Phaco Needle Frequency Tracking for Resonance and Heat Control
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Solution Overview
Problem
Existing phacoemulsification systems face challenges in maintaining optimal needle stroke length and temperature control during cataract surgery, leading to potential eye damage due to inadequate mechanical resonance and heat buildup.
Innovation Solution
A phacoemulsification system that dynamically adjusts the frequency of the drive signal for the piezoelectric actuator based on real-time stroke length measurements using an interferometer, maximizing stroke length and maintaining mechanical resonance to minimize temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the piezoelectric actuator operates at fixed frequency, then the system structure is simple, but the stroke length is suboptimal and temperature control is inadequate
Solution Approach 1:
The system transitions from fixed frequency operation to dynamic frequency adjustment. The controller continuously monitors stroke length via the interferometer and adjusts the drive signal frequency in real-time to maintain optimal resonance conditions, thereby maximizing stroke length while managing temperature.
Solution Approach 2:
The interferometer provides real-time feedback on stroke length to the controller. This closed-loop feedback mechanism enables the system to detect deviations from optimal performance and automatically adjust the drive frequency to correct the deviation, ensuring sustained optimal stroke length.
2Manufacturing precision
If higher vibration amplitude is applied to increase stroke length, then mechanical cutting performance improves, but temperature rise increases causing eye damage
Solution Approach 1:
The system uses periodic vibration at resonant frequency to achieve maximum stroke length with minimal energy input. By synchronizing the drive frequency with the natural resonance frequency of the needle-horn assembly, the system achieves high vibration amplitude through small input forces, thereby reducing heat generation while maintaining effective cutting performance.
Solution Approach 2:
The controller dynamically changes the drive frequency parameter based on real-time stroke length measurements. When stroke length decreases or temperature rises, the system adjusts the frequency to maintain optimal resonance conditions, ensuring that high vibration amplitude is achieved only when mechanically efficient, thus preventing excessive temperature rise.
3Productivity
If the needle vibrates at ultrasonic frequency to emulsify cataract, then surgical effectiveness is achieved, but mechanical resonance is lost leading to reduced stroke length
Solution Approach 1:
The interferometer continuously monitors the actual stroke length of the needle during emulsification and feeds this information back to the controller. When resonance is lost and stroke length decreases, the controller detects this deviation and adjusts the drive frequency to restore resonance, ensuring sustained effective vibration for cataract emulsification.
Solution Approach 2:
The system dynamically tracks and maintains resonance conditions throughout the surgical procedure. As tissue loading and other factors may shift the resonant frequency, the real-time frequency adjustment ensures the needle continues to vibrate at its natural resonance frequency, maximizing stroke length and emulsification effectiveness simultaneously.
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 system effectively maximizes needle stroke length while minimizing probe temperature, ensuring safe and efficient cataract surgery by dynamically adjusting the drive signal frequency.
Implementation Method 1
a piezoelectric actuator disposed in the probe body and configured to vibrate the horn and the needle in one or more directions, e.g. a longitudinal direction, transverse direction, and/or torsional direction, with a stroke length with respect to the probe body
Implementation Method 2
a stroke measurement apparatus configured to provide respective indications of the stroke length of the needle over time
Data Source
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AI summary
A phacoemulsification system including a phacoemulsification probe having a probe body, a horn disposed at least partially in the probe body, a needle coupled with the horn and configured to be inserted into an eye, and a piezoelectric actuator disposed in the probe body and configured to vibrate the horn and the needle in a first direction with a stroke length with respect to the probe body; a signal generator configured to generate a drive signal to drive a vibration of the piezoelectric actuator; a stroke measurement apparatus configured to provide indications of the stroke length of the needle over time; and a controller configured to dynamically adjust a frequency of the drive signal so as to maximize the stroke length and maintain mechanical resonance of the needle responsively to the provided indications of the stroke length.