fantastic plastic

Instead of the usual rubbed polyimide alignment layers,

they use the in-situ photopolymerization of alkyl acrylate monomers in the presence of nematic liquid crystals to provide a cellular matrix of liquid crystalline droplets in which the chemical structure of the encapsulating polymer controls the liquid crystal alignment.

“Small changes in the chemical nature of the polymer will change the alignment of the molecules at surfaces,” said Mohan Srinivasarao, a professor in Georgia Tech’s School of Polymer, Textile and Fiber Engineering. “It turns out that this can be done over a fairly large area, and it is reproducible.[…]”

Srinivasarao described the self-aligning of liquid crystals Sept 14 at the 232nd national meeting of the American Chemical Society in San Francisco.

Apart from eliminating the rubbing step (a potential yield killer) the technique offers the following advantages over standard standard LCs for Ds:

• resulting displays are less sensitive to mechanical deformations (rigidity provided by the liquid crystals), and thus more suitable for flexible displays

• completely dark ‘off’ state (made possible by the vertical alignment of the liquid crystals)

Srinivasarao and collaborators Jung Ok Park and Jian Zhou have used the technique and a nematic material with negative dielectric anisotropy to fabricate highly flexible liquid crystal devices that have high contrast and fast response times – without using an alignment layer. Control is obtained by variation of the alkyl side chains and through copolymerization of two dissimilar monofunctional acrylates.

Bi-stable metal sheets might be useful as substrates for rollable screens (e.g. electronic newspaper). The ‘dimpled’ copper-alloy structures are apparently cheap to produce from a single sheet of metal.
BBC article
Smart structures group at the Department of Engineering (Cambridge)

George Malliaras and coworkers at Cornell created a novel type of organic diode with an “ionic junction” by laminating together layers of

an anthracene derivative containing free positive ions and a ruthenium, complex containing negative ions. When the two are joined, ions diffuse across the junction creating a difference in energy levels that facilitates rectification, electroluminiscence and photovoltaic response.

The technique is potentially suitable for low-cost fabrication of flexible photovoltaics and LEDs.

The work is described in the Sept. 7 issue of the journal Science in a paper by Cornell graduate researchers Daniel Bernards and Samuel Flores-Torres, Héctor Abruña, the E. M. Chamot Professor of Chemistry and Chemical Biology at Cornell, and Malliaras.