i-doT - A New Immediate Drop on Demand Technology for High Flexible and Automated Liquid Handling

Introduction of microarray technologies in bio-sciences initiated a revolution unparalleled by any other development in this field of research. Yet there is one obvious problem with existing spotting technologies: to avoid cross contamination among different spotting fluids, the dispensing unit has to be changed or cleaned after each spotting process. The underlying idea of i-doT is to allow direct sampling through micro drill holes at the bottom of a well plate. Capillary pressure in the micro hole is higher than the pressure of the water column above, thereby preventing any leakage of the sample. By applying a short pressure pulse onto a well a small amount of liquid separates at the well's nozzle. In an experimental setup very small droplets with volumes of about one nanoliter were printed. By applying a pressure pulse of 10 to 15 psi for a duration of 500 ns to 1 ms, using nozzle diameters of 50 to 125 µm, spot diameters between 150 and 200 µm were achieved. Therefore this system is capable of printing up to 20.000 spots of up to 384 different samples onto one glass slide (25 x 75 mm). Depending on the mechanism of the printhead up to 15.000 Spots per hour are possible. The presentation will illustrate underlying innovations as well as technological developments leading to the immediate drop on demand technology. Furthermore it will discuss trends and future applications for high throughput microarray applications.