A method of forming a microcapillary structure from a plurality of capillary tubes, comprising the steps of: sealing both ends of the capillary tubes; clamping the tubes together firmly with a holder; placing the clamped capillary tubes into a furnace at a temperature sufficient to soft the tubes to form a stack with the contacting sides fused together and having interstitial spaces between the contacting sides; and heating the stack to a temperature sufficient for drawing, whereby ambient gases from the interstitial spaces is removed to create a pressure difference for causing all contiguous sides of adjacent tubes to close the interstitial spaces and form a uniform microcapillary structure and one end of the microcapillary structure is drawn to reduce its diameter.