Capillary Force Fabricates Probes

A team of researchers at Shizuoka University in Hamamatsu, Japan, reports in the March 10 issue of Applied Physics Letters a technique for the fabrication of probes for scattering-type near-field optical microscopes that employs capillary force in micropipettes. The technique is suitable for use with particles of various materials with diameters slightly larger than the inner dimension of the pipette.

To demonstrate the process, the researchers heated and pulled glass tubes into points with diameters of less than 200 nm. Immersed in water with 180-nm-diameter gold particles, the tubes attracted the particles to their tips as the water flowed up the structures by capillary force. Using a CO₂ laser with the fiber puller, they report, enables the fabrication of tips with diameters in the tens of nanometers and the use of correspondingly smaller particles.