Diamond Window Bonding in Laser Tools
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Solution Overview
Problem
Diamond windows in laser tools tend to de-bond from the tubular body due to thermal mismatch, leading to potential tissue damage during medical procedures, as the diamond window expands differently than the stainless steel tubular body, exacerbated by heating during use and sterilization processes.
Innovation Solution
The tubular body is made from a material with a low thermal expansion coefficient and high thermal conductivity, such as molybdenum, with a metallization coating and a braze join to securely bond the diamond window, reducing thermal stress and preventing delamination, and the diamond window is positioned in a recess to avoid sharp edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diamond window is bonded to a stainless steel tubular body, then the laser tool can transmit high power laser beams, but the diamond window de-bonds from the tubular body due to thermal expansion mismatch
Solution Approach 1:
The patent changes the material parameter (coefficient of thermal expansion) of the tubular body from stainless steel to a material with low thermal expansion coefficient that closely matches diamond. This parameter change resolves the thermal expansion mismatch between the diamond window and tubular body, preventing de-bonding while maintaining laser transmission capability
Solution Approach 2:
The patent employs a composite material solution by using a tubular body made of a specialized low thermal expansion material that is bonded to a diamond window. This composite structure combines the high laser transmission properties of diamond with the thermal expansion compatibility of the specialized tubular body material, creating a reliable bonded joint
2Volume of moving object
If the end tip is made small for minimally invasive surgery, then the laser tool can be inserted into narrow passages, but the end tip heats up rapidly during operation
Solution Approach 1:
The patent changes the thermal property parameter of the end tip by using a material with high thermal conductivity for the tubular body. This allows the small end tip to maintain low temperature during operation by efficiently conducting heat away, enabling minimally invasive surgery while preventing excessive heating
3Reliability
If autoclaving is used to sterilize the apparatus, then the device can be sterilized between uses, but the thermal stress exacerbates the de-bonding problem
Solution Approach 1:
The patent changes the thermal expansion parameter of the tubular body material to match diamond's low thermal expansion coefficient. This parameter change ensures that during autoclaving sterilization, both the diamond window and tubular body expand at similar rates, minimizing thermal stress and preventing bond failure while maintaining sterilization capability
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
This configuration enhances the stability and reliability of the laser tool, reduces the risk of diamond window delamination, and prevents tissue damage by effectively managing heat and maintaining a secure bond between the diamond window and the tubular body.
Implementation Method 1
The increase in temperature causes the diamond window and the tubular body to expand at different rates causing stress at the join between the diamond window and the tubular body. This is because diamond has a much lower coefficient of thermal expansion compared with standard materials used to form the tubular body such as stainless steel.
Implementation Method 2
a braze join is provided between the metallization coating and the tubular body bonding the diamond window to the tubular body to form a seal all around the aperture
Implementation Method 3
diamond has a much lower coefficient of thermal expansion compared with standard materials used to form the tubular body such as stainless steel. If the stress becomes too large, then the join fails and the window de-bonds from the tubular body.
Data Source
Figure 1~6
AI summary
A component for a laser tool, the component comprising: a tubular body defining an internal channel and an aperture; and a window disposed across the aperture and bonded to the tubular body around the aperture, wherein the window is diamond, and wherein the tubular body comprises a material having a coefficient of linear thermal expansion a of 14 x 10-6 K-1 or less at 20°C and a thermal conductivity of 60 Wm-1K-1 or more at 20 °C.