Probe Contact Detector Strain Gauge Sensor Design
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Solution Overview
Problem
Probes with cantilever arms used for determining electrical properties of test samples are prone to damage due to misalignment and surface imperfections, and existing contact detectors based on piezoresistive materials struggle to distinguish between force magnitude and direction, leading to inaccurate distance measurements and electrical property determinations.
Innovation Solution
A probe with cantilever arms and a contact detector featuring a strain gauge sensor made from non-piezoresistive materials, where the contact detector is designed to detect surface contact before or simultaneously with the cantilever arms, using a flexible arm split at its base and an electrical pathway through anchoring arms to minimize damage and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoresistive materials are used in contact detectors, then force detection capability is provided, but the ability to distinguish between force magnitude and direction is lost leading to inaccurate distance measurements
Solution Approach 1:
The contact detector is divided into multiple independent strain gauge sensors arranged in specific orientations. Each sensor measures force components in different directions, allowing the system to distinguish between force magnitude and direction by analyzing the pattern of responses across the segmented sensors.
Solution Approach 2:
The patent replaces piezoresistive materials with strain gauge sensors that use electrical resistance changes in flexible conductive paths rather than relying on piezoresistive effects. This substitution enables directional force component measurement through geometric arrangement of the strain gauges, resolving the ambiguity present in piezoresistive-based detection.
2Reliability
If the probe is brought into contact with the test sample surface, then electrical property determination is enabled, but damage to the cantilever arms occurs due to misalignment and surface imperfections
Solution Approach 1:
The contact detector is positioned to make contact with the test sample surface before the cantilever arms. This preliminary action serves as an early warning system that detects surface contact and prevents the cantilever arms from encountering damaging surface imperfections or misalignment issues.
Solution Approach 2:
The contact detector acts as an intermediary element between the probe body and the cantilever arms. It absorbs the initial contact forces and provides feedback to control the probing process, protecting the sensitive cantilever arms from direct exposure to harmful surface conditions.
3Measurement precision
If the contact detector is made insensitive to forces perpendicular to the surface normal, then distance measurement accuracy is improved, but the ability to detect all contact forces is reduced
Solution Approach 1:
The strain gauge sensors are oriented with their sensitive axes aligned parallel to the surface normal direction. This local quality configuration ensures that each sensor primarily responds to force components in the normal direction while being insensitive to perpendicular forces, enabling accurate distance measurements through selective force component detection.
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 effectively reduces probe damage and enhances the accuracy of distance measurements and electrical property determination by using a strain gauge sensor insensitive to forces perpendicular to the surface normal, allowing for precise contact detection and improved reliability.
Implementation Method 1
The change in resistance with respect to the applied force is known to be non-linear. It is also known that, under favourable circumstances, the corresponding non-linearity in the resulting detection signal can be compensated for by electronic or digital means.
Implementation Method 2
an electrical pathway of a non-piezoresistive material going out through one of the anchoring arms to the flexible arm and back through the other of the anchoring arms
Data Source
AI summary
The present invention relates to a probe for determining an electrical property of an area of a surface of a test sample, the probe is intended to be in a specific orientation relative to the test sample. The probe may comprise a supporting body defining a first surface. A plurality of cantilever arms (12) may extend from the supporting body in co-planar relationship with the first surface. The plurality of cantilever arms (12) may extend substantially parallel to each other and each of the plurality of cantilever arms (12) may include an electrical conductive tip for contacting the area of the test sample by movement of the probe relative to the surface of the test sample into the specific orientation. The probe may further comprise a contact detector (14) extending from the supporting body arranged so as to contact the surface of the test sample prior to any one of the plurality of cantilever arms (12) contacting the surface of the test sample when performing the movement.