The days of having vials of blood drawn for diagnostic testing could become history if lab-on-a-chip technology develops to its full potential. LOCs are a specialised type of micro-electromechanical system device, comprising an array of tiny diagnostic sensors. For example, LOCs may be able to detect early stage cancer cells from a single drop of blood. Other applications include immunoassays, biochemical assays, polymerase chain reactions (used for DNA sequencing) and more. Besides reducing blood-draw-dread, LOCs could be of great service to health care providers in regions that lack medical supplies and lab equipment. However, to realise the advantages of these applications, manufacturing of LOCs needs to be affordable and reproducible. With this in mind, a new approach that uses a glass stamp to replicate patterns on a substrate shows promise as a cost-effective way to make high-resolution patterns, which is a key step in fabricating LOCs. A group at MIT published a paper recently in Nanotechnology, describing the uses of superionic silver metaphosphate glasses to "stamp" precise, nanoscale patterns on silver substrates. Inspired by glassblowers and noting that molten glass can be moulded quickly and smoothly, Nicholas Fang says in a news release with regard to moulding, "It works very well at a small scale, too, at a very high speed." The glass Fang studied, Agl-AgPO3, is a solid electrolyte and has a high room-temperature ionic conductivity, where Ag+ is the mobile ion. Particles of the low-melting composition were melted in a small syringe at less than 200 deg C and pressed onto a metallic master pattern to create a glass stamp. Patterns were stamped by pressing the glass stamp against a silver substrate and applying a voltage above the silver layer. The voltage stimulated ions in the glass and silver surfaces, causing the glass mould pattern to effectively etch into the silver surface. The group reports that patterns in a variety of geometric features were stamped with resolutions of 30 nanometers and etch rates of up to 20 nanometers per second. For more information, the paper is published in full in: Nanotechnology (doi: 10.1088/0957-44/84/22/42/425301), entitled: "Solid-State Superionic Stamping with Silver Iodide-Silver Metaphosphate Glass."
