Library preparation using an aspirating-dispensing ink-jet printer for combinatorial studies in ceramics
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This paper describes an aspirating-dispensing ink-jet printer embedded in a combinatorial robot for high throughput studies in ceramics; LUSI, the London University Search Instrument. The process of reformatting well-plates from source inks and printing ceramic samples is described. Precautions against evaporation, sedimentation of colloidal suspensions, and segregation of mixtures during drying are taken to convert compositions specified in a spreadsheet into the form of ∼1 mm radius drops. It is concluded that when these precautions are taken, commercially available powders can be combinatorially mixed in LUSI to produce samples of 2.4 mg to within 1–3 wt% accuracy.
I. INTRODUCTION
Although combinatorial methods have been widely established throughout medicinal1 and catalyst chemistries,2 progress in materials science has been slower partly because of the prevailing view that prediction of new compositions should emerge from known structure– property relationships. In the area of functional ceramics, there is a view that combinatorial methods have a place particularly in searches for superconductors3 and phosphors.4 Indeed, the formative ideas for automated high throughput screening emerged from Hanak.5 The conventional way of preparing ceramic mixtures involves calculation and weighing of powders followed by milling, drying, calcining, further milling, shape forming, and sintering. In this thick film combinatorial approach, uniformity is based on mixing of low viscosity suspensions containing finely dispersed particles, and the calcining step is excluded. The justification for this is that to achieve stable suspensions, particles must be sufficiently well dispersed not to settle. When mixed, the scale of mixing and hence the diffusion distances for subsequent sintering should be comparable to the particle diameters. Ceramic libraries can be classified as thick film (>20 m) and thin film (
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