Scanning Electrochemical Microscopy as a Novel Proximity Sensor for Atraumatic Cochlear Implant Insertion

Abstract

A growing number of minimally invasive surgical and diagnostic procedures require the insertion of an optical, mechanical, or electronic device in narrow spaces inside a human body. In such procedures, precise motion control is essential to avoid damage to the patient’s tissues and/or the device itself. A typical example is the insertion of a cochlear implant which should ideally be done with minimum physical contact between the moving device and the cochlear canal walls or the basilar membrane. Because optical monitoring is not possible, alternative techniques for sub millimeter-scale distance control can be very useful for such procedures. The first requirement for distance control is distance sensing. We developed a novel approach to distance sensing based on the principles of scanning electrochemical microscopy (SECM). The SECM signal, i.e., the diffusion current to a microelectrode, is very sensitive to the distance between the probe surface and any electrically insulating object present in its proximity. With several amperometric microprobes fabricated on the surface of an insertable device, one can monitor the distances between different parts of the moving implant and the surrounding tissues. Unlike typical SECM experiments, in which a disk-shaped tip approaches a relatively smooth sample, complex geometries of the mobile device and its surroundings make distance sensing challenging. Additional issues include the possibility of electrode surface contamination in biological fluids and the requirement for a biologically compatible redox mediator.

Glucose and Lactate Miniaturized Biosensors for SECM-Based High-Spatial Resolution Analysis: A Comparative Study

“…Enzyme-based biosensors represent an important class of electrochemical probes suitable for single cell investigation by SECM. The optimization of the routes for the immobilization and miniaturization has largely been discussed ,, and applied to the detection of species with high spatial resolution in femtoliter volumes, e.g., for local detection in microenvironments or for the development of multisensor arrays, or implantable or portable devices . While the miniaturization brings some technical advantages such as steady state signals, fast response, reduced iR -drop, and an improved signal-to-noise ratio, , the reduced amount of immobilized biological recognition elements may lead to a limited sensitivity and loss of long-term stability, and requires further optimization of the biomolecule immobilization strategies. , Enzyme-based biosensors can be coupled with microfluidic systems to reduce the analyte volume (down to nanoliter) and to increase the sensitivity of the detection.…”

A dual wedge microneedle for sampling of perilymph solution via round window membrane

“…Another consideration is it is ideal to have a safety mechanism to prevent the contact of the needle tip to the inner ear structure such as the basilar membrane. This function can be complemented by a feedback system utilizing a proximity sensor (30). …”

Towards inferring positioning of straight cochlear‐implant electrode arrays during insertion using real‐time impedance sensing

“…For example, imaging feedback tools for analysis of CI placement include postoperative CT, 6 preoperative Magnetic Resonance Imaging to determine candidacy, 7 and real‐time fluoroscopy during surgery, 8 but these techniques are burdened by cost, patient radiation exposure, and/or lack of true real‐time visualisation 9 . Custom EAs have also been designed that incorporate strain gauges, 10 scanning electrochemical microscopy, 11 a fibre‐optic imaging probe, 12 or an electromagnetic sensor 13 for position sensing. Polymer optical fibre Bragg gratings have also recently been integrated into an experimental EA to detect forces and insertion trajectories 14 .…”