European-funded project set to deliver blindless panes large enough for new generation of aircraft
A 2m2 (21.5ft2) electrochromic window panel is to be tested this month as the final milestone in an €8 million ($10.5 million) European Fifth Framework project that will ultimately see the technology commercialised for aircraft.
The size of the window, which becomes opaque when a current is applied and would eliminate an aircraft's window blinds, has been a stumbling block for developers. Laboratory prototypes have often been only 20mm2.
Other electronic darkening technologies require a continuous current to keep the pane clear. Suspended particle device (SPD) technology requires the current to be turned off to make the window dark. Electrochromics overcomes this problem by using a technology known as reverse mode polymer dispersal liquid crystal. It is referred to as "reverse mode" because SPD is known as normal mode.
"It has a sponge-like, 20 micron-thick polymer layer that is sandwiched between two sheets of glass, which have an invisible conducting layer of metal sputtered onto their surface. Within the spongey polymer layer is the liquid crystal," says Patrick Crehan, director of Belgium-based consultancy CKA that manages the two-year project.
"The molecules of the liquid crystal are all orientated in one direction when there is no current. This allows light to pass through. When a current is applied the molecules change direction and this scatters the light giving the pane a milky white appearance, "he says.
Crehan's company now has draft license agreements with three companies and is aiming to approach aerospace businesses.
ROB COPPINGER / LONDON
Source: Flight International