BoPET Film Carbon Nanotube Photophoretic Propulsion
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Solution Overview
Problem
Current flight mechanisms are unable to achieve sustained flight in the Earth's mesosphere due to high atmospheric drag and low air density, limiting the practical applications of aircraft and spacecraft in this altitude range, and photophoretic forces generate insufficient lift for practical use.
Innovation Solution
The development of ultrathin materials with unique surface properties, such as biaxially-oriented polyethylene terephthalate (BoPET) films coated with carbon nanotubes, which utilize differences in thermal accommodation coefficients to generate lift forces, even at uniform temperatures, allowing for controlled levitation and potential flight in the mesosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional flight mechanisms are used in the mesosphere, then they can operate at high altitudes, but they cannot achieve sustained flight due to high atmospheric drag and low air density
Solution Approach 1:
The patent replaces conventional aerodynamic lift mechanisms with photophoretic propulsion. The photophoretic engine uses light absorption to create temperature differences that generate thrust through gas molecule momentum transfer, eliminating dependence on aerodynamic forces that are insufficient in the mesosphere. This substitution enables sustained flight where conventional mechanical flight systems fail.
Solution Approach 2:
The patent changes the operating parameters by using selective light absorption to create controlled temperature gradients within the photophoretic engine. By absorbing specific wavelengths of light and converting them to thermal energy, the system generates the necessary thrust parameter changes to overcome atmospheric drag and achieve sustained flight in the mesosphere.
2Force
If photophoretic effect is used to generate lift, then particles can move when illuminated by light, but the force generated is limited to the micronewton range which constrains movable object mass to milligram range or smaller
Solution Approach 1:
The patent changes the physical parameters of the photophoretic engine, including its size, shape, and light absorption properties, to amplify the photophoretic force. By optimizing these parameters and using selective light absorption, the system generates sufficient thrust to overcome gravity and achieve sustained flight with objects of practical mass,突破了 the milligram constraint.
Solution Approach 2:
The patent employs composite structures combining light-absorbing materials with lightweight structural materials. This composite approach maximizes light absorption for photophoretic force generation while minimizing the mass of the movable object, thereby increasing the force-to-mass ratio and enabling practical flight applications.
3Temperature
If ultrathin materials with uniform temperature are used, then temperature differences are eliminated, but lift can still be generated through differences in thermal accommodation coefficient
Solution Approach 1:
The patent applies local quality by creating surfaces with different thermal accommodation coefficients on opposite sides of the ultrathin material. Even though the temperature is uniform throughout, the asymmetric surface properties cause gas molecules to depart with different velocities from each side, generating a net photophoretic force. This local differentiation of surface properties enables lift generation without temperature gradients.
4Force
If BoPET film coated with carbon nanotubes is used, then photophoretic force is enhanced for levitation, but the structure requires additional components for rigidity and stability
Solution Approach 1:
The patent uses flexible ultrathin films coated with light-absorbing materials as the primary structural element. These thin films provide both the photophoretic force generation surface and the basic structural framework, reducing the need for additional rigid support components and simplifying the overall device complexity while maintaining flight 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
The described system enables the levitation and potential flight of structures by enhancing the photophoretic force, allowing for the attachment of additional components and enabling practical applications at various altitudes within the atmosphere.
Implementation Method 1
Photophoresis is an effect wherein particles or other materials can move or be moved when illuminated by light. In the free molecular regime, the photophoretic force can result from the difference in the velocity of incident and departing gas molecules from a heated surface
Implementation Method 2
the lift can be generated through a difference in the thermal accommodation coefficient. Where the thermal accommodation coefficient is larger on the bottom surface of a structure, it can generate a lift force, even if the top and bottom are at approximately the same temperature
Data Source
AI summary
Systems and methods for achieving levitation via a photophoretic effect are provided. In certain embodiments, a structure of ultralight materials is provided, for example a BoPET film and carbon nanotubes and has a top and bottom side, made of two separate materials. When the bottom side is illuminated by light at certain intensity, it can result in an upward lift force being applied to the entire structure, causing the structure to levitate.