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Landscapes painted with an electric field

The col­ors on the liq­uid crys­tal dis­play (LCD) can be con­trolled elec­tri­cal­ly, with­out the use of com­plex col­or fil­ters, argue the chemists and physi­cists of the Mil­i­tary Uni­ver­si­ty of Tech­nol­o­gy. It is the only cen­ter in Poland where a spe­cif­ic elec­tro-opti­cal effect is inves­ti­gat­ed. In the future, it may be used in ener­gy-sav­ing TVs or smart win­dows.

On the glass of the smart win­dow, you can dis­play the lagoon or change its col­or to save ener­gy. Such win­dows, as well as LCD with even bet­ter col­ors, obtained in a tech­no­log­i­cal­ly sim­pler way — these are dis­tant, but pos­si­ble appli­ca­tions of the so-called cho­les­ter­ics with an oblique helix.

“The effect of con­trol­ling an oblique heli­coidal struc­ture using an elec­tric field” is inves­ti­gat­ed by Dr. Eng. Mateusz Mrukiewicz. The sci­en­tist brought this knowl­edge from Kent State Uni­ver­si­ty in Ohio and — as the only spe­cial­ist in this field of research in Poland — he devel­ops it at the Fac­ul­ty of New Tech­nolo­gies and Chem­istry of the Mil­i­tary Uni­ver­si­ty of Tech­nol­o­gy.

 “Until ten years ago, mate­r­i­al reflect­ed only light of a giv­en wave­length — that is, only green light, for exam­ple. And if we want­ed red light, we had to heat the mate­r­i­al or chem­i­cal­ly mod­i­fy it. We could­n’t do it imme­di­ate­ly. There were sim­ply no mate­ri­als that would allow to obtain col­ors from ultra­vi­o­let to infrared in a very sim­ple way”- explains Dr. Mateusz Mrukiewicz. Around 2010, a new class of liq­uid crys­tal mate­ri­als with a bend shape — resem­bling bananas — was cre­at­ed. The mix­tures of these mol­e­cules result­ed in a spring struc­ture, pro­fes­sion­al­ly known as an oblique helix. Pre­vi­ous­ly, this spring could not be con­trolled. Today sci­en­tists are able to push and stretch it. By chang­ing the elec­tric field applied to such a mate­r­i­al, it is pos­si­ble to con­trol the col­or of the reflect­ed light In the mate­ri­als pro­duced at the Mil­i­tary Uni­ver­si­ty of Tech­nol­o­gy, researchers con­trol the reflec­tion of light using an elec­tric field. In this way, they obtain a very wide range — from UV radi­a­tion to infrared. New mate­ri­als must switch to dif­fer­ent col­ors as quick­ly as pos­si­ble. For now, this time is too long and strong­ly depends on the tem­per­a­ture. Dr. Mrukiewicz decreased the phase tran­si­tion tem­per­a­ture in the liq­uid crys­tal and select­ed the com­po­si­tion of the mix­ture so that this effect could be obtained at room tem­per­a­ture. Sci­en­tists are on track to over­come this bar­ri­er and sig­nif­i­cant­ly reduce the response time of such a medi­um.

Karoli­na Duszczyk
fot. Mateusz Mrukiewicz