The liquid-crystal market has undergone revolutionary growth, driven by the manufacture of thin-film transistor liquid-crystal display (TFT-LCD) technologies, [1][2][3] which are fast replacing traditional cathode-ray tube displays owing to their superior efficiency and ergonomics. This growth has lead to increasing demands for displays with improved specifications and ever-increasing complexities. Because a typical liquid crystal (LC) formulation may be a mixture of components; [3] providing the unique desired properties for a specific display or application is complex. Although the formulation and discovery process can use theoretical calculations, iterative formulation and screening of individual compounds is still the order of the day: a time-consuming and inefficient process. Recent developments in high-throughput (HT) materials science, [4] particularly in the areas of ceramics [5][6][7][8][9][10][11][12] and polymers, [13][14][15][16][17][18] have shown that ink-jet printing (IJP) can be used to formulate libraries of two or more components, followed by HT screening to efficiently reveal optimized compositions. In the area of LCs the bottleneck of such an approach was the unavailability of suitable HT analytical techniques. [19] However, this has partially been solved by the development of an optical birefringence method for HT detection of LC phase transitions [20] that constitutes a simple, but important first screen allowing areas of particular interest to be identified and then exemplified using more complex methods such as dielectric anisotropy, optical anisotropy, magnetic susceptibility and viscosity analysis. [21,22] In this Communication we describe the design, optimization, and formulation of a 231 member tertiary library of liquid crystals by using ink-jet printing, followed by screening for phase transitions, with only a few milligrams of material needed for complete library analysis. To create formulation libraries using IJP, a method for the mixing of individual components was required. Literature reports illustrate three methods: mixing of inks behind the inking nozzle, [8,9] mixing of inks before the inking nozzle, [23][24][25][26][27] and mixing of inks on the substrate by dispensing each separate component, in varying volumes, on the top of the previously dispensed component. [18,[28][29][30][31][32] For our application the method of printing on the substrate offered the greatest benefits, as arrays could be quickly produced from small quantities of LC compounds with printing directly onto the analysis substrate without the need for reformatting or mixing. The large surface-to-volume ratio of the printed spots (90 lL) allowed for efficient evaporation of solvent, and sample spotting densities of greater than 30 spots per cm 2 could be achieved. Mixing on substrates has previously been reported by using "small office/home office" ink-jet printers, in which the printing inks were replaced with suitable solutions or suspensions. Such equipment is inexpensive, readily available, and easy to u...

A technique has been developed for the high-throughput ͑HT͒ parallel screening of liquid crystal ͑LC͒ phase transitions, using optical anisotropic effects observed only in the LC state to allow the determination of melting and clearing points. A camera was used to monitor optical changes observed in arrays of LC samples upon heating, when illuminated with plane polarized light and viewed through a second polarizer aligned perpendicular to the plane of polarized light. Data was processed using Image Pro Plus, extracting values for the melting point and clearing point of each sample in the array. When compared with literature and conventional differential scanning calorimetry the new technique was found to be in excellent agreement, establishing the technique as a viable HT alternative. The method was used to analyze a 75 formulation library prepared using liquid handling for HT clearing point determination, showing the scope and power of the technique in the analysis of larger libraries.

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