Bio-Inspired Wearable Fabric Sensor Takes Notes from Octopus Suckers

Researchers from a Korean university have studied octopus to learn how to make better stick-on wearable sensors.

Nature is a powerhouse for influencing innovation. Recently, emerging wearable fabric sensors are inspired by the qualities of a sea creature with eight limbs—the octopus. 

A hybrid team of smart textile, nanotechnology, chemical engineers, and medical device experts in South Korea collaborated to develop a sticker-like nanofabric that mimics the special micro-sucking capability of the octopus (Chun et al, 2019).

The goal of this advanced material development was to create a flexible sensor that can stick onto the soft, uneven texture of the human skin, whether it is dry or wet.

Conductive Stickers

How did they do it? 

They patterned the sticker-like, O-shaped rings onto a mixed polyester fabric using wet chemistry methods. The rings were made of reduced graphene oxide nanoparticles as a high-performing, yet simple option. 

This nanomaterial is a great conductor of electricity and can contribute to the mechanical strength of the overall material. The polyester fabric introduced lightweight and flexibility features, kind of like a band-aid!

 

Image from the Bio-inspired Materials and Interfaces Lab (BMIL) at Sungkyunkwan University, Korea

 

The octopus’s suction cups naturally stick to all types of surfaces because of the fine hair and micro-rough features that enable their high holding power (Tramacere et al, 2014). Reduced graphene oxide has great adhesion properties following similar attention to fine features. 

Graphene-oxide has suction stress because of pulling forces between the two surfaces. In dry conditions, the main forces acting from the reduced graphene oxides are van der Waal’s forces; in wet conditions, it is capillary forces that help with suction (Baik et al, 2017).

Flexible Sensor Applications (Including Speech Recognition?)

Monitoring various human activities is the ultimate goal for material performance. On a commercial end, the flexible sensor can potentially collect data while an athlete is running or swimming, provide real-time data to medical professionals on a patient, and possibly enable a new speech recognition technology.

According to the journal article, the researchers collected raw data taking measurements from a 35-year-old person. The wrist pulse, dynamic body motions, electrocardiography (ECG), and speech vibration results show viability and proof-of-concept.

The overall results indicate responsiveness to applied strain as well as good sticking of the material onto the human skin. On the wrist, the fabric sensor detected bending motions while dry and wet, as well as 68 pulse beats over a 5 second period. Sensors were stuck onto the person’s wrists and ankle for ECG monitoring showing repeatable electrode output for potential medical diagnosis. 

 

A previous iteration of the team's research yielded other conductive and stretchable adhesive electronics. Image from the Bio-inspired Materials and Interfaces Lab (BMIL) at Sungkyunkwan University, Korea

 

On the neck, the fabric sensor picked up on vocal vibrations consistently with results output in the form of resistance change rates.

Wearable sensor end-uses can be possible with continual refinement of the advanced material and growing acceptance of nanomaterials from a consumer and legislative perspective. This wearable sensor innovation aligns well with market growth trends into 2025 anticipated throughout Asia and North America regions. This innovation also aligns with the demand of flexible wearable electronics sought after by tech companies like Apple and Samsung.

The wearable sensor field is at an evolving stage, inviting all sorts of experimentation and inspiration from nature. The ultimate goal is a high performing product to seamlessly blend into our everyday lives.

Sources

• Sungwoo Chun, Wonkyeong Son, Da Wan Kim, Jihyun Lee, Hyeongho Min, Hachul Jung, Dahye Kwon, A-Hee Kim, Young-Jin Kim, Sang Kyoo Lim, Changhyun Pang, Changsoon Choi. Water-Resistant and Skin-Adhesive Wearable Electronics Using Graphene Fabric Sensor with Octopus-Inspired Microsuckers. ACS Applied Materials & Interfaces, 2019; 11 (18): 16951 DOI: 10.1021/acsami.9b04206
• Tramacere, F.; Appel, E.; Mazzolai, B.; Gorb, S. N. Beilstein J. Nanotechnol. 2014, 5, 561–565. doi:10.3762/bjnano.5.66
• Baik, S.; Kim, D. W.; Park, Y.; Lee, T.-J.; Bhang, S. H.; Pang, C. A Wet-Tolerant Adhesive Patch Inspired by Protuberances in Suction Cups of Octopi. Nature 2017, 546, 396−400.