Enhanced Flexible Tubular Microelectrode with Conducting Polymer for Multi-Functional Implantable Tissue-Machine Interface

Abstract

Implantable biomedical microdevices enable the restoration of body function and improvement of health condition. As the interface between artificial machines and natural tissue, various kinds of microelectrodes with high density and tiny size were developed to undertake precise and complex medical tasks through electrical stimulation and electrophysiological recording. However, if only the electrical interaction existed between electrodes and muscle or nerve tissue without nutrition factor delivery, it would eventually lead to a significant symptom of denervation-induced skeletal muscle atrophy. In this paper, we developed a novel flexible tubular microelectrode integrated with fluidic drug delivery channel for dynamic tissue implant. First, the whole microelectrode was made of biocompatible polymers, which could avoid the drawbacks of the stiff microelectrodes that are easy to be broken and damage tissue. Moreover, the microelectrode sites were circumferentially distributed on the surface of polymer microtube in three dimensions, which would be beneficial to the spatial selectivity. Finally, the in vivo results confirmed that our implantable tubular microelectrodes were suitable for dynamic electrophysiological recording and simultaneous fluidic drug delivery, and the electrode performance was further enhanced by the conducting polymer modification.

Poly(3,4-ethylenedioxythiophene) (PEDOT) Coatings for High-Quality Electromyography Recording

“…As discussed in the introduction, the two main mechanisms that allow PEDOT-coated electrodes to achieve a better signal quality are the reduced thermal noise and the reduced shunt loss. However, another interesting finding has been previously reported, which involves the reduction of the 50 Hz (or 60 Hz) noise which results from the electronic recording setup, but the authors did not provide an explanation of the phenomenon [56,90]. In this study, we observed the same phenomenon as the 60 Hz noise was constantly lower for PEDOT-coated electrodes.…”

“…The Cdl value was higher for films prepared in ACN respect to the other two solvents, which may result from the more porous nature of the film. At the same time, the Cd values were higher for films obtained in organic solvents compared to coating polymerized in water, which may suggest a thicker layer in the formers [90]. This would be confirmed also by the lower bounded Warburg element value obtained for coatings prepared in water, which in the literature has been associated…”

“…Still, other groups have also reported that the 50 Hz (or 60 Hz) noise, which normally affects all the signal measurements due to the electronic noise from all the electronic components in the recording room, is reduced by using PEDOT as an electrode coating [56,90]. This was also the case in this study (Figure 4.18) as the 60 Hz noise amplitude was consistently higher for uncoated electrodes (except for the last week during which in one of the animals the bare electrodes experienced an anomalous drop of the noise).…”

“…PEDOT coated electrodes showed enhanced signal amplitude and lower 50 Hz noise, which resulted in better single motor unit action potentials recording. The same group later improved this device using a single structure obtained by wrapping a Parylene C substrate containing the gold electrodes on a flexible polymer-based microtubular structure for parallel drug delivery[90]. PEDOT:PSS was then electropolymerized on the gold electrodes, which caused a dramatic reduction of the impedance over the whole frequency range (10 -1 -10 5 Hz) and an increase in CSC compared to bare gold.…”

Compliant peripheral nerve interfaces

“…The integration within a single system of multiple modalities (figure 7) to communicate with the PN is enabled by the introduction of precise fabrication techniques and miniaturisation. Concurrent electrophysiological recording from microelectrodes integrated with a drug delivery outlet allows for in situ verification of nerve blocking effects [195]. Selective stimulation and recording has been achieved by attracting axons to the electrodes thanks to the combined effect of lysing agents which remove connective tissue and neurotrophic factors to promote axonal growth [186,196].…”