"Man-made materials" make most people think of disastrous fashion, or whine about how things were better when everything was natural and green, and infant mortality wasn't just a worldwide fact but an accurate ratio.
The only context in which this is a better choice of picture.
Mother Nature exposes us to bear attacks and the hantavirus. That's the sort of mother-something Samuel L. Jackson gets upset about. It's also why we invented doors and electrical supplies to keep her out, and have been building incredible unnatural things ever since.
Antimatter is the most science-fiction-sounding substance in existence, which is weird, because it is in existence. And has been science-fact for over 80 years. Antimatter particles were predicted (by Paul Dirac) and dectected (by Carl D. Anderson) before World War II (and any authors looking for an alternate history novel idea, you're welcome). It's so well understood that we now watch it annihilating bits of sick people to understand what's wrong with them. Positron emission topography doesn't annihilate the sick bits directly, but it's important that you understand that this sentence ends in yet.
Lawrence Berkeley National Laboratory
We inject patients with radioactive material and feed them to the Science Doughnut to track the gamma radiation, and maybe create an Avenger.
When antiparticles meet their match in our universe, it's even more spectacular than when Jet Li does it. Both are annihilated, converted entirely into high energy blasts that can punch through almost anything. (Also like when Jet Li does it.) Note that even scientists, who refer to earthquakes and tidal waves as "events," use the verb "annihilate." Antimatter science makes Daleks sound understated.
EX-CUUUUZE ME, WE FIND SY-NAJ LESS GRAY-TING THAN OUR VOY-SEZ!
So what did science do with the kamikazes of particle physics? Played quantum Lego! They took the self-destruct switches of the Standard Model and built bigger things out of them. Early experiments at CERN created antihydrogen -- the first full anti-atom -- over 15 years ago, but because the antimatter was created at almost the speed of light, it exploded things far too fast to study. Notice how even science's problems sound more awesome than every other field's successes.
Curses, we accidentally demonstrated our mastery of mass-energy conversion. Again.
The problem is that artificially creating antimatter requires ludicrously energetic high temperature collisions, but convincing them to join together means keeping them cool. Luckily, science translates "the problem" as "that thing we haven't done yet." Modern experiments hold the antiparticles in magnetic fields, the smartest possible version of "Not touching you, can't ex-plode!" In 2010, CERN's ALPHA experiment trapped antihydrogen, the opposite of most of our universe, for a sixth of a second. A year later they held it for a quarter of an hour. Understand: Scientists can hold impossible materials together longer than most Internet users can hold their own attention spans. Think about that the next time you read online "debates" about vaccinations or evolution.
A universe entirely made of antimatter wouldn't be a Michael Bay reality show. It wouldn't explode, we wouldn't have goatee beards and the Nazis would still have lost World War II. Antimatter can't explode without matter to set it off. Whether we're made of one or the other doesn't really matter, it just multiplies it by minus one. Positronium doesn't suffer this problem. In fact, positronium doesn't suffer any problems, or solutions, or anything at all for longer than one six-millionth of a second, because it's a real atom that is half matter, half antimatter, all awesome. We never thought we'd say this, RoboCop, but you've been out-hybrided.
In contrast, the Prius was an easy victory.
In boring atoms, negative electrons are attracted to and orbit a positive nucleus. In positronium, the negative electron is drawn to an anti-electron, the positive positron, the most awesome tautology ever to exist. This substance makes moth and flame look like a diamond anniversary relationship. The particle-antiparticle pair have a full atomic structure, energy levels, the works, before annihilating each other. It's the lightest element in existence and so amazing that even Star Trek hasn't used it. Commander Data is the smartest character from that show, and his brain can only hold half of this stuff.
He sees what I did there.
What do you do with an existence-taunting atomic self-destruct system? You make it bigger! Scientists at the University of California Positron Lab said "Atoms? Psssh, we can mock the concept of mass itself with molecules!" They fired positron beams into porous silicon targets, trapping positronium atoms to create full positronium molecules. Note how what they just did for real is more awesome than what most people do in video games, movies or their wildest drug-fueled dreams.
The University of California Positron Lab, which is a thing that exists and is awesome.
And it looks even more like mad scientist equipment than we hoped!
Someone with no soul, brain or right to call themselves part of a tool-using species might ask what's the point of achieving these impossible materials. Luckily, Professor Mills and Dr. Cassidy have an answer, and that answer is the positronium annihilation gamma ray laser. You will never hear a better answer to anything. "Annihilation" isn't its function, but its mode of operation. That's a real scientific paper that honestly kicks the shit out of schematics for the Death Star. True, the technical challenges to be overcome read like CERN's letter to Santatron from the year 3000, but one of the requirements was molecular positronium, and you didn't even know why that was impossible two paragraphs ago, never mind that they'd already done it. When it works, it'll be able to investigate the fine-structure constant of the entire universe with unprecedented accuracy. Possibly because the universe will be too terrified to keep secrets.
Human history is a timeline of improving on nature. First our bodies sucked, so we started picking things up instead of waiting to grow them. Then those things sucked, so we crafted them. Then the materials they could be made from sucked, so we made new ones like bronze and steel by alloying elements. Then we were limited to materials that can be made from elements that exist -- so we're making new ones that can't.
We've already built people who shouldn't naturally exist.
Metamaterials overwrite the laws of atomic physics with larger-scale versions. By building repeating structures on a small enough scale, incoming light sees those structures instead of the atoms they're made of, so you replace molecular properties with designed ones. These are intelligence alloys, materials improved by mixing them with intelligence instead of impurities. The most interesting property so far is negative refractive index, and since most people don't deal with refractive indices, asking for a negative one is like demanding a pegasus's aerodynamics or a yeti's boiling point. Even asking for it implies that you didn't understand what some of the words meant.
Unfortunately for unicorns, the Internet would later understand apply both meanings of the word "horny."
The refractive index controls the behavior of light in a material, and in nature they're all positive and greater than one. Negative indices were impossible right up until we built them. They were impossible in the same way a negative number's square roots were impossible: nonsensical until we worked out how to do it, when it became vital in hundreds of amazing new applications we'd never have expected. We're already using these negative index materials in electromagnetic cloaking experiments and superlenses that can beat the natural diffraction limit. They have possible applications in lithography of computer circuitry, nanotech, antennae, trapped light technology and potentially pretty much every application that uses light or electromagnetism. Which is all of them.