Flexible Optical Probe Strain Relief for Interconnection Durability
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Solution Overview
Problem
Flexible medical apparatuses used for measuring optical or physiological parameters, such as near-infrared spectroscopy oximeters for infants, often fail due to cracks and ruptures in electrical interconnections caused by repeated bending, posing a critical risk to vital parameter monitoring.
Innovation Solution
Incorporation of a bendable strain relief device with two tensile stress lines spaced apart to absorb and distribute tensile forces, protecting the electrical interconnections from excessive stress and maintaining flexibility for effective skin contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the apparatus is made flexible to conform to curved surfaces (e.g., infant heads), then adaptability and ease of application are improved, but the electrical interconnection becomes susceptible to cracks and ruptures due to repeated bending
Solution Approach 1:
The interconnection is segmented into multiple layers including a flexible substrate layer, conductive track layer, and protective coating layers. This segmentation allows each layer to handle specific mechanical stresses independently, preventing crack propagation through the entire structure while maintaining flexibility for conforming to curved surfaces.
Solution Approach 2:
The interconnection uses composite material structures combining flexible substrates (e.g., polyimide or polyester) with conductive traces and protective coatings. This composite construction provides both the flexibility needed for bending and the mechanical strength to prevent rupture, resolving the contradiction between adaptability and reliability.
2Reliability
If the interconnection is made more robust to prevent cracks, then reliability is improved, but flexibility and bendability of the apparatus are reduced
Solution Approach 1:
The interconnection employs flexible thin film substrates (such as polyimide or polyester films) that inherently provide both mechanical strength and flexibility. These thin films can withstand repeated bending cycles while maintaining interconnection integrity, allowing the apparatus to conform to curved surfaces without compromising reliability.
Solution Approach 2:
The substrate material parameters are optimized by selecting materials with specific mechanical properties (e.g., elongation at break, modulus of elasticity) that balance flexibility and strength. By changing material parameters rather than increasing thickness, the interconnection maintains robustness while preserving the apparatus's ability to bend and conform to curved surfaces.
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 strain relief device significantly reduces the occurrence of ruptures and cracks, enhancing the apparatus's robustness and longevity, ensuring reliable measurements and preventing total system failure.
Implementation Method 1
the strain relief device is configured to transmit tensile stress from the electronic unit to the carrier substrate along said longitudinal axis
Implementation Method 2
the strain relief device offers two tensile stress lines, which are spaced from each other... configured to transmit tensile stress... to take up and deliver tensile forces applied between the carrier substrate and the electronic unit
Data Source
Figure 1~3
Figure 4~6
Figure 7~9
AI summary
Several measures are suggested for improving the durability and lifetime of an elongated and bendable apparatus (1) designed for measuring an optical or physiological parameter in a scattering medium, featuring an interconnection (8) linking an electronic unit (7) at a proximal end (6) of the apparatus (1) to a carrier substrate (4), bearing a light source (2) and detector (3), at a distal end (5) of the apparatus (1). These measures include a strain relief device (12) offering two separate stress lines (13a, 13b) for transmitting tensile stress from a pair of spaced anchoring points (14a, 14b) at the electronic unit (7) to a pair of spaced anchoring points (14c, 14d) at the measuring circuit board (4), an electronic rupture detection device (33) configured to detect the formation of ruptures in the interconnection (8), and a stiff reinforcement element (29) located remote from and proximal to the carrier substrate (4) for mechanically supporting the interconnection (8) in the area of a fan-out (c.f. Fig. 5).