Researchers from the Federal University of Pernambuco (UFPE) have developed a cotton thread bathed in graphene that uses egg whites to increase efficiency and reduce costs in the production of electricity-conducting threads, essential for the development of electronic clothing.
The hive-like geometry of the graphene molecule provides strong cohesion between its carbon atoms, thereby enabling its structuring in a single layer to produce a fine, light, strong material with excellent thermal and electrical conductivity (see Pesquisa FAPESP issue nº 291). Associating this to cotton threads would be an efficient alternative for the production of textile threads with electrical conductivity; the threads could be used in flexible sensors and electronic clothes, in turn used for thermal control, monitoring of vital signs, or internet access.
Graphene, however, does not easily adhere to cotton, requiring 80 repetitions of the process of steeping the threads in graphene oxide — a liquid — and drying, to obtain the desired result. The process is time-consuming and expensive, motivating the UFPE team, coordinated by chemist Patrícia Araújo, to seek alternatives.
Polydopamine, a self-adhesive polymer, and polyvinyl, a synthetic, water-soluble polymer, were tested with a degree of success by the group, and reduced the number of immersions required to cover the cotton with graphene by 10. Bovine serum albumin, a protein from cow’s blood, presented better results with just one soak, but its extraction is difficult and expensive.
The researchers tested the egg white as a more accessible source of protein at lower cost. Treatment of the threads with albumin from the egg reduced the immersion requirement to 5 times, obtaining an ideal electrical resistance of 80 Ωg/cm² (ohm, represented by the Greek letter omega, the unit of measure for electrical resistance, multiplied by gram, then divided by square centimeter). This value remained the same after the threads underwent 104 flexion tests, during which they are folded, and 5 washing tests to evaluate the adhesion of the coating, as outlined in an article published in March in the journal Materials Research.
“Even with a greater requirement for immersion than with bovine serum albumin, the advantage of egg whites is considerable,” says Araújo. “Bovine albumin is 40 to 50 times more expensive.” The researchers are seeking out partnerships with corporations to ramp up the production scale of the conducting threads.
The team from the Federal University of Vale do São Francisco (UNIVASF), Juazeiro campus, in Bahia State, found another way to make the cotton threads capable of producing and storing energy: coating them with a double layer of carbon and graphene nanotubes, and then covering them with a plastic polymer (see Pesquisa FAPESP issue nº 331). The process was described in an article published in April 2018 in the journal ACS Applied Materials & Interfaces. It is a more complex and expensive technique than that proposed by the UFPE researchers.
Scientific articles
DINIZ, F. et al. Graphene-based flexible and eco-friendly wearable electronics and humidity sensors. Materials Research. vol. 27, e20230480. mar. 12, 2024.
LIMA, M. A. P. et al. Multifunctional wearable electronic textiles using cotton fibers with polypyrrole and carbon nanotubes. ACS Applied Materials & Interfaces. vol. 10, no. 16. apr. 2018.
