Retro-percussive technique for creating nanoscale holes
A method of forming extremely small pores in glass or a similar substrate, useful, for example, in patch clamp applications, that employs a backer plate to contain energy of a laser-induced ablation through the front surface of the substrate so as to create a rear surface shock wave providing a fire polishing of the exit aperture of the pore such as produces improved sealing with cell membranes.
1. A method of creating nanoscale holes comprising the steps of:
(a) creating a layered structure comprising a substrate material receiving the nanoscale hole and a shock wave containing backer material adjacent to a rear face of the substrate material;
(b) applying a focused laser in a direction of laser transmission and for a first period to a front face of the substrate material to ablate a first crater opening at the front face of the substrate material and extending into the substrate material by an amount less than a thickness of the substrate material;
(c) applying the focused laser in the direction of laser transmission through the front surface and for a second period to heat material beyond the first crater to produce a shock wave generating a second crater starting at the rear face of the substrate material and extending into the substrate material in a direction that opposes the direction of laser transmission and to connect with the first crater thereby creating an opening between the first and second crater having a hole diameter wherein the second crater has a diameter at the rear face larger than the hole diameter.
2. The method of claim 1 wherein in the hole diameter is less than 1000 nm.
3. The method of claim 1 wherein the substrate material is transparent.
4. The method of claim 3 wherein the substrate material is borosilicate glass.
5. The method of claim 1 further including the step of pre-forming pockets in the front face of the substrate material and wherein the first crater is substantially centered within the pockets.
6. The method of claim 1 wherein the material that is heated includes a volatilizable substance.
7. The method of claim 6 wherein the volatilizable substance is a liquid and includes spacers between the substrate material and the backer material defining the thickness of the volatilizable substance.
8. The method of claim 1 wherein the focused laser is applied so that the second crater reaches melting temperatures to create a fire polished surface.
9. The method of claim 1 wherein the laser has a frequency of 192 to 157 nm.