Liquid Crystal Libraries—Ink‐jet Formulation and High‐Throughput Analysis

Abstract

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...

High throughput methods applied in biomaterial development and discovery

“…An early example was the synthesis of a library of minerals as thin films on a single 'chip' using a sequential masking and unmasking procedure with ion sputtering to produce a range of material compositions [7]. Subsequently, many variations on this theme of combining components to create a range of material types and/or compositions have been published including photoluminescent composite materials [8], polymer films [9], conductive polymers for the creation of electronic circuitry components [10,11], metal salt catalysts [12], transition metal catalysts [13], metal nanoparticles [14,15], ceramics [16][17][18] and organic light emitting diodes [19].…”

In Situ Nanoliter-Scale Polymer Fabrication for Flexible Cell Patterning

“…Recently, this inkjetbased approach was used to prepare 231 formulations of three independent liquid crystals in a HT and highly miniaturized manner (in essence converting a conventional three componentephase diagram into a rectangular format). 35 In addition, it has been used in the preparation of 1800 polymers on a glass slide by in situ nanoliter polymerization. 36,37 Because the already published approaches toward in situ polymerizations were designed for generating large numbers of different polymers in a format suitable for HT cellular screening (microarrays and grids), the recent research has been focused on using in situ polymerization for cellular patterning and enabling an increase in the library of synthetic materials suitable for cell patterning.…”

Gradient and Microfluidic Library Approaches to Polymer Interfaces

“…By varying spin speed and solution concentration, a discrete film thickness library could be built; moreover, the method can be used to cast discrete compositional libraries of, for example, polymer blends. Another route for discrete film library fabrication is ink jetting, which has been explored by several groups [8][9][10][11]. As with sector spin coating, this technique can be used to create compositional spreads.…”