This video chronicles the journey of inventing a self-cooling fabric using readily available hardware store parts. Building on previous work with radiative sky cooling coatings, the creator, Ben, aims to develop a flexible fabric capable of maintaining sub-ambient temperatures in direct sunlight. The process involves dissolving polylactic acid (PLA) plastic with polyethylene oxide (PEO) in a solvent, then employing a custom-built fan-based machine to spin and collect fine fibers. Initial success was followed by inconsistencies attributed to cold weather and PEO degradation, leading to the development of a more sophisticated "fiber blowing machine" incorporating heated air, continuous material injection via a DIY swivel connector, and a rotating collection screen.
The optimized PLA fabric demonstrated superior cooling performance, achieving sub-ambient temperatures even without a protective film, surpassing previous cooling paint formulations. However, practical application on a hat revealed challenges with light penetration and thermal conduction, termed the "polar bear effect," where inner layers remained warm despite a cold outer surface. Attempts to improve this with a foil backing showed increased conduction but were hampered by the foil's inherent light absorption. The video concludes by outlining future improvements, such as enhanced opacity and reflectivity, and explores other potential applications like air cooling, thermal camouflage, and even high-performance winter clothing through a "synthetic polar bear effect."
Inventing Self-Cooling Fabric: A Backyard Workshop Journey
0:00Goal: Self-Cooling Fabric: The video aims to invent a self-cooling fabric from common hardware store parts, building on previous radiative sky cooling coatings to create a flexible material for clothing and temporary covers.
1:00Initial Fiber Production Challenges: Previous manual methods for PLA fiber creation were tedious and produced brittle fibers, though they proved the concept of radiative cooling.
2:00DIY Fiber Blower (Version 1): An inline ventilation fan was modified with a container and pinholes to eject fibers from a dissolved PLA solution.
3:00Material Composition: PLA is dissolved in ethyl acetate, with polyethylene oxide (PEO) added to make the solution stringy.
4:00First Successful Fabric Creation: The initial fan setup successfully produced thin fibers that collected on a window screen, forming a nonwoven fabric similar to a coffee filter.
8:00Inconsistent Results & Environmental Impact: Subsequent attempts faced issues with the plastic solution becoming too gooey ("snot") and freezing in colder weather.
9:00Advanced Fiber Blowing Machine (Version 2): A new machine was built with key improvements: hot air input to prevent freezing, a hollow shaft for continuous material injection via a DIY Teflon swivel connector, and variable spinning head speed control.
13:00Why PLA? PLA is chosen for its excellent natural infrared emission spectrum (matching the atmospheric infrared window), its bioplastic nature, and its UV breakdown (requiring future coatings).
15:00Solving the "Snot" Problem: The inconsistency was traced to the degradation of PEO molecular chains over time. Switching to a shorter chain-length PEO (1 million g/mol) provided immediate and consistent success.
17:00Improved Fabric Strength and Size: A rotating collection screen was implemented, causing fibers to overlap in a spirograph-like pattern, resulting in a stronger fabric in all directions and enabling larger pieces.
18:00Optimized Fabric Recipe: A detailed recipe for bright, fine, flexible, and strong fibers is provided, using PLA pellets and a solvent mixture that creates nanovoids for light scattering.
20:00Exceptional Cooling Performance: The new PLA fabric outperformed previous homemade cooling paints and ordinary white cotton, uniquely achieving sub-ambient temperatures even in direct sunlight without a protective film.
22:00Hat Application & "Polar Bear Effect": Applying the fabric to a hat brim revealed a challenge: light penetrating the porous fabric warmed underlying layers and the hat itself, while poor thermal conduction prevented this heat from dissipating through the cold outer surface.
25:00Foil Backing Trial: Backing the fabric with aluminum foil improved thermal conduction but the foil's 15% sunlight absorption was too high, overwhelming the fabric's cooling capabilities.
27:00Future Directions & Potential Applications: Future improvements will focus on more reflective backings, increased fabric opacity, or enhanced cooling power (possibly with pigment). Other applications explored include air cooling, thermal camouflage (outer surface staying dark), and high-performance winter clothing using a "synthetic polar bear effect" to retain heat.