Variable Stiffness Rack for Physiological Signal Measurement
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Solution Overview
Problem
Existing physiological signal measurement devices face challenges in achieving accurate pulse signal acquisition due to signal absorption by muscles and fats, which affects the depth of artery detection and sensor sensitivity.
Innovation Solution
A physiological signal measurement device with a rack having different stiffness at each end, allowing sensors to be pressed into the skin at varying depths, compensating for tissue absorption and improving accuracy by considering the shape of the limb and artery depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensors are attached onto the user's skin with good adhesion, then the sensor stability is improved, but the measurement precision deteriorates due to signal absorption by muscles and fats
Solution Approach 1:
The rack is designed with non-uniform stiffness distribution, where the first end has higher stiffness than the second end. This creates different local mechanical properties at different positions, allowing the first sensor to press deeper into the tissue to reach arteries while the second sensor maintains shallower contact. This local differentiation resolves the contradiction by enabling each sensor to operate at its optimal depth for detecting pulse signals.
Solution Approach 2:
The rack employs asymmetric stiffness design where the first end stiffness is higher than the second end stiffness. This asymmetric structure causes the first end to deform less and press the first sensor deeper into the tissue, while the second end deforms more and keeps the second sensor at a shallower position. This asymmetry directly addresses the measurement precision issue by compensating for varying tissue absorption at different depths.
2Measurement precision
If the rack has high stiffness at both ends, then the sensor contact depth is improved, but the device complexity increases due to non-uniform stiffness design
Solution Approach 1:
The rack's stiffness parameter is changed non-uniformly along its length, with the first end having higher stiffness and the second end having lower stiffness. This parameter variation is achieved through structural design differences at each end, such as varying thickness or material distribution. This approach improves sensor contact depth by ensuring the first sensor reaches the artery while keeping the overall rack structure relatively simple through controlled parameter variation.
3Measurement precision
If the rack has non-uniform stiffness distribution, then the measurement precision is improved by compensating tissue absorption, but the manufacturing precision requirements increase
Solution Approach 1:
The rack is designed with distinct local regions having different stiffness characteristics. The first end region is structured to be stiffer than the second end region, creating localized mechanical properties that compensate for tissue absorption variations. This local quality approach improves measurement precision while allowing relatively relaxed manufacturing tolerances overall, as only specific regions require precise stiffness control rather than the entire structure.
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 device enhances the accuracy of physiological signal measurement by ensuring sensors detect signals at optimal depths, reducing absorption by tissues and improving overall measurement precision.
Implementation Method 1
both ends of the rack are configured to receive acoustic wave sensors, respectively
Data Source
AI summary
A physiological signal measurement device is disclosed. In some implementations, the physiological signal measurement device includes a fixing element, a rack, a first sensor, and a second sensor. The fixing element is configured to be fixed on a limb of a user. The rack is configured to engage the fixing element and includes a first end and a second end distal to the first end. The first sensor is disposed on the first end of the rack. The sensor is disposed on the second end of the rack. The first end of the rack has a first stiffness, the second end of the rack has a second stiffness, and the first stiffness is higher than the second stiffness.