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Microfluidic devices have achieved rapid and integrated chemical analysis.However,applications of these devices are limited because they use steady liquid flow and molecular diffusion for chemical processes.In our laboratory,micro droplet collider which uses kinetic energy of an accelerated liquid droplet by colliding with the target has been developed [1].While it achieved enhancement of mixing between two droplets,it could not induce chemical reactions.Though collision velocity in the order of 100 m/s is required for chemical reaction,the velocity of the liquid droplet was limited to 2 m/s due to its breakup by shear force with a microchannel.Therefore,we propose to ice droplet collider using solid-liquid phase transition in a microchannel.It will be able to get enough velocity of ice droplet which does not break up.In this paper,we report on the method of shooting an ice droplet.The concept of ice droplet collider is shown on Fig.1.The ice droplet is controlled by ice adhesion strength on the glass substrate.The accelerated droplet is solidified at -27 ℃ from the supercooling state and stops in the narrow channel (70 μm wide and 30 μm deep) due to large ice adhesion strength.To transport the ice droplet to the launcher part,ice adhesion strength is weaken by warming the cooling part up to 0 oC.At the ice droplet launcher,the ice droplet is detached from the channel wall and shot to the wide channel (90 μm wide and 50 μm deep).At the collision chamber,kinetic energy of the ice droplet converts to collision energy.The shooting of the ice droplet was confirmed because the ice droplet did not change its shape at the ice droplet launcher (Figure 2).The ice droplet which was 70 times faster than the liquid droplet had 4,900 times larger energy at the same condition.Figure 3 shows applied air pressure dependency of velocity of the ice droplet.The experimental data agreed with the theoretical estimation curve which obeyed energy conservation law.From the result,it proved that the ice droplet was efficiently accelerated without energy dispersion with surrounding air.Though the velocity of ice droplet is one order smaller to induce chemical reaction,it will be able to get enough velocity by applying higher pressure.