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V magistrskem delu smo zasnovali, eksperimentalno ustvarili in ovrednotili tokovno fokusirane mikro-curke pod vplivom električnega polja. Izvedena je bila analiza tokovnih režimov, oblike Taylorjevega stožca in povprečne hitrosti curka v odvisnosti od variacije volumskega toka uporabljenih tekočin, okoliškega tlaka in jakosti električnega polja. Curek je sestavljala 50 % volumska zmes vode in etanola, fokusirni plin je bil dušik. Za analizo rezultatov je bila razvita programska oprema v okolju Python, temelječa na računalniškem vidu. Z njo je bilo možno samodejno obdelovati zajete eksperimentalne posnetke. Reynoldsovo število za plin in kapljevino je bilo 0 - 190 in 0,09 - 5,4. Negativna elektroda se je nahajala 400 - 500 µm dolvodno od šobe. Pozitivna elektroda je bila potopljena v dovodni kapilari vzorca in izpostavljena enosmerni napetosti 0 - 7 kV. Mikro-curki so imeli premer 1 - 25 µm, dolžino 50 - 500 µm in povprečno hitrost 0,5 - 10 m/s. Ugotovljeno je bilo, da mikro-curki pod vplivom električnega polja pospešujejo po vsej svoji dolžini. To se razlikuje od pospeševanja s fokusirnim plinom, ki je omejeno na območje v grlu šobe. Ta dodatni pospešek, ki je prvič eksperimentalno ovrednoten, odpira možnost razvoja nove generacije zelo hitrih mikro-curkov za dostavo vzorcev v serijski femtosekundni kristalografiji. We designed, experimentally created and evaluated gas-focused micro-jets under the influence of an electric field in this Master thesis. An analysis of the flow regimes of the jet, the shape of the Taylor cone and the average speed of the jet was carried out, depending on the variation of the volume flow of the used liquids, the ambient pressure and the strength of the electric field. The jet liquid was a 50 % volume mixture of water and ethanol, and nitrogen was used for the focusing gas. Software was developed in Python to analyze the results based on computer vision. With it, it was possible to process the captured experimental recordings automatically. Reynolds numbers for gas and liquid were 0 - 190 and 0.09 - 5.4, respectively. The negative electrode was located 400 - 500 µm downstream of the nozzle. The positive electrode was immersed in the sample and exposed to a DC voltage of 0 - 7 kV. The resulting micro-jets had a diameter of 1 - 25 µm, a length of 50 - 500 µm and an average speed of 0.5 - 10 m/s. It was found that micro-jets, under the influence of an electric field, accelerate along their entire length. This differs from acceleration with the focusing gas, which is limited only to a region in the nozzle. This additional acceleration, experimentally evaluated for the first time, opens the possibility of developing a new generation of very fast micro-jets for sample delivery in serial femtosecond crystallography. |
