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54 The PCB Design Magazine • November 2016 provided in the manufacturer's data sheet as a guide to ensure optimum performance of their potting/encapsulation process. Health and Safety Resins are generally formulated to be as safe as possible during dispensing and mixing, and certainly safe when cured as part of the end- product. However, with the introduction of the Globally Harmonised System of Classification and Labelling of Chemicals (more succinctly: GHS), many of the hazards pertaining to resins have been re-assessed and resin chemists have been hard at work to develop safer and better performing resin systems. In any event, users should always study the relevant safety data sheets before using any resin product. In gener- al, Part B (the hardener) is more hazardous than Part A (the resin). Good hygiene practice should always be followed, with gloves, eye protection and suitable clothing worn, and good ventila- tion/extraction available in the work area. Well, hopefully the above advice will help get you started as far as resin mixing is concerned. Look out for next month's column, in which I will take a closer look at resin application and tricks of the trade to ensure a smoother applica- tion process and more effective cure. PCBDESIGN Alistair Little is technical director for Electrolube's Resins Division. RESINS: FIVE ESSENTIALS TO ACHIEVE THE RIGHT CURE Reliable, cheap and quick recognition of mol- ecules at challenging con- centrations of ~1 ppb (parts per billion) or less is now possible thanks to a sensor developed at DTU Nanotech. Potential analytes in- clude toxic food additives, chemical warfare agents, hazardous building ma- terials and human disease markers. The sensor consists of nanopillars with heights of 600 – 800 nm. These pillars are able to enhance significantly the spectroscopic fingerprints of the target molecules nearby, making them distinguish- able at ultra-low concentrations. The technique is called surface-enhanced Raman spectroscopy (SERS). Postdoc Kaiyu Wu from DTU Nanotech says that "an ideal sensor for SERS should exhibit re- producibly high enhancement over macroscopic areas and be cost effective. It is extremely difficult to fulfil both." The nanopillar sensor is among the very few throughout the world known to achieve both standards. Just like 'pixels' "Hot spots are the key elements in a SERS sensor, as they resolve the spec- troscopic fingerprints of the target molecules. They are like pixels in a display that resolve different parts of an image. However , hot spots cannot be seen with the naked eye since their dimensions are only sev - eral to tens of nanometers," says Kaiyu Wu. The aim of Kaiyu Wu's PhD project, which fin- ished recently in June 2016, was to engineer "pix- els," i.e., hot spots in the nanopillars in order to take their sensing performance to the next level. This goal was achieved with the help of advanced spectroscopic and theoretical tools, as well as state-of-the-art nanofabrication techniques at DTU Nanotech and DTU Danchip. The nanopillar sensors can be easily paired with portable read-out systems to enable on-site detection of analytes. Furthermore, their high- quality and high-density hot spots guarantee an extra-high sensitivity which reduces the time of detection to just several seconds for regular targets. Nanopillars: A State-of-the-Art Optical Sensor

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