Wearable Pulse Wave Sensor Band with Anisotropic Stretchability
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Solution Overview
Problem
Existing biometric information measurement devices face challenges in securely attaching to the wrist due to the presence of the ulna, leading to potential displacement of the pressure sensor and inaccurate measurements, especially when using highly stretchable bands.
Innovation Solution
A pulse wave detector with a strip-shaped band member that includes a first region of lower stretchability and a second region of higher stretchability, where the second region contacts the ulna or radius, ensuring stable attachment and minimizing displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a highly stretchable material is used in the band, then the feeling and easiness of attachment of the device can be improved, but after the device is secured to the wrist, displacement of the position of the pressure sensor portion may be caused by stretching or contraction of the band portion
Solution Approach 1:
The band is designed with different stretchability in different directions: high stretchability in the longitudinal direction (easy to put on) and low stretchability in the width direction (prevents sensor displacement). This local differentiation of mechanical properties resolves the contradiction between ease of attachment and position stability.
2Ease of operation
If the body portion is placed to avoid the ulna process, then the band can be fastened without interference, but the pressure sensor position may be displaced by hand motion
Solution Approach 1:
The band has differentiated stretchability where the width-direction stretchability is specifically reduced in the region that contacts the ulna process. This allows the band to accommodate the ulna's protrusion while maintaining sufficient grip to prevent sensor displacement during hand motion.
3Ease of operation
If the band is made highly stretchable, then attachment comfort is improved, but measurement accuracy deteriorates due to sensor displacement
Solution Approach 1:
The band's anisotropic stretchability (high in longitudinal direction, low in width direction) allows comfortable attachment while maintaining precise sensor positioning. The low width-direction stretchability specifically prevents sensor displacement that would compromise pulse wave detection accuracy.
Data Source
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AI summary
Provided are: a pulse wave detection device that improves wearing comfort and wearability on the wrist and can detect pulse waves with high accuracy; and a biometric information measurement device equipped with the pulse wave detection device. The biometric information measurement device 100 used while worn on the wrist H is provided with: a main body part 20 that includes a pulse wave detection sensor for detecting a pulse wave from the artery of a person to be measured; and a belt-like band member 3 for fixing the main body part 20 to the wrist H. In a fixed state of being fixed to the wrist H with the band member 3, the main body part 20 is disposed at a position that allows a protrusion Sa of the ulna to be exposed. The band member 3 includes a first region 3A and a second region 3B having a greater stretchability than the first region 3A. The second region 3B comes into contact with at least the protrusion Sa of the ulna in the fixed state.