Stretchable Electrodes for Medical Devices

Abstract

[Key topics: ElectrodesElectrodeposition techniquesElectrochemical propertiesStructure – physical properties relationships] The fabrication of electrodes on polymers, and especially on elastomers, is relevant in several fields. Among them, the medical field can benefit a lot from these kinds of electrodes. The human body uses electrical signaling in the muscles as well as in the nervous system to transfer energy and information between the brain and the rest of the body. Cardiac pacemakers, neuromodulation systems, neuromonitoring systems, brain machine interfaces are all examples where electrodes play a key role. Most of the body tissues are soft with unique shapes. When it is required to transfer electrical signals between the soft tissues and hard electronic systems, having soft and conformable interfaces might be particularly advantageous to increase the efficacy of the therapies, the energy consumption of the medical devices and the patient’s quality of life.We have developed several solutions to obtain metal patterns on elastomers that are stretchable, strongly adhered and with high charge-storage capacity. The methods are based on SCBI (Supersonic Cluster Beam Implantation) that allows to form a nanocomposite made of metal nanoparticles embedded in the elastomer, which acts as seed where thin film electrodes are created either through physical vapor techniques or by electro or electroless deposition.Here we compare electrodes made of Pt, Pt-Ir, Ir and IrOx obtained via electrochemical and physical vapor techniques. We present how, by tuning the process parameters, is possible to control the electrodes properties such as the charge-storage capacity, the corrosion under electrical stimulation and stability to tensile and compressive stresses. We show how the electrochemical and mechanical properties are correlated to the micro-structure, the grain morphology, and the stoichiometry. It is also shown how obtaining the electrodes with the right specific surface area is essential to guarantee stability against corrosion under high currents input.