5 Top Tips for Going Viral with Leidenfrost Physics

A short video showing a water droplet moving towards the right of the screen under the influence of the Leindenfrost effect.The Leidenfrost effect

You’re not having déjà vu.  I already wrote about the Leidenfrost Maze in this blog.  And although physics experiments fascinate many, they don’t normally weigh up as Internet clickbait.  But the Leidenfrost effect is different…

The Leidenfrost effect is a phenomenon in which a droplet of liquid, on a surface which is much hotter than the liquid’s boiling point, will levitate above a cushion of its own vapour.

Although it has been known about for a long time, the complexities that arise due to interactions between three phases of matter far from equilibrium have kept exploratory and investigative efforts from being far from exhaustive or comprehensive.

A diagram explaining how a drop of liquid levitates, and subsequently moves, held up by a layer of water vapour - the Leidenfrost effect.
The physics of the Leidenfrost effect

While this “liquid levitation” was discovered in the 1960s and used in some industries, the fundamental physics of the phenomenon had not been studied until David Quéré and colleagues at École Polytechnique in Palaiseau, France looked into the forces that drive liquid-oxygen drops, which boil at –183 °C, in 2012.

Using simple fridge magnets, they created methods to control the motion of the drops and studied how the drops interact with a magnetic field.  The research followed on from previous studies by the team and others that looked at developing textured surfaces that make the Leidenfrost drops self-propel with a very high velocity in all directions.

Another quirk of the interaction occurs when the drop passes directly above the magnet.  The researchers found that the drop slows down and is nearly trapped by the field.  When it breaks away, the shape of the drop is deformed.  Quéré pointed out that this is interesting in a much wider physical context, because the deformation is caused by a transfer of kinetic energy.

Just like a raindrop hitting the ground, it loses most of its energy as it gets deformed upon impact.

 

The Leidenfrost Maze

A diagram and photograph illustrating the makeshift building of the Leidenfrost maze.
Design and construction of the Leidenfrost Maze  (a) Schematics of the blocks – not to scale. (i) A plain block with a plain surface. (ii) A block with sawtooth surface. (iii) A block with a bowl. (iv) A block with an inclined surface. (b) Photograph of the surface texture being milled. (c) A finished block with a saw-teeth textured surface. (d) The completed Leidenfrost Maze. Source: Cheng et al. 2015

The “Leidenfrost maze” was created by Carmen Cheng and Matthew Guy at the University of Bath to demonstrate the self-propulsion of Leidenfrost droplets at public outreach events and schools.

 

With Added QI

The video created by Carmen Cheng, as part of her undergraduate project, has been available on YouTube since 2013.

The video amassed a whopping 506,676 views.

 

A photograph from the BBC series QI $ ($Series L$ )$ showing Stephen Fry, and the inventor of the Leidenfrost maze, Kei Takashina.
Stephen Fry and Kei Takashina with the Leidenfrost Maze on BBC programme QI

The maze received so much coverage in the international media that it ended up featuring on BBC2’s comedy panel show QI, with host Stephen Fry providing a demonstration of how the maze works.

However, the Leidenfrost maze has recently attracted renewed scientific interest due to a range of factors.

On the one hand, technological advancements such as in high speed imaging, nanotechnology and computational fluid dynamics are enabling its complexities to be examined in new ways.  On the other, developments in microfluidics and heat management call for a deeper understanding of the surrounding phenomena.

 

Visual Feast

A couple of graphs highlighting the number of views of the viral Leidenfrost video.
Instant metrics. (a) Cumulative page views of the paper from the publisher’s website, Scientific Reports, Nature Publishing Group. (b) Daily hit rate of the video hosted on YouTube. Source: Cheng et al. 2015

The novelty of the Leidenfrost maze, its visually striking nature, the sound it makes, the heat that can be felt, the characterful dynamics of the droplets and their controllability all compound to provide a sensory feast, covering visual, auditory and kinaesthetic ‘modal preferences for learning’.

Following the unequivocal success of their maze, the researchers have now published a paper in the European Journal of Physics, published by IOP Publishing, which also publishes physicsworld.com.  The paper discusses not only their experiment, but also mainly the viral nature of the response to their video.

The researchers point out some of the common YouTube comments on the video such as:

“I feel sorry for the poor droplets”

“I can almost hear the droplets go ‘Ouch, ouch, hot, hot, ouch!’ ”

Video viewers even said they found the droplets “cute”.

I had a look recently and I noted a few, rather interesting, spur-of-the-moment comments from the viewers…

“That is jjjuuussssttt cool as balls” !!!
“Yeah, science bitch!”
“Stupid water droplets, quit acting like you’re a lab rat…”
And my favourite one…
“When dropped into the maze all of the little droplets be like “WHEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!!!!!!!”
 
Enthusiastic folks, you will agree.

Not the kind of feedback most physicists are accustomed to receiving.

 

Five Tips

The researchers conclude by listing key ingredients which they feel are essential to the usefulness and enjoyment of their experiences with the Leidenfrost Maze:

  1. Take science that is relatively new.

  2. Let the students choose how it is fun, interesting, stimulating or impressive.

  3. Let the students dictate the aesthetics.

  4. Listen to the press office.

  5. Have fun!

 

And most of all, enjoy watching the video of the water droplets zipping about the maze… and going “WHEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!!!!!!!”  😉