Abstract
Abstract Over the years, a constant progress in the development of implantable medical devices (IMD’s) can be observed. On one hand, the advanced implantable electronics enable the implementation of numerous smart functionalities, on the other hand, the variety of electronic components including sensors and a bulky battery severely restrict their degree of miniaturization and reliability. To overcome this limitation, our approach is to realize smart functionalities in leadless and battery-free IMD’s emerging from frugal innovation by exploiting the intrinsic nonlinear properties of the components to be used anyway. The aim of this work is to deepen the understanding of the dynamic behavior of circuit topologies of nonlinear ferroelectric ceramic capacitors and to investigate their potential use for an embedded closed-loop control of the stimulation current. We characterized a selection of 40 commercial ceramic capacitors by measurement and simulation. The degree of nonlinearity resulting from a circuit topology consisting of one, two series and two parallel connected nonlinear capacitors was modeled and evaluated in Mathcad. We present a model with parameterized nonlinear capacitors to simulate the dynamic behavior of an inductively coupled implantable system. The stabilization and amplitude of the stimulation current is controlled by two features. These features are in turn controlled by the circuit topology and the degree of nonlinearity of the capacitors. We found that a high degree of nonlinearity allows the stimulation current to be stabilized within a reasonable range, but it makes the system more prone to instability. However, our model needs to include the dynamic behavior of ferroelectric materials used as dielectric in ceramic capacitors to extend the current investigations and to deepen the understanding of the physics behind the nonlinear properties of ferroelectric capacitors.
Highlights
The development of implantable medical devices (IMD’s) with application in neurostimulation, known as electroceuticals, has been characterized in recent years by an increasing demand for functionality, reliability and miniaturization
Unlike conventional bulky IMD’s that are consisting of a battery with limited lifetime and wired electrodes, which are susceptible to fracture and migration [1], a new generation of IMD’s emerged in recent years
Neurostimulation has become a proven alternative to conditions where traditional medication treatments fails, such as depression, epilepsy, and chronic intractable pain, to name a few [4]
Summary
The development of implantable medical devices (IMD’s) with application in neurostimulation, known as electroceuticals, has been characterized in recent years by an increasing demand for functionality, reliability and miniaturization. In 2016, the leadless and battery-free tibial nerve stimulator RENOVA from BlueWind Medical (BlueWind Medical Ltd., Herzlia, Israel) received the CE mark to treat overactive bladder [2]. The leadless and battery-free bilateral hypoglossal nerve stimulator Genio from Nyxoah (Nyxoah SA., Mont-Saint-Guibert, Belgium) received the CE mark in 2019 to treat obstructive sleep apnea [3]. Neurostimulation has become a proven alternative to conditions where traditional medication treatments fails, such as depression, epilepsy, and chronic intractable pain, to name a few [4]. An interest in expanding the field of application of neurostimulation, such as for the treatment of autoimmune diseases, can be identified in the literature [5]
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