and other substances. It is also water-resistant, meaning it can be washed without any issues, and requires no additional functional modifications.

The key to this research and development achievement lies in the combination of reduced graphene and carbon nanotubes. This resulted in the realization of a fabric-type composite sensor capable of measuring pressure and strain. The sensor measures approximately 1 x 3 cm. It can be manufactured on a large area, up to several tens of centimeters, with no design or size restrictions. It can also be applied directly to fabric without any problems.

Since the material itself is a sensor, this technology is similar to coating fabric. It coats conductive graphene like a dye. Therefore, you can cut it as much as you want and use it as a sensor.

"Reduced graphene" is made by chemically reducing graphene oxide, which is made by oxidizing graphite, the material used in pencil lead. Because graphene oxide is an insulator, oxygen (O2) must be removed from the graphene oxide to make it conductive.

Graphene-based fabric sensors created through this process can be mass-produced and exhibit a variety of properties, including excellent electrical conductivity, hydrophobicity, excellent flexibility, and large-area applications. In this study, the process for manufacturing a high-quality reduced graphene solution was conducted by Dr. Ki-Seok Ahn's team at the Korea Research Institute of Chemical Technology.

Meanwhile, 'carbon nanotubes' have excellent thermal conductivity and mechanical and electrical properties, so they are used as additives in various structural materials.

The ETRI research team took advantage of the strengths of the two materials and increased electrical conductivity by grafting carbon nanotubes onto graphene-coated fabric. They also explained that the complex network structure of the carbon nanotubes ensured durability even after being bent or pressed more than 100,000 times.

The research team announced that they plan to apply the developed sensor to a wearable material, gloves, and distribute it to robot hands or patients who have difficulty using their hands or feet and wear prosthetic arms and legs.

Dr. Choi Chun-ki of the New Device Research Group at the ETRI ICT Components and Materials Research Institute said, “We also confirmed the superiority of the sensing performance, such as the composite sensor maintaining linearity as the measurement range changes and the measurement process being completed within a few seconds.”