Researchers from a Korean university have studied the octopus to learn how to make wearable sensors stick better.
Nature is a powerhouse to influence innovation. Recently, emerging wearable tissue sensors are inspired by the qualities of a sea creature with eight limbs: the octopus.
A hybrid team of smart textiles, nanotechnology, chemical engineers and medical device experts in South Korea collaborated to develop a sticker-shaped nanofabric that mimics the octopus’s special micro-suction ability (Chun et al, 2019).
The goal of this advanced material development was to create a flexible sensor that adheres to the smooth and uneven texture of human skin, whether wet or dry.
How they did it?
They modeled the sticker O-rings on a polyester blend fabric using wet chemistry methods. The rings were made of reduced graphene oxide nanoparticles as a simple, high-performance option.
This nanomaterial is a great conductor of electricity and can contribute to the mechanical strength of the material in general. Polyester fabric introduced lightweight and flexible features, like a band-aid!
Image from Bioinspired Materials and Interfaces Laboratory (BMIL) at Sungkyunkwan University, Korea
Octopus suction cups adhere naturally to all types of surfaces due to the characteristics of fine and micro-rough hair that allow their high holding power (Tramacere et al, 2014). Reduced graphene oxide has great adhesion properties after similar attention to fine characteristics.
Graphene oxide has a suction stress due to the tensile forces between the two surfaces. In dry conditions, the main forces acting on reduced graphene oxides are the van der Waal forces; in humid conditions, it is capillary forces that help with suction (Baik et al, 2017).
Flexible sensor applications (includes voice recognition?)
Monitoring various human activities is the ultimate goal for material performance. In a commercial aspect, the flexible sensor can potentially collect data while an athlete is running or swimming, it can provide real-time data to a patient’s medical professionals, and possibly enable new speech recognition technology.
According to the journal article, the researchers collected raw data from a 35-year-old. Wrist pulse, dynamic body movements, electrocardiography (ECG), and speech vibration results show feasibility and proof of concept.
The overall results indicate the responsiveness to applied stress, as well as good adhesion of the material to human skin. On the wrist, the fabric sensor detected bending movements while dry and wet, as well as 68 pulsations over a 5-second period. The sensors were glued to the person’s wrists and ankle for ECG monitoring, showing repeatable electrode output for possible medical diagnosis.
An earlier iteration of the team’s research produced other conductive and stretchable adhesive electronics. Image from Bioinspired Materials and Interfaces Laboratory (BMIL) at Sungkyunkwan University, Korea
In the neck, the tissue sensor captured the vocal vibrations consistent with the results obtained in the form of rates of resistance change.
End-uses for wearable sensors may be possible with the continued refinement of advanced material and the increasing acceptance of nanomaterials from a legislative and consumer perspective. This wearable sensor innovation aligns well with anticipated 2025 market growth trends across all Asian and North American regions. This innovation also aligns with the demand for flexible electronic devices sought after by technology companies such as Apple and Samsung.
The field of the portable sensor is in a stage of evolution, inviting all kinds of experimentation and inspiration from nature. The end goal is a high-performance product to blend seamlessly into our everyday lives.
- Sungwoo Chun, son of Wonkyeong, Da Wan Kim, Jihyun Lee, Hyeongho Min, Hachul Jung, Dahye Kwon, A-Hee Kim, Young-Jin Kim, Sang Kyoo Lim, Changhyun Pang, Changsoon Choi. Waterproof and skin-adhesive portable electronics utilizing a graphene cloth 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, SN Beilstein J. Nanotechnol. 2014, 5, 561–565. doi: 10.3762 / bjnano.5.66
- Baik, S .; Kim, D. W .; Park, and.; Lee, T.-J .; Bhang, SH .; Pang, C. A moisture tolerant adhesive patch inspired by the bumps on octopus suction cups. Nature 2017, 546, 396−400.