Yale engineers have developed a novel system for producing thin, conductive films. Pictured here, a freestanding carbon nanotube treated with one of the films.
Yale University engineers have
developed a novel automated system for generating strong, flexible, transparent
coatings with promising uses in lithium-ion battery and fuel cell production,
among other applications.
Until now, the slow throughput of some
existing assembly methods has significantly restricted the practical
application of these thin, multilayered conductive films.
Led by André Taylor, an assistant professor
of chemical and environmental engineering, the Yale team developed a new
assembly technique that cuts process time and produces films with both
nanolevel precision and improved function. The system—called spin-spray
layer-by-layer (SSLbL)—generates thin, multilayered films more rapidly than
previously possible and with greater control over film characteristics.
The researchers describe their method in ACS Nano.
“There are many applications for the new
technique in developing functional nanoscale coatings,” says Forrest Gittleson,
a Yale graduate student and member of the research team. “There are [existing] spray-only systems that reduce the assembly time for layer-by-layer films. But
our system improves the process time further while also enhancing the ability
to tune film characteristics. It makes for a powerful level of control.”
In one example cited in the paper, a sample
film was assembled in 54 min using the new method. By contrast, the traditional
assembly method, known as dip-coating (layer-by-layer), took 76 hrs to produce
a film with equivalent conductance.
In addition to improving assembly time, the
new system also offers superior control over the film’s final thickness and
Films containing carbon nanotubes have long
been acknowledged as potentially valuable in sensor and electrode applications.
But it’s been difficult to achieve uniform conductivity throughout the film
using traditional dip methods. The Yale team demonstrates that its method
generates a more uniformly conductive film than the dip method, providing
superior performance potential.
“Because layer-by-layer assembly can be
used with a wide choice of polyelectrolytes and nanomaterials,” says Taylor, “this technique
can be used for an extensive variety of applications ranging from ultra strong
materials (stronger than steel) to transparent O2 diffusion barriers, to drug
delivery. The next application is up to the imagination of the material
researchers assembled ultrathin polymer and nanotube multilayer films, and
evaluated them for use as lithium-ion battery electrodes. The technique shows
promise in developing a better understanding and method for rapidly creating
battery electrodes with nanometer level precision.