Carbon heterostructures based on carbon nanotubes and graphite formed by laser radiation

Classic electrode interfaces based on metallic compounds, such as Ag/AgCl, have a number of significant drawbacks: the need for an electrolytic gel layer and the risk of allergic reactions. The integration of carbon particles, such as carbon nanotubes, graphene, and graphite, into polymer matrices, such as polydimethylsiloxane (PDMS), will enable the creation of dry electrodes. These electrodes overcome the drawbacks of wet electrodes and enable long-term monitoring of biopotentials. The objectives of this work were laser formation and study of the electrical properties of composites based on electrically conductive carbon heterostructures of carbon particles in a PDMS matrix. The formed heterostructures were networks of covalently bonded multiwalled carbon nanotubes (MWCNT) and graphite particles under laser irradiation. Composite samples with different weight concentrations of carbon nanomaterials were formed. It was found that a composite based on an MWCNT/graphite composition with concentrations of3/5 wt.%, respectively, had the lowest resistance. Pulsed laser treatment (1064 nm, 100 ns, 30 kHz) made it possible to form carbon heterostructures in a polymer matrix with a given geometry. This led to a 5-fold decrease in resistance to 200 Ohm. The structural, electrical, and mechanical properties of the composites were studied. The structure of the samples was investigated using Raman spectroscopy. The obtained changes in the ID/IG ratio as a result of laser treatment confirm local rearrangements of the electronic structure of MWCNTs with the formation of new bonds. Mechanical properties studies showed that a composite based on PDMS/MWCNT/graphite heterostructures after laser irradiation withstood a load of 7.9 N and stretched to 9.4 mm before breaking. Thus, a method for laser-induced formation of electrically conductive carbon heterostructures in a PDMS matrix has been developed. The results confirm that the developed composites based on carbon heterostructures are suitable for continuous monitoring of physiological parameters of the human body.