Flexible Shielded Position Sensor for Medical Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic position sensors in medical devices are prone to electromagnetic interference, which reduces their efficiency, especially when they lack metal electrode coverings, as seen in instruments like ENT tools and guidewires, where electronic low-pass filters are insufficient to remove interference.
Innovation Solution
A flexible printed circuit with alternating conductive and dielectric layers is wrapped around the distal end of medical instruments, featuring a coil with multiple outer layers connected to ground for electromagnetic shielding, effectively acting as a frequency-selective RF shield to filter out higher frequencies while allowing lower frequency signals to pass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a magnetic position sensor is used in a medical device without metal electrode coverings, then the device maintains flexibility and simplicity, but the sensor becomes highly susceptible to electromagnetic interference
Solution Approach 1:
A flexible printed circuit board with ground planes is introduced as an intermediary shielding structure between the magnetic sensor and external electromagnetic sources. The ground planes act as a mediator that redirects electromagnetic interference to ground, protecting the sensor without requiring metal electrode coverings on the instrument itself
Solution Approach 2:
The solution uses a composite structure combining flexible printed circuit board material with conductive ground planes and dielectric layers. This composite construction provides effective electromagnetic shielding while maintaining the flexibility needed for medical instrument applications
2Reliability
If electronic low-pass filters are used to remove interference, then some electromagnetic interference is reduced, but the filters are insufficient to completely eliminate higher frequency interference
Solution Approach 1:
Electromagnetic shielding is implemented before the signal reaches the low-pass filter. The ground planes on the flexible printed circuit board preemptively block higher frequency interference from coupling into the sensor, reducing the burden on subsequent electronic filtering stages
Solution Approach 2:
The solution replaces reliance solely on electronic filtering with a physical electromagnetic shielding approach using conductive ground planes. This mechanical/electrical shielding structure provides frequency-selective attenuation before signals are processed electronically
3Object-affected harmful factors
If multiple outer ground layers are added to the flexible printed circuit, then electromagnetic shielding effectiveness increases, but the manufacturing complexity increases
Solution Approach 1:
The flexible printed circuit is designed with specific parameters for the ground planes including conductivity, area, and spacing optimized for electromagnetic shielding effectiveness. By carefully controlling these parameters, effective shielding is achieved without unnecessarily increasing layer count or manufacturing complexity
Solution Approach 2:
Rather than providing complete 360-degree shielding with multiple layers on all sides of the sensor, ground planes are strategically placed only where electromagnetic interference is most likely to couple into the sensor, providing sufficient protection with minimal additional manufacturing complexity
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
The solution significantly reduces electromagnetic interference, enhancing the accuracy and efficiency of magnetic position sensing by ensuring that only the desired frequency signals are detected, while maintaining flexibility for the sensor to be wrapped around the instrument.
Implementation Method 1
multiple outer layers overlying the at least one inner layer and configured for connection to an electrical ground so as to shield the coil from electromagnetic interference
Implementation Method 2
the conductive layers include at least one inner layer, which is patterned with traces forming a coil
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In one embodiment, a medical device includes an instrument including a distal end configured for inserting into a body part, and a position sensor comprising a flexible printed circuit, which comprises alternating conductive and dielectric layers and is wrapped around the distal end of the instrument, the conductive layers including at least one inner layer, which is patterned with traces forming a coil, and multiple outer layers overlying the at least one inner layer and configured for connection to an electrical ground so as to shield the coil from electromagnetic interference.