Implantable Impedance Sensor Electrode Layout Beyond Scar Tissue
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Solution Overview
Problem
Existing implantable sensors face issues with inaccurate impedance measurements due to body liquids collecting around electrodes, inducing Eddy Currents from PCBs, and measuring in scar tissue rather than healthy tissue, leading to unreliable glucose concentration determination.
Innovation Solution
Optimizing electrode spacing and coil placement, using a ferrite sheet for magnetic shielding, and positioning the coil externally to minimize Eddy Currents and ensure measurements are taken in healthy tissue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sensor is implanted in the body with sharp edges and flat surfaces, then the sensor can be easily manufactured and installed, but body liquids collect around the electrodes causing inaccurate impedance measurements
Solution Approach 1:
The patent applies curvature by replacing sharp edges and flat surfaces with rounded edges and curved surfaces on the sensor housing. This curvature prevents body liquids from collecting around the electrodes by eliminating the sharp corners where liquids would accumulate, thereby maintaining measurement accuracy while preserving manufacturing feasibility
2Ease of operation
If the coil is arranged on or near the printed circuit board, then the sensor can be easily powered, but Eddy Currents are induced in the PCB affecting measurement performance and power transfer
Solution Approach 1:
The patent extracts the coil from its traditional position on or near the printed circuit board and relocates it to an external position. This separation eliminates the Eddy Current problem by removing the source of electromagnetic interference from the PCB area, while power transfer is maintained through optimized coupling between the external coil and the sensor
Solution Approach 2:
The patent introduces an intermediary structure (such as a magnetic shield or optimized coupling mechanism) between the external coil and the sensor to facilitate efficient power transfer while blocking Eddy Current induction in the PCB. This intermediary allows the system to benefit from both close coupling for power transfer and separation for interference avoidance
3Device complexity
If the sensor measures impedance in the immediate surrounding area, then the measurement is simple, but the measurement is taken in scar tissue rather than healthy tissue leading to inaccurate glucose determination
Solution Approach 1:
The patent extends the measurement in the spatial dimension by increasing the distance between current injecting electrodes and voltage sensing electrodes. This dimensional expansion allows the measurement current to penetrate through scar tissue and reach healthy tissue, enabling accurate glucose determination while maintaining measurement simplicity through the four-point measurement method
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
Improves measurement accuracy by reducing interference from body liquids and Eddy Currents, allowing reliable glucose concentration determination beyond scar tissue.
Implementation Method 1
a coil for powering the implantable glucose sensor via a power source
Implementation Method 2
using a ferrite sheet for magnetic shielding
Implementation Method 3
two current injecting electrodes for injecting current into the tissue, two voltage sensing electrodes for measuring impedance in the tissue
Data Source
AI summary
A sensor includes a housing, current electrodes for injecting current into tissue, and voltage electrodes for measuring impedance in the tissue. The voltage electrodes are arranged separately from the current electrodes and in between the current electrodes. A coil powers the sensor via a power source. A circuit board is arranged within the housing. The circuit board is electrically connected to the voltage electrodes, the current electrodes, and the coil. The coil is arranged on top of the circuit board. A communication unit is configured for transferring and receiving data packages and is connected to the circuit board. The housing includes the voltage electrodes and the current electrodes on an outer surface. The sensor includes a ferrite sheet arranged in between the coil and the circuit board. The ferrite sheet has the same or a larger extension as the coil as seen in a plane defined by the circuit board.