Figure 16: A new alloy in the midst of changing phase. The blue needle is the martensite phase,
which is growing into the orange-brown austenite phase as the material cools. In a similar alloy,
one phase is magnetic and the other is non-magnetic, and the resulting material can be used to
turn low-grade heat into electricity. The clean, undistorted interface between the two phases in
this picture is extremely unusual, and in the magnetic version, it creates the near-complete
reversibility of the magnetic field. Credit: R. Delville and D. Schryvers, EMAT, University of
Antwerp, Belgium. Reproduced from the cover of Advanced Functional Materials 12 (20), 2010,
with permission. Copyright 2010, WILEY-VCH Verlag GmbH & Co. KGaA.
Another group is creating membranes that can function inside fuel cellslike artificial versions of the mitochondria that provide energy for biological cells.
The membranes are made of polymer electrolytes, which consist of a
hydrophobic polymer backbone with charges stuck on here and there. These
form a hydrophilic network structure, a bit like a plate of spaghetti – but one that’s
thirsty and sucks up any nearby tomato sauce (or, in this case, water).
When the polymer electrolytes suck up water, the charges push the water into
strange shapes which depend on the stiffness of the backbone and the
placement of the charges. The water could take the shape of a sheet of paper, or
tiny soda straws, or a network of pearls of water connected by pores, or a
fluctuating network of isolated pearls that occasionally meet up. The properties of
the membrane depend on the shape the water takes, and the mathematical
challenge is to predict the behavior of the water from the properties of the
polymer electrolytes.