Capacitive technologies for highly controlled and personalized electrical stimulation by implantable biomedical systems

Abstract

Cosurface electrode architectures are able to deliver personalized electric stimuli to target tissues. As such, this technology holds potential for a variety of innovative biomedical devices. However, to date, no detailed analyses have been conducted to evaluate the impact of stimulator architecture and geometry on stimuli features. This work characterizes, for the first time, the electric stimuli delivered to bone cellular tissues during in vitro experiments, when using three capacitive architectures: stripped, interdigitated and circular patterns. Computational models are presented that predict the influence of cell confluence, cosurface architecture, electrodes geometry, gap size between electrodes and power excitation on the stimuli delivered to cellular layers. The results demonstrate that these stimulators are able to deliver osteoconductive stimuli. Significant differences in stimuli distributions were observed for different stimulator designs and different external excitations. The thickness specification was found to be of utmost importance. In vitro experiments using an osteoblastic cell line highlight that cosurface stimulation at a low frequency can enhance osteoconductive responses, with some electrode-specific differences being found. A major feature of this type of work is that it enables future detailed analyses of stimuli distribution throughout more complex biological structures, such as tissues and organs, towards sophisticated biodevice personalization.

Theoretical and Experimental Investigations of a Pseudo-Magnetic Levitation System for Energy Harvesting

“…Usually, the Finite Element Method has been used to solve the differential equations that govern the dynamics of these systems. Then the magnetic forces, magnetic field distributions are usually easy modelled [25,28]. Mann and Sims [26] presented a design for electromagnetic energy harvesting from the nonlinear oscillations of magnetic levitation.…”

“…Therefore, the magnet vibration centre must be taken into consideration. The detail analysis of the Equation (28) shows that the magnet vibration centre z 0 depends on the magnet oscillation amplitude z 1 .…”

Altering the Course of Technologies to Monitor Loosening States of Endoprosthetic Implants

“…It is pertinent to emphasize that all the proposed acoustic technologies require extracorporeal reading units. This is a significant limitation that shrinks the applicability range and the possibility for continuous interface monitoring, as the electromechanical components attached to the patient's body cause discomfort and troubles in their daily life, which, excluding the latter possibility, limits the technology's operation to the laboratory environment, and in turn disregards the interface state dynamics and does not allow timely delivery of therapeutic stimulation [30]. Mavrogordato et al [65] were the only authors that aimed towards a more sophisticated monitoring system by housing the sensors within the implant's stem, although their technology also requires external units.…”

“…Although these methods are considered accurate techniques to detect loosening states of both cementeless and cemented implants, the clinical follow-up can only be carried out in clinical laboratories, and thus the monitoring cannot be established throughout the daily life of patients. However, future personalized medicine requires technology innovation to trigger the development of advanced implantable devices to simultaneously perform intensive monitoring and actuation operations, to avoid implant failures [18,29,30]. This new technological trend is emerging to implement multifunctional and intelligent orthopedic implants comprising feedback control systems with the ability to enhance bone growth when loosening states are detected [21,29].…”

“…The concept of instrumented implant is an unquestionably disruptive concept that aims to optimize the performance of implants [18,21,29,31]. These are instrumented active technologies incorporating biophysical delivery systems, monitoring systems, wireless communication, and self-powering systems, such that their operation can be controlled by clinicians [18,21,[29][30][31]. For example, this concept can be applied in hip prostheses by incorporating stimulation systems inside the implant (to deliver electromagnetic or mechanical stimuli, among others, to bone structures around the implants), near the proximomedial region where bone loss often occurs, as the stress distribution is usually reduced in this region following arthroplasty [18].…”