15 therein thus the carbon nanotube arrays cnt arrays can be firmly assembled in the space 11 in this embodiment the carbon nanotube arrays cnt arrays 15 include seven carbon nanotube arrays cnt arrays evenly spaced from each other along a horizontal direction and thus eight longitudinal channels 16 are defined therebetween each carbon nanotube array 15 has a shape of elongated cube in which a width w as shown in fig3 thereof is larger than a length l as shown in fig2 thereof the width w of each carbon nanotube array 15 is a little smaller than that of the space 11 and thus two traverse channels 17 are defined by opposite sides i e front and back sides of the space 11 the traverse channels 17 communicate with the longitudinal channels 16 one kind of such a carbon nanotube array 15 can be obtained by a method of chemical vapor deposition cvd firstly aligned carbon nanotube arrays are synthesized in a hot filament plasma enhanced chemical vapor deposition hf pecvd system a substrate metal glass silicon etc is coated with nickel nano particles and then introduced to the cvd chamber then the aligned carbon nanotube arrays are mixed with distilled water by.