Anyone who has had to comb their long hair knows how difficult it can be trying to untangle tangles. But mathematicians have proven what many had suspected for a while: The key to unraveling knots is starting at the ends and working your way up to the roots.
Harvard researchers created a model simulating two helically entwined filaments (similar to a strand of DNA) to represent a hair knot, and analyzed different ways of brushing hair to release it.
The results of the research, published in the journal Soft Matter, showed that short brushstrokes starting from the free end of the hair and moving towards the clamped end were the most effective way.
Plumb-Reyes, a graduate student at SEAS, said, “Using this minimal model, we study how knots are untied by a single hard tooth (fork) moving over the double helix, leaving behind two untied filaments.” “We measured the scan-related forces and deformations and then simulated them numerically.”
Also, as researchers warn, using the wrong brushing strategy can be very painful and damaging to the hair, as well as take much longer to remove all tangles
Professor Lakshminarayanan Mahadevan (CORR), co-author of the study ), she said she learned the mechanics of combing years ago while combing her little daughter’s hair: “I remember detangling spray sometimes worked, but I still had to be careful to comb gently, starting at the free ends. But I was fired from this job soon after because I wasn’t very patient.”
In their next research, the team aims to examine the mechanics of brushing curly hair and how it responds to humidity and temperature.
also inspired MIT scientists
The mathematical principles of brushing developed by Mahadevan and his team were recently used by researchers at MIT to design algorithms for brushing hair with the help of a robot. Dubbed ‘RoboWig’, the robot has a camera that helps it see and evaluate knots so it can plan a precise and time-efficient scrubbing. “By developing a model of knotted fibers, we understand how hair should tangle from a model-driven perspective,” says Josie Hughes, postdoctoral researcher in the MIT Computer Science and Artificial Intelligence Lab
and lead author of a paper on RoboWig. “Start at the bottom and work your way up slowly to avoid pinching the fibers. It’s something everyone who combs their hair has learned from experience, but now we can demonstrate through a model and use to inform a robot.”
So far, the robot has only been tested on wigs to gain insight into how brushing techniques affect different hairstyles and types. However, the team wants to conduct more realistic experiments on humans to better understand the robot’s performance relative to its painful experience.
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