Electrodes printed on flexible substrate can be applied to skin

electrodes
An array consisting of gold nanoparticles is inkjet printed on plastic and can be used to measure various biological processes associated with variations in electrical potential (photo: archive of Felippe José Pavinatto)

Brazilian researchers have contributed to the development of a new technique that enables an array of electrodes consisting of gold nanoparticles to be inkjet printed on flexible plastic. An article describing the technique, “Inkjet-Printed Flexible Gold Electrode Arrays for Bioelectronic Interfaces”, was featured on the cover of a recent issue of the journal Advanced Functional Materials.

The material, which can be used as a biosensor, among other applications, was developed at the University of California, Berkeley, in the United States and the University of São Paulo (USP) in Brazil by an international collaboration including two Brazilian researchersFelippe José Pavinatto and Ana Claudia Arias.

Pavinatto, who is affiliated with USP’s São Carlos Physics Institute (IFSC-USP), was supported by a scholarship for research abroad from FAPESP.

“Flexible gold electrodes are ideal for devices that measure bioimpedance and biopotential by means of tomography, electrocardiography, electroencephalography and electromyography,” Pavinatto told Agência FAPESP.

The chief advantages of these electrodes are that they are flexible and chemically inert. Their flexibility ensures optimal contact with skin and tissue, whereas their chemical inertness prevents the electrodes from reacting with biological fluids and living cells. “We could even consider the possibility of printing the electrodes on adhesive tape, like the sticking plaster used in dressings,” Pavinatto said.

The fabrication process is very similar to conventional inkjet printing. The key difference is that the cartridge is filled with gold nanoparticles instead of ink. “Sintering occurs at a relatively low temperature, on the order of 200 degrees Celsius, and the sintering speed depends on the width of each line in the electrode,” Pavinatto said. “The technique permits tight control of the process and significant versatility to modify the layout during execution if necessary.”

The electrodes are sensitive enough to detect differences in potential as small as a few millivolts. In addition to the applications mentioned, they can be used to measure any biological process associated with variations in potential, such as heart rate, blood sugar levels, or cell damage that is likely to lead to future skin ulcerations (in bedridden patients, for example), among others.

“Because the gold nanoparticles and plastic substrate are biocompatible, in principle, the electrodes can not only be used on the skin but also implanted inside the body. This possibility is being evaluated,” Pavinatto said.

Previous articles by Pavinatto and collaborators described similar electrodes designed to detect antioxidants in “Printed and flexible biosensor for antioxidants using interdigitated ink-jetted electrodes and gravure-deposited active layer” and skin ulcerations in “Impedance sensing device enables early detection of pressure ulcers in vivo”. A note on the latter was published by the magazine Pesquisa FAPESP.