Droplet Evaporation Study Applied to DNA Chip Manufacturing

Abstract

DNA chips are potentially powerful technologies for genotyping and gene expression profiling that rely on comparative analyses of up to thousands of "spots of analysis" on a glass support. The spot quality throughout the support influences spot-to-spot variations within an array and the repeatability of data across experiments. For glass slide DNA microarrays, droplets of DNA solution are deposited on functionalized glass slides and left to react through complete evaporation of the droplet. On hydrophobic flat surfaces, different modes of droplet evaporation can be attained. Under atmospheric pressure, water droplets tend to evaporate under two main regimes. Initially, the droplet flattens with a constant contact area, and then the droplet shrinks at a constant contact angle. As a result, the diameter and morphology of thousands of spots on microarrays are not uniform. This leads to poor and unreliable data processing results. In this work, we report the evaporation of an aqueous solution under a constant contact area mode. Evaporation under reduced pressure and the effect of reagent additives to the solution have been investigated. Video microscopy and digital image analysis techniques were applied to monitor the evaporation of the droplets. A mixture of surfactants was developed to maintain a constant area regime during evaporation and to form homogeneous spots. The control of some physicochemical properties (wetting, evaporation rate) of the droplet allows the formation of well-controlled spots compatible with DNA grafting. The influence of surfactant molecules on the mechanisms of evaporation is also discussed.

Instantaneous distribution of fluxes in the course of evaporation of sessile liquid droplets: Computer simulations

“…Let us show that there is inverse proportionality of the local flux to L similar to (2) and the proportionality of the total flux to L similar to (3) remains valid in the general case of an arbitrary contact angle and has nothing to do with flux distribution over the droplet surface.…”

“…Understanding the evaporation of droplets is essential for processes like painting, coating, ink-jet printing, premixing of fuel with oxygen in air [1], particle deposition applications (formation of ring-like spots on the substrate during droplets evaporation), DNA chip manufacturing [2], etc. The measurements of evaporation rate of droplets on different solid surfaces can be used for production of materials providing optimal regime of work in air conditioners, dryers and cooling systems [3].…”

Evaporation of Sessile Water Droplets in Presence of Contact Angle Hysteresis

“…Drying droplets are used in molecular combing process [3,13,32] (e.g. aligning and stretching of DNA molecules); in cooling and heat exchanging systems [31].…”

Dynamics of Drying Process of Polymer Solution Droplets: Analysis of Polymer Transport and Control of Film Profiles

“…[1][2][3] Recently, the drying process of droplets containing nonvolatile materials is focused as an important problem in inkjet printing, which is attracting increasing attention as a key factor in the next-generation fabrication processes for microelectronics [4][5][6] and biomaterials. [7][8][9] A problem that needs to be considered here is the control of the thickness profiles of the solute films deposited on the substrate after the droplets totally dry up.…”