Flexible Capacitive Force Sensor for Surgical Instruments
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Solution Overview
Problem
Conventional force sensors are not viable for small-scale objects, such as surgical instruments, due to their size and flexibility, making it difficult to accurately measure forces applied to these objects, especially in minimally invasive procedures where tactile feedback is limited.
Innovation Solution
A flexible force sensor system using capacitive sensing components with movable electrode plates in a non-conductive material, assembled in a housing that allows for variable gaps to detect changes in force, enabling accurate measurement of force magnitude and direction through an LC circuit and impedance detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional force sensors are used, then force measurement capability is provided, but the sensor size is too large for small-scale objects like surgical instruments
Solution Approach 1:
The patent employs flexible printed circuit boards (FPC) as the substrate for mounting strain gauges, allowing the sensor to conform to small-scale curved surfaces of surgical instruments. This flexible film approach enables force sensing on objects with limited surface area while maintaining measurement capability.
Solution Approach 2:
The force sensor is divided into multiple discrete strain gauge elements arranged in a bridge configuration on the flexible circuit. This segmentation allows the total sensing function to be distributed across small components that can be mounted on limited surface area while collectively providing accurate force measurement.
2Adaptability or versatility
If the surgical instrument is made flexible or resilient, then minimally invasive insertion is enabled, but force transfer from distal to proximal end is compromised
Solution Approach 1:
The patent replaces direct mechanical force transfer through the instrument shaft with an electromagnetic sensing system. Strain gauges mounted on flexible circuits detect local deformations and convert them to electrical signals, which are then processed to determine distal end forces without requiring rigid mechanical force transmission.
Solution Approach 2:
The flexible printed circuit board with strain gauges acts as an intermediary between the flexible instrument structure and the force measurement system. It captures mechanical deformations at multiple points along the instrument and translates them into measurable electrical signals, bridging the gap between instrument flexibility and force sensing accuracy.
3Adaptability or versatility
If the distal end is inserted through a small incision, then minimally invasive access is achieved, but direct visual and tactile feedback is lost
Solution Approach 1:
The patent implements a feedback system where strain gauge measurements from multiple locations on the instrument are continuously monitored and processed. This provides real-time information about forces at the distal end, compensating for the loss of natural tactile feedback that the surgeon would otherwise feel through a rigid instrument.
Solution Approach 2:
The patent replaces the surgeon's natural tactile sense with an electronic sensing and signal processing system. Strain gauges convert mechanical deformations into electrical signals that are amplified and processed to provide quantitative force information, substituting the lost tactile feedback channel with an electronic information pathway.
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 system effectively measures and determines the magnitude and direction of forces applied to small-scale objects, even in flexible or resilient materials, providing reliable data for surgical instruments and other small-scale applications.
Implementation Method 1
respective ones of the first electrode plates are aligned and parallel to, yet spaced from, respective ones of the second electrode plates to establish a plurality of capacitive sensing components
Implementation Method 2
an LC circuit and impedance detection
Data Source
AI summary
Methods of manufacturing a flexible force sensor include forming a first sensor part providing a plurality of spaced first electrode plates in an electrically non-conductive material. A second sensor part is also formed and includes a plurality of second electrode plates in an electrically non-conductive material. The second electrode plates are identical to the first electrode plates at least in terms of spacing. The first part is assembled to the second part such that each of the first electrode plates are aligned with and parallel to, yet spaced from, respective ones of the second electrode plates, establishing a plurality of capacitive sensing components. The first electrode plates are movable relative to the corresponding second electrode plates, establishing a variable gap therebetween. The sensor parts can be ring-shaped. The sensor parts can be formed via MEMS techniques, with the non-conductive material being a polymer.