The scientific facts behind the Dr Who sonic screwdriver are even more exciting than the fiction

Doctor Who uses his fictional sonic screwdriver in a wide range of situations this includes opening locks, breaking into computers and cash machines, defusing bombs in addition to rotating screws. However, research suggests that this iconic sci-fi device is at least partly based on scientific facts.

The idea that sound waves carry energy seems intuitively reasonable – think about the physical sensation we humans get when we approach powerful speakers with heavy subwoofers found at concerts and clubs. . Sound can be felt physically and not just heard. A fantastic demonstration of this phenomenon can be found in acoustic levitation experiments: If the distance between a speaker and a reflector is adjusted so that a standing wave forms, objects can be lifted and held aloft in regions of low pressure called knots.

While this sounds like a frightening action from a distance, it’s purely because acoustic waves, like their electromagnetic counterparts, carry momentum. This means that they can apply a force, usually called acoustic radiation force. If the force is stronger than gravity, objects can be levitating. Speakers typically produce a linear pulse, so they can push objects in a straight line.

This can be of great help to fend off the daleks, but no need to turn the screws. This is where acoustic vortices come to the rescue: They are acoustic waves with spiral-shaped wave fronts, called a helix (like a strand of the DNA double helix). This spiral pattern provides acoustic vortices with a rotational rather than linear amount of motion. If that momentum can be transferred to an object – like a screw – the result is a sonic screwdriver.

The first to come close to a true sonic screwdriver was a research team from the University of Dundee who in 2012 created a acoustic vortex with a special medical ultrasound transducer designed to destroy tumors. They used this device to spin a large disc made of a material that absorbed the spinning momentum of the waves. It was impressive, but it didn’t replicate much of the capabilities of the Sonic Screwdriver. We went further by showing that similar devices can be reduced and used to manipulate microscopic particles.

We created the required swirling sound waves using a number of tiny ultrasonic speakers arranged in a circle. This device, only 10 mm in diameter, created acoustic vortices of about 1 mm. In turn, these tiny acoustic vortices were capable of spinning objects measuring between one and 100 microns – roughly the width of a human hair. If the objects were sized right, the acoustic vortex would act like a tiny tornado.

Acoustic vortices, seen in experiment (top) and theoretical predictions (bottom), showing how mm-scale acoustic vortices spin 0.5 micron tracer particles. The color indicates the rotational energy of the vortex.
Bruce Drinkwater / University of Bristol, Author provided

For example, when a mixture of household flour and water was placed in the apparatus, the flour particles were sucked into the core of the vortex where they rotated at high speed. Conversely, the smaller particles moved slowly in circles and were not at all attracted to the core of the vortex. This millimeter scale means that we now have what could be called a sonic watchmaker’s screwdriver, potentially capable of loosening the smallest screws.

So while it’s great to anchor the imagination of Doctor Who writers in the science of sound, do these acoustic whirlpools have any use in the real world? The answer is yes, but maybe not in the way that Doctor Who might imagine. For example, they could be used to create microscopic centrifuges to sort biological cells or to purify water. What makes this possible is that this latest study showed how particles of different sizes behave differently when exposed to tiny acoustic vortices.

Now with more sounds and more nanoparticles.
krupptastic, CC BY

More exciting is the knowledge that the motion of particles is also extremely sensitive to their material properties, such as stiffness and density. This could lead to new methods of medical diagnosis. If, for example, healthy cells can be distinguished from unhealthy cells (cancer cells are considered softer than healthy cells), these detections could be possible on a very small scale – perfect for medical diagnostics and forensics.

It is likely that acoustic vortices will soon join existing methods as a new tool for the controlled manipulation of tiny and microscopic matter. So sometimes science facts are just as interesting as science fiction – now if someone could just reverse engineer the TARDIS.

Source link

About Donald P. Hooten

Check Also

Dogs Reveal Scientific Facts With Their Own “Pawdcast”

Bunsen the Bernese and a retriever named BEAKER are the not-so-secret ingredients of a social …

Leave a Reply

Your email address will not be published.