Desktop EM - here to stay for good?
I recently attended the Big Bang Fair with my children at the NEC in Birmingham. For those of you who don't know, the Big Bang fair is a science and engineering event aimed at children aged 7-19 and allows them to interact with professionals from a range of disciplines including medicine, food science, robotics, aerospace and the physical sciences. There are also live shows full of explosions and engaging displays presented by enthusiastic presenters. At a number of the stands there were microscopes where children could look at their own cheek cells or prepared specimens. One of the stands related to the Mary Rose had a very large flat screen TV, which I quickly identified was connected to a desktop SEM. I'm pretty sure there will have been many children and adults who would have initially mistaken the microscope for an oversized desktop PC. Naturally I became rather excited at seeing this, however, we were short of time and trying our best to see all the stands before leaving so couldn’t spend time there. Although I didn't get to investigate further, it left me wondering about these miniature microscopes that seem to have come onto the scene a few years back and seem to have stuck around.
Many kids have the opportunity to use a light microscope, and there is actually a RMS initiative to bring light microscopy kits to schools in the UK. I’m pretty sure that most kids would jump at the chance to get even closer to a sample by using an electron microscope and from what I can see that’s exactly what desktop SEMs allow at a reasonable price. What they represent is the chance for ordinary people to see what many of us take for granted on a daily basis, but the cost isn’t really what I’m focusing on here, rather their portability. For shows (such as Bigbang) and the manufacturers who make the microscopes, they are a very straightforward, effective solution to facilitate an understanding of electron microscopy and its power to inform and inspire us by enabling the visualisation of structure. But it doesn’t have to stop with school children and parents, these instruments are ideal for undergraduate students in a wide range of disciplines, particularly in departments who don’t have the resources, space or personnel to host a microscopy lab, but who recognise that exposure to SEM is important to the students.
It also doesn’t have to be used merely as a plaything or demonstration piece, rather the low cost and ease of use is a selling point to PhD or postdoc users, who require some serious analysis and images but who want a more push-button experience, with fewer options and less training, or company users who don’t want to run a full lab. ‘This is all fine in principle,’ I hear you say, but what magnifications are available on these machines compared to their big brothers and will it have my normal analysis tools??
Well before you assume that they can’t be configured to run EDS, capture BSE images or run a cooled stage, let’s look at what the options are. As far as I can see there are four main options in terms of manufacturers. PhenomWorld is a company that formed to sell the Phenom desktop SEM, which was previously marketed by FEI. There are three variations of the microscope: the Pro (high brightness, mid-range), the ProX (top of the range, including with elemental analysis) and the Pure (entry level). The advertised magnification is between 20x and 20,000x (pure) and 100,000x (ProX) with a choice of accelerating voltages (5- 10 kV pure/Pro and 5-15 kV for the ProX). There seem to be a range of holders available and software packages to support the machines and specialist applications.
The Phenom G2 Pure and Pro, represent two of the three flavours of Phenom, courtesy of FEI.
The next option is from Hitachi in the form of the HT3030, who offer their most recent desktop after launching the TM1000 in 2005. After reading the descriptions on the website, the unit is pitched as a simple solution for everyone to use for high quality imaging at either 5 kV or 15 kV performed at low vacuum to minimise the need for coating. EDS is an option as is a charge reduction option to reduce drift.
The Hitachi TM3030, courtesy of Hitachi
Next, we come to the Neoscope from JEOL. The latest version of the JCM-6000, (which comes with three accelerating voltages) can be operated in either high or low vacuum mode, and comes with EDS. As with many of their recent microscopes the unit is touchscreen, to facilitate more straightforward interaction with the microscope, yet again making it easier to embrace electron microscopy.
The JEOL Neoscope offers touchscreen technology, courtesy of JEOL
When researching this article, the last manufacturer I came across is Hirox, who aren’t one of the big four main manufacturers, but offer a refreshing change in the four variations of desktop SEM, which appear to have the full typical range 5-30 kV and magnifications 30k – 100k. Again we see the familiar options of high and low vacuum offering support for non-coated samples as noted for the previous manufacturers, with one of the units offering a 5-axis stage. Options for detectors include EDS, BSE and SEI detectors and a cooling stage for sample that require special handling conditions.
As I was concluding this blog, I searched for further information and websites that may have explored these instruments, their advantages or disadvantages and general reaction to them by microscopy professionals. I came across a few interesting forums including one on LinkedIn and websites touting desktop microscopes. One of the most intriguing was the LV-EM.com website by Delong America, who market the only low-voltage combination instrument, called the LVEM5. This desktop is not just a desktop SEM, but rather a transmission EM, scanning EM, scanning transmission EM and electron diffraction instrument.
The impressively small, but versatile LVEM5, courtesy of LVEM
The low accelerating voltage and flexibility of imaging mode at the same small footprint instrument is intriguing. From the marketing, it is clear that the appeal is the multi-imaging that the LVEM5 offers combined with the good contrast that low kV imaging brings with it for TEM. As with all the desktop EMs, the simple to use ethos makes it good for teaching and relatively low price compared with standard TEMs definitely deserves a closer look.
All things considered, these little EMs open things up from what some may have originally seen a fancy image taker to a more serious analysis tool. They clearly have the advantage that they can be ported around a factory, between sites in a department or into the field where the power to image something at 10,000x may be enough, even if the sample is studied further on a standard SEM later. I am aware that on this brief blog on the subject I have merely offered up some of the options as I am aware of them and have in no way fully explored the pros and cons at length. Nor have I investigated prices, maintenance issues or the idiosyncrasies of the various instruments. Due to brevity, I haven’t covered how these instruments have been used for academic publishing, but I know that papers have been published using them.
I’m sure you’ll all have comments on this topic and I’d love to hear them, so please get in touch!