Faraday Cage Strain Gauge Sensor for Surgical Instruments
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Solution Overview
Problem
Surgical instruments equipped with fiber Bragg grating sensors are prone to degradation when exposed to autoclave cleaning, requiring recalibration and reducing their useful life due to the failure of epoxy glue used for attachment.
Innovation Solution
A surgical instrument with a force sensor apparatus that includes a Faraday cage configuration, utilizing a sensor capsule with strain gauges mounted as a cantilever beam and amplifier circuit to measure forces, which is immune to cautery noise and autoclave processes, eliminating the need for fiber optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fiber Bragg Grating sensors are used in surgical instruments, then force measurement capability is achieved, but the sensors degrade during autoclave cleaning requiring recalibration
Solution Approach 1:
The patent replaces the fragile Fiber Bragg Grating sensors with strain gauges that are significantly more durable and can withstand autoclave cleaning processes. While strain gauges are simpler and less expensive components, they provide the necessary force measurement capability without the degradation issues of fiber optic sensors, effectively treating the sensing system as a robust, replaceable component rather than a delicate, long-lasting one.
Solution Approach 2:
The patent changes the fundamental measurement parameter from optical (Fiber Bragg Grating reflectivity) to electrical (strain gauge resistance). This parameter change allows the sensing system to be immune to autoclave cleaning effects, as electrical strain gauges do not suffer from the epoxy glue degradation that plagues optical fiber sensors during sterilization processes.
2Measurement precision
If Fiber Bragg Grating sensors are used, then force sensing is enabled, but epoxy glue degradation limits useful life
Solution Approach 1:
The patent replaces the fragile Fiber Bragg Grating sensors with strain gauges that are significantly more durable and can withstand autoclave cleaning processes. While strain gauges are simpler and less expensive components, they provide the necessary force measurement capability without the degradation issues of fiber optic sensors, effectively treating the sensing system as a robust, replaceable component rather than a delicate, long-lasting one.
Solution Approach 2:
The patent substitutes the optical measurement system (Fiber Bragg Gratings) with a purely mechanical/electrical system (strain gauges). This replacement eliminates the need for optical fibers and epoxy adhesives that degrade during autoclave cleaning, thereby extending the useful life of the surgical instrument through repeated sterilization cycles.
3Measurement precision
If Fiber Bragg Grating sensors are used, then force measurement is achieved, but recalibration is required after cleaning
Solution Approach 1:
The patent replaces the fragile Fiber Bragg Grating sensors with strain gauges that are significantly more durable and can withstand autoclave cleaning processes. While strain gauges are simpler and less expensive components, they provide the necessary force measurement capability without the degradation issues of fiber optic sensors, effectively treating the sensing system as a robust, replaceable component rather than a delicate, long-lasting one.
Solution Approach 2:
The strain gauge system is designed to maintain its calibration automatically through autoclave cleaning processes, unlike Fiber Bragg Grating sensors that require manual recalibration. The electrical strain gauges inherently resist the chemical and thermal effects of sterilization, providing self-maintaining measurement accuracy without requiring intervention or recalibration procedures.
4Object-affected harmful factors
If strain gauges are mounted in a Faraday cage, then immunity to cautery noise is achieved, but device complexity increases
Solution Approach 1:
The Faraday cage structure serves multiple functions simultaneously: it provides electromagnetic shielding against cautery noise, maintains a controlled environment for the strain gauges, and acts as part of the mechanical structure of the force sensor. By combining these functions into a single component, the patent reduces overall device complexity despite the added shielding requirement.
Solution Approach 2:
The patent merges the electromagnetic shielding function with the mechanical housing of the force sensor. The Faraday cage is integrated into the sensor capsule structure, combining the protective shielding function with the structural support function, thereby minimizing the increase in device complexity while achieving cautery noise immunity.
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 provides a reliable and long-lasting force sensing capability in surgical instruments, resistant to autoclave cleaning and cautery noise, without the need for recalibration, ensuring accurate force measurements during surgical procedures.
Implementation Method 1
A strain gauge is mounted within the sensor capsule
Implementation Method 2
The sensor capsule is part of a Faraday cage. The tube and the electronics enclosure complete the Faraday cage
Implementation Method 3
The sensor capsule is configured as a cantilever beam. The strain gauge is mounted on an interior wall of the cantilever beam
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A surgical instrument includes a force sensor apparatus that is immune to noise from arcing cautery without relying on fiber optic strain gauges, and that is autoclabable. The surgical instrument includes a housing, a shaft, the force sensor apparatus, a joint, and an end component. The force sensor apparatus includes at least one strain gauge that is enclosed in a Faraday cage. The Faraday cage includes a sensor capsule that includes one or more strain gauges, a cable shield tube connected to the sensor capsule, and an electronics enclosure connected to the cable shield tube. The sensor capsule is positioned between the joint and the shaft. The cable shield tube extends through the shaft to the electronics enclosure that is within the housing.