High density energy storage using self assembled materials
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precision was a hallmark of space
exploration in the 20th century precise orbits precise take-offs precise landings now in the 21st century a new kind of
precision has enabled an exploration of a fundamentally different kind the through the phenomenon of self-assembly we can now design materials with atomic
precision materials that may revolutionize practically every
technology on earth: for example the fuel tank the problem
with fuel tanks today is that they can only store liquid fuels
such as gasoline also called petrol gaseous fuels like
methane are much better for the environment but
because gas molecules tend to spread out as far as they can an ordinary fuel tank would contain very
little fuel at standard pressure a tank of methane contains a little over
1000th the energy of a tank of gasoline enough to drive about 100 meters if you
were to look closely at the walls of the fuel tank containing methane you would notice the molecules are much
less spread out this is because methane like all gases is attracted to surfaces
this suggests a simple improvement to our tank design simply extend the walls of the tank inward to increase the surface area the freshly exposed surface will attract
new methane molecules which in turn will allow us to store more
methane in our tank than before we can visualize the total amount of
methane stored on the inner surface of our tank by laying out each molecule on an
imaginary flat surface with our creative while extension idea a
fifty liter or 12 gallon tank would have one square
meter of methane stored on the surface not bad but perhaps we can do better a
simpler more effective idea is to simply fill our tank with sand
each grain of sand adds a small amount of surface area but millions of grains of sand can fit
inside the tank this simple strategy results in 100
square meters of internal surface area and a significant increase in the amount
of stored methane consider the self assembled crystal NU100 designed at
Northwestern University by Farha and colleagues unlike sand each crystal contains
trillions of identical pores that allow methane to get inside this
multiplies the surface available for methane storage filled with NU100 crystals
we obtain a total surface of 50 million square meters but do even better materials exist to
find a better material let’s examine NU100 it is
self assembled from an organic chemical and metal copper atoms which is why it’s
called a metal-organic framework there are many organic chemicals and
many metals for the small number of chemicals we are showing here they’re already nine thousand possible
materials which is the best one it would take a chemist many years to
try all these reactions thankfully we don’t actually have to
make every material to find the best one we can computationally simulate them
the enormous complexity of simulating methane gas interacting with trillions of
self-assembled molecules can be reduced to the problem of simulating the smallest repeating
element we can predict how well a crystal
stores methane by connecting it to an imaginary methane reservoir we then fill the crystal with methane
until the system has reached thermodynamic equilibrium once equilibrium is reached we generate thousands at random
configurations of methane molecules each of which contributes to a
statistical average of overall methane storage this is just one possible material using
supercomputers we can simulate hundreds of thousands of
materials simultaneously each material is generated by computer
algorithms developed by Wilmer and peers and then simulated to obtain physical
properties essentially performing millions of computational experiments
in the time a chemist needs to create just one material the best materials of the hundreds of thousands
are identified by the supercomputer and it is left us to create them in a lab we will rely on
self-assembly so that we create these materials
precisely with every atom in its place

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