Insect-inspired microfluidics could help Ant Man and the wasp to breathe

The ability to quickly reduce the size of bugs (and beyond) gives Ant-Man and Wasp tremendous benefits. But there are also disadvantages of scale, including more difficult breathing. Prepare your costumes with small insect-inspired air pumps, compressors, and small molecule filters, combined with the fictional "Pym particle" technology, There you go! Problem solved.

Anne Staples, a Virginia Tech engineering engineer, and her graduate student, Max Mikel-Stites, first described the breathing difficulties that Ant-Man and the Wasp would likely face when they were the size of an insect in an article published this summer in the nascent newspaper. Science and technology of superheroes. (Can I just say how pleased I am that this diary exists?) The group is studying microscopic breathing using insects as models. They described their work at a meeting of the Fluid Dynamics Division of the American Physical Society in Atlanta, Georgia.

Mikel-Stites, a fan of the Marvel film universe, was delighted to Ant and the waspthe Liberation. So, one day working at the lab last spring, the conversation naturally focused on the difficulty breathing for superheroes at the size of an insect. "Applying this perspective to Ant-Man and the Wasp seemed like a simple thing to do," says Mikel-Stites, who admits to being a bit fussy about science in movies. And he could not help thinking about the breathing problems that our superheroes would inevitably face.

The smaller the animal, the less effective its metabolism is, according to Kleiber's Law (named after biologist Max Kleiber). This is probably because the surface area / volume ratio increases as objects become smaller. "Animals produce heat in amounts proportional to the volume of their body, but dissipate it in amounts proportional to the surface of their body," says Staples. "Thus, small animals, which have a high surface area to volume ratio, dissipate heat at a high rate and can not stay warm." To compensate for the heat loss, they need a higher metabolic rate. Small animals therefore produce more heat and need more oxygen than larger ones.

Certainly, Marvel movies do not clearly indicate if the mass of Ant-Man also decreases when it shrinks. "Sometimes it seems like he's got the mass of a human – he falls and cracks a tile – and sometimes he seems to have the mass of an ant [when] he runs on the barrel of a rifle and rides on Ant-thony, his ant friend, "Staples says.

"The subjective atmospheric density experienced by a human who reduces to the size of the insect changes."

They decided to assume that the masses of Ant-Man and Wasp were reduced by eight orders of magnitude when they were reduced to the size of an insect. This means that their total metabolic rate would be reduced by only six orders of magnitude. This translates into a mass per unit 100 times that of superheroes when they are human-sized. They would need 100 times more oxygen to function.

"While the actual atmospheric density is the same for an insect and a human, the subjective atmospheric density experienced by a human is reduced to insect-size changes," Mikel-Stites said. When Scott Lang breathes to his normal size, he breathes a number of oxygen molecules. Reduce yourself to the size of an ant, however, and it still needs the same number of oxygen molecules, but accumulates much less with each breath.

This is equivalent to that mountaineers on Mt. Experience Everest in the famous "death zone" of the summit at 7998 meters altitude. Most people respond to these conditions by breathing more quickly and bringing more oxygen, if only to avoid headaches and vertigo associated with altitude sickness.

Fortunately, microfluidic devices – the kind that Staples and his group are developing – could help. Insects and humans have developed very different breathing strategies because of the great diversity of life scales. According to Staples, many insects collapse their tracheal lanes when they breathe. There are not two insects that act in exactly the same way, but it usually takes abdominal contractions to trigger the collapse. "Sometimes the collapses spread along the tracheal lanes during a wave of contraction, and sometimes they occur at different places along the same tracheal tract," she says.

The equipment of the Virginia Tech team mimic different combinations of these three main features of insect respiration. By exploiting these strategies, the group has managed to build four (so far) tiny insect-inspired lab-on-chip machines that allow them to control small-scale fluids with great precision, without the need for bulky valves. An article on this work is pending publication and Staples' colleague Krishnashis Chatterjee described some preliminary results of the conference.

So how could microfluidics help our superhero friends breathe at smaller scales? To compensate for the insufficient suction force to draw air into the helmet mask, it would be possible to pump the air with a pump called "Knudsen pump". It depends on temperature differences to pump gases (such as air) through pores at the nanoscale in many minerals. There would certainly be a temperature difference inside and outside the Ant-Man and Wasp combinations.

Then, a way should be found to compress the air supply to obtain equivalent oxygen molecule densities at sea level (as opposed to the high altitude death zone of Everest). This assumes that the man and the wasp retain their human masses. "Compressing the air would allow them to get the same number of oxygen molecules in a lung of air," says Staples. "There are a number of microscale compression technologies, such as microscale diaphragm compressors, that can be operated mechanically or electrostatically."

Finally, the addition of a molecular filter (such as an H filter) could also help superheroes cope with the increased demand for oxygen. Such a filter would remove molecules smaller than oxygen from the air, thus increasing the relative oxygen content, exploiting the different diffusion time scales for molecules of different sizes. Combine these three particles with particles of Pym – supposed to allow a reduction or expansion of the distance between atoms and matter, as well as the manipulation of mass – and you get a viable solution to the problem of breathing.

The Staples group debated the type of superheroes they should choose for their next incursion into comics physics. Always a fan of Marvel, Mikel-Stites pushed Dazzler, who possesses sonoluminescent powers (think of the sonic shock wave produced by the powerful slamming of a mantis shrimp claw, in the broad sense). Afreen Khoja (and DC Comics), another graduate student, won: they will study the hydrokinetic powers of Mera, Aquamanis the princess of Atlantis.

DO I: Science and technology of superheroes, 2018. 10.24413 / sst.2018.1.2474 (About DOIs).