Kwong-Li probes: novel nano-probes for biological dissection and injection

We recently discovered a very fast and reliable single-step etching process to fabricate tiny-angled (<2.7°) fiber probe tips, which is less complex and yields finer tips than other available multiple-step sharp-tip (e.g., SNOM tips) fabrication processes. The process is named as Kwong-Li´s (KL) Method. As the probe profile depends highly on the interfacial meniscus of the etchant, by means of our sacrificial boundary etching technique, in which we introduced glass tubing as etching barriers, probes with very sharp tips and long tapers were formed. Using p-xylene as organic solvent and hydrofluoric acid as etchant, we succeeded in shaping optical fibers (with initial fiber diameter of 125 μm) into sharp tips with angles ranging front <2.7-9.7°, with nanoscale tip diameter of <1 μm. By adjusting the initial etchant height in the tubing, final tip angles can be controlled. With their nanometric tips, these sharp probes will be useful for various scanning probe microscopy applications and could potentially be used as surgical tools for micro cellular surgery, i.e., we have already shown that KL probes will penetrate through cell membranes with less mechanical resistance than conventional pipettes and probes made by Turner´s Method. The fabrication process of KL probes and experimental results from using KL probes to probe cells are presented in this paper.