Dynamic Skin Cooling with Liquid CO2 and Inert Gas Shielding
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Solution Overview
Problem
Current cryogen cooling methods for laser treatments, such as those using tetrafluoroethane, pose environmental concerns due to high global warming potential and the risk of ignition during pulsed laser exposure, which can cause skin burns.
Innovation Solution
The method involves using a flammable heat transferring substance like liquid propane or butane mixed with inert carbon dioxide, where the mixture is adiabatically expanded to create a slurry that is non-flammable, or employing liquid carbon dioxide under pressure to prevent ignition during electromagnetic radiation exposure by shielding with an inert gas or mixing with an inert substance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If flammable cryogens (propane, butane) are used for cooling, then global warming potential is reduced, but ignition risk during laser exposure increases
Solution Approach 1:
An inert gas (nitrogen or carbon dioxide) is introduced as an intermediary substance between the flammable cryogen and the laser energy. The inert gas forms a protective atmosphere that prevents ignition while allowing the flammable cryogen to perform its cooling function, thereby resolving the contradiction between using low-GWP flammable cryogens and preventing ignition during laser exposure
Solution Approach 2:
The patent creates an inert atmosphere by surrounding the treatment area with nitrogen or carbon dioxide gas. This inert environment eliminates oxygen, preventing combustion of the flammable cryogen during laser exposure while maintaining the cooling effect, thus enabling use of low-GWP cryogens without ignition risk
2Reliability
If inert gas shielding is used to prevent ignition, then safety is improved, but device complexity increases
Solution Approach 1:
The inert gas delivery system serves multiple functions: it acts as a safety barrier against ignition, a cooling assist, and a protective atmosphere during laser exposure. By making the inert gas system multi-functional, the patent reduces overall device complexity while maintaining reliable ignition prevention
Solution Approach 2:
The patent combines the inert gas delivery system with the existing cryogen delivery system, integrating safety functionality into the existing device architecture. This merging approach minimizes additional complexity while achieving reliable ignition prevention through the inert atmosphere
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 approach effectively reduces the global warming potential, prevents ignition, and provides efficient cooling of the skin surface, minimizing the risk of burns while maintaining effective heat transfer coefficients for therapeutic applications.
Implementation Method 1
liquid carbon dioxide under pressure to prevent ignition during electromagnetic radiation exposure by shielding with an inert gas or mixing with an inert substance
Implementation Method 2
selective epidermal cooling can be obtained by exposing the skin surface to a cryogen for an interval of time corresponding to the thermal diffusion time from the stratum corneum through the epidermis and down to the basal layer
Data Source
AI summary
An improvement in a method for providing localized cooling of tissue when thermally mediated by electromagnetic radiation including directing at least one spurt of a heat transferring substance onto a selected location on the tissue, and preventing ignition of the heat transferring substance by heating from the electromagnetic radiation. Preferably liquid carbon dioxide under pressure is supplied as the heat transferring substance, and adiabatically expanded to provide a solid carbon dioxide spray onto the selected location.