Implantable Pressure Sensor EMI Shielding via Conductive Coating
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Solution Overview
Problem
Implantable medical electrical leads with pressure sensors are susceptible to electromagnetic interference (EMI) due to the presence of unshielded and ungrounded electronic components, which can lead to parasitic capacitance and charge buildup, resulting in measurement errors and drift.
Innovation Solution
The integration of a conductive coating over the sidewall of the pressure sensor to provide EMI shielding and grounding, which includes a conductive layer extending over the exterior surface of the sensor to drain away excess charge and prevent parasitic capacitance, while maintaining the flexibility of the pressure-sensitive diaphragm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hermetically sealed capsule containing a gap capacitor and IC chip is used as a pressure sensor, then the sensor provides reliable pressure measurement capability, but the unshielded electronic components are susceptible to electromagnetic interference and charge buildup
Solution Approach 1:
A conductive coating is applied to the exterior surface of the hermetically sealed capsule to serve as an intermediary EMI shield. This conductive layer acts as a mediator between the sensitive electronic components inside the capsule and the external electromagnetic environment, redirecting electromagnetic interference and excess charge away from the capsule without compromising the hermetic seal or pressure measurement functionality.
Solution Approach 2:
The conductive coating is applied in advance to the capsule exterior to prevent electromagnetic interference and charge buildup before they can affect the electronic components. This preliminary protective action creates a shield that actively counteracts harmful electromagnetic effects before they penetrate to the sensitive IC chip and capacitor inside the capsule.
2Ease of operation
If the capsule sidewall is made thin to maintain flexibility of the pressure-sensitive diaphragm, then the diaphragm remains flexible for accurate pressure sensing, but the capsule provides less structural protection and EMI shielding
Solution Approach 1:
The solution moves the EMI shielding function from the capsule wall thickness dimension to an external coating dimension. By applying a conductive coating on the exterior surface of the capsule, the patent provides EMI protection and structural reinforcement without increasing the capsule wall thickness, thereby preserving the flexibility of the pressure-sensitive diaphragm while adding protective functionality in a different dimensional space.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively shields the pressure sensor from EMI, preventing measurement errors and ensuring accurate pressure readings even in aqueous environments, such as bodily fluids, by draining away excess charge and reducing the impact of radiated EMI.
Implementation Method 1
a conductive layer extending over the exterior surface of the sensor to drain away excess charge
Implementation Method 2
The integration of a conductive coating over the sidewall of the pressure sensor to provide EMI shielding and grounding
Data Source
AI summary
An implantable pressure sensor, which may be incorporated within an implantable medical electrical lead, includes an insulative sidewall, which contains a gap capacitor and an integrated circuit. The insulative sidewall of the pressure sensor includes a pressure sensitive diaphragm portion, and the gap capacitor includes a first electrode plate, which is attached to an interior surface of the diaphragm portion of the sidewall, and a second electrode plate, which is spaced apart from the first electrode plate and coupled to the integrated circuit, which is coupled, through the sidewall, to a supply contact and a ground contact. A conductive layer extends over one of the interior surface of the diaphragm portion of the sidewall and an exterior surface of the diaphragm portion; and the conductive layer is coupled to the ground contact to either shield or ground the first electrode plate.