Cite this: Lab Chip, 2013, 13, 156 Rapid fabrication and piezoelectric tuning of micro- and nanopores in single crystal quartz Received 14th August 2012, Accepted 22nd October 2012 DOI: 10.1039/c2lc40925a www.rsc.org/loc Eric Stava,3* ab Minrui Yu,3 a Hyun Cheol Shin, c Hyuncheol Shin, a Dustin J. Kreft a and Robert H. Blick ac We outline the fabrication of piezoelectric through-pores in crystalline quartz using a rapid micromachining process, and demonstrate piezoelectric deformation of the pore. The single-step fabrication technique combines ultraviolet (UV) laser irradiation with a thin layer of absorbing liquid in contact with the UV-transparent quartz chip. The effects of different liquid media are shown. We demonstrate that small exit pores, with diameters nearing the 193 nm laser wavelength and with a smooth periphery, can be achieved in 350 mm thick quartz wafers. Special crater features centring on the exit pores are also fabricated, and the depth of these craters are tuned. Moreover, by applying a voltage bias across the thickness of this piezoelectric wafer, we controllably contract and expand the pore diameter. We also provide a sample application of this device by piezoelectrically actuating alamethicin ion channels suspended over the deformable pore. Introduction Decades of research have led to many different applications for micro- and nano-sized through-pores. 1–3 The novelty of these small pores lies in their function as a critical interface between larger, fluidic chambers, where they may act as colloidal filters, 4 thin-film supports, 5 planar patch-clamp substrates, 6 or molecular detectors. 7–10 The application of each device is determined by the pore’s size, shape, substrate material, and surface properties. A superior pore, therefore, is one with controllable size, shape, and material properties. While there is vast literature devoted to controlling through- pore surface properties, 11–14 few studies have demonstrated precise control over the geometry of the pores themselves. 15,16 In particular, a piezoelectric pore would introduce real-time control over the pore geometry, greatly enhancing its applica- tion. In this paper, we show the capability of rapidly fabricating and piezoelectrically tuning submicron through- pores in single crystal quartz. When fabricating micro- and nanopore devices, proper selection of the substrate material determines the device’s functionality and resultant resolution. For most applications, a dielectric, biocompatible, optically transparent material is ideal. Materials such as polydimethylsiloxane (PDMS), 17 borosilicate glass, 18 and fused quartz 6,19 have all been used. Crystalline quartz, however, is a superior material: it exhibits great structural stability; 20 it has good thermal and chemical stability; 21 it yields excellent optical transmission over a large spectrum, from UV to infrared; 22 and the dielectric properties of single crystal quartz (dielectric constant y3.8; dielectric loss factor y10 24 ) make it a high-quality electrical insulator. 23 The superior insulating properties of quartz are particularly crucial when utilizing nanopores for electrical measure- ments, 24–26 as they allow for reduced dielectric and RC-noise across the substrate. 23 Also, much like glass, quartz is compatible with biological materials. It is the material of choice in ion channel screenings, 27 where it can act as the support for planar lipid bilayers, 28 the pipette in traditional patch clamping, 29 or the microstructured substrate in planar patch clamping. 15 Further, the piezoelectric characteristics of single crystal quartz allow for precisely-tunable pore dimen- sions. This unique attribute provides single crystal quartz pores with a wide range of applications, especially in the field of mechanosensitive ion channels. Desirable fabrication techniques of micro- and nano-sized pores are those which rapidly produce pores while maintain- ing precise control over their sizes, shapes, and locations. Traditionally, microfabrication of quartz is performed via a combination of lithography and reactive ion etching. 30 However, this approach involves multiple steps, yielding slow turnover and, with each additional processing step, proclivity for error. A more direct microfabrication technique is laser ablation. 31,32 This technique typically uses a high power a Department of Electrical and Computer Engineering, University of Wisconsin- Madison, 1415 Engineering Drive, Madison, WI 53706, USA. E-mail: estava@wisc.edu b Institut fu ¨r Angewandte Physik und Zentrum fu ¨r Mikrostrukturforschung, Universita¨t Hamburg, Jungiusstraße 11, 20355 Hamburg, Germany. Fax: +49 40-428-38-6332; Tel: +49 40-42838-2910 c Materials Science Program, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA 3 These authors contributed equally. Lab on a Chip PAPER 156 | Lab Chip, 2013, 13, 156–160 This journal is ß The Royal Society of Chemistry 2013 Downloaded on 04 December 2012 Published on 24 October 2012 on http://pubs.rsc.org | doi:10.1039/C2LC40925A View Article Online View Journal | View Issue