Surgical Force Sensor Substrate Groove Segmentation
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Solution Overview
Problem
Force sensors for surgical devices face issues with durability under large loading forces, premature failure due to strain-induced deformation, and inaccuracy from permanent deformation of substrates, as well as potential failure of solder connections and cracking of glass substrates.
Innovation Solution
A force sensor substrate design featuring a planar distal surface with grooves that separate load contact areas from sensing areas, minimizing strain on sensing elements and preventing damage to coatings and solder connections, while allowing for easier masking and coating separation, enhancing durability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the substrate is subjected to large loading forces, then the force sensor can measure higher forces, but the substrate undergoes permanent deformation causing inaccurate readings
Solution Approach 1:
The substrate is segmented into distinct regions: a load-bearing structure and a sensing area. The groove physically separates the distal load contact area from the sensing area, allowing the substrate to be loaded at the distal end while the sensing area remains undeformed and maintains accurate measurements.
Solution Approach 2:
The groove acts as an intermediary element that transfers the load away from the sensing area. It creates a strain shadow zone that protects the sensing elements from direct loading, enabling the sensor to measure force without the substrate deforming under the measurement location.
2Device complexity
If solder connections are made in areas of high strain, then the sensor can be compact, but the solder connections fatigue and fail under repeated loading
Solution Approach 1:
The groove divides the substrate into high-strain and low-strain zones. Solder connections are placed in the low-strain sensing area or at the proximal end where strain is minimal, while the distal load contact area maintains high strain for force measurement. This segmentation isolates the solder joints from the high-strain environment, preventing fatigue.
Solution Approach 2:
The groove serves as a protective intermediary that shields the solder connections from the high-strain environment. It creates a physical barrier that prevents strain propagation to the solder pads, ensuring their long-term reliability under repeated loading conditions.
3Ease of manufacture
If glass is used along the substrate for vapor deposition, then the sensor can be fabricated with thin films, but the glass cracks when loaded
Solution Approach 1:
The substrate design segments the load path away from the glass-coated sensing area. The groove creates a separation where the glass layer can be deposited on the sensing area without being subjected to direct loading forces, preventing crack formation while maintaining the benefits of vapor deposition fabrication.
Solution Approach 2:
The groove acts as a protective intermediary that protects the glass-coated sensing area from mechanical loading. It creates a strain shadow that prevents stress concentration at the glass-substrate interface, allowing the glass to be deposited and remain intact under loading conditions.
4Speed
If the sensing area is directly exposed to load contact, then the sensor responds quickly to force changes, but the sensing elements and coatings are damaged by strain
Solution Approach 1:
The groove creates a physical segmentation between the load contact area and the sensing area. This allows the sensing elements to detect force changes indirectly through the groove structure, maintaining quick response while protecting the elements from direct strain damage.
Solution Approach 2:
The groove serves as an intermediary that transmits force information to the sensing elements without directly exposing them to high strain. It acts as a strain shield that allows the sensing area to respond to force changes while maintaining the integrity of the coatings and elements.
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 substrate configuration enables force sensors to withstand large loading forces without disrupting sensing electronics, prevents premature failure, and maintains accuracy, making them more durable for reuse and resistant to environmental stresses like autoclaving.
Implementation Method 1
The strain gauge is incorporated in a Wheatstone Bridge Circuit configuration and includes an excitation voltage. The circuit is designed to be at balance before deflection (i.e., no load) and the circuit will have a resistance at zero load. During loading, the beam will deflect and the strain gauge will produce a resistance change.
Implementation Method 2
Some strain gauges incorporate a thin plastic film with a bonded NiCr (nickel-chromium or nichrome) wire path embedded on the film. When the film is bonded to the beam and the beam is deflected, the NiCr wire will also be subjected to bending causing a deformation of the wire. The deformation of the wire will cause the above mentioned change in electrical resistance.
Implementation Method 3
The strain gauge is incorporated in a Wheatstone Bridge Circuit configuration and includes an excitation voltage. The circuit is designed to be at balance before deflection (i.e., no load) and the circuit will have a resistance at zero load.
Data Source
AI summary
The present disclosure relates to force sensors and force sensor substrates for use with surgical devices.