es cells for 15 minutes the effect on cooling rate of capillary dimensions including the inner diameter id and wall thickness wt is shown in fig1 a and 11b for two different wall materials plastics and quartz respectively it is clear from fig1 that the cooling rate increases in a very strong nonlinear fashion with the decrease of the inner diameter for both wall materials especially when the inner diameter is less than 0 4 mm the cooling rate also increases significantly with the decrease of wall thickness and this effect is more apparent when the inner diameter is less than 0 4 mm for both materials these results indicate the importance of micro machined small and thin capillaries for achieving high cooling rate by plunging the capillaries into liquid nitrogen fig1 shows the effect of capillary wall material on cooling rate for two different capillary dimensions id 180 u03bcm and 80 u03bcm with 10 u03bcm wall thickness it is clear that the cooling rate increases when using more conductive material from plastics to quartz fig1 shows a comparison of the cooling rate for the available devices given in table 2 as a function of the boiling heat transfer coefficient between the capillary wall and adjacent liquid nitrogen the cooling rate is almost the same for the two stainless steel and quartz micro capillaries which is about one order of magnitude greater than that of the grid design two orders of magnitude greater than that of the open pulled straw and three orders of magnitude greater than that of the traditional straw it is.