Microscopes are the workhorses of countless research labs the world over, performing a wide range of functions, from routine cell culture checks to producing multilayer, high-resolution images of nanoscale specimens. This wealth of applications is facilitated by the sheer array of different microscope platforms available, compounded by the expanding versatility of modern systems. This variety, plus the modular fashion in which microscopes are traditionally supplied, could overwhelm researchers purchasing a new microscope for their lab or core facility; although they can be certain their ideal microscopy setup is out there somewhere, the challenge lies in identifying it. Here we address some of the key features to consider when selecting an imaging solution that will best address your research needs.
Identify your needs
Identifying your needs and anticipating the applications you will carry out using your imaging platform, including any you plan to do further along the line, will make a smoother selection and decision-making process.
Scott Olenych, product manager, who oversees life sciences and academic product marketing at Carl Zeiss Microscopy in the United States, advises: “Get clear in your mind the applications and jobs you need to accomplish [with your imaging setup]. A good sales representative will listen to your needs. For example, if you want to do calcium imaging, they will incorporate those needs into a workflow for you. Having a clearly defined application is your first step.”
Upright or inverted?
Of course, thinking about your intended applications and the samples you wish to view will help you decide right away whether you require an upright or inverted microscope, which either have optics positioned above or below the specimen, respectively. “The other thing to consider is not only the sample itself, but what kind of vessel or holder your sample is going to be in,” says Lauren Alvarenga, associate product manager at Olympus. “This is also important for helping you choose between an upright or an inverted microscope. If your intention is to image in flasks or plastic dishes, you’re going to need a microscope that is both inverted and has objectives with long working distances, to accommodate for the thickness of your vessel.”
An interesting newcomer to the microscopy scene is Echo Laboratories’ Revolve microscope, which eliminates having to choose between upright or inverted. This hybrid platform can switch between the two imaging modes relatively swiftly and easily, and it also frees up room in your lab if you require both types of instrument but are short on space.
Optics
Resolution—the level of detail in which you view something, as well as how fast the image is resolved—is another important consideration.
Objective pieces are critical in this respect, emphasizes Jeff McGinn, president of McCrone Microscopes & Accessories, The McCrone Group’s instrument division: “The higher the numerical aperture (NA) on the objective, the stronger its resolving power. We evaluate the objective NA with our customers based on the amount of detail they want to see, in addition to their budget.” In addition to NA, look at what corrections for spherical and chromatic aberrations the microscope objectives offer.
In terms of any budget limitations, Alvarenga advises: “Choose the best objective lens you can afford. The quality of your objective lens is going to directly impact the quality of your data, so it’s a very important thing to consider.” Then you have objective lenses that are designed for specific techniques, like phase contrast or time-lapse imaging with silicone optics. Phase contrast is typically required in a wet lab environment, especially labs performing cell-counting or viability assays. Also look at working distances (or WD, the space between the lens and the sample), and whether this is compatible with your sample type.
Detection
Another important part of your microscope’s light path is the collection device used to detect the signal from your sample.
“Camera technology is rapidly advancing,” says Olenych, who has seen an increase in the demand for CMOS-based camera chips instead of the more traditional CCD technology. He explains that CMOS chips “are typically larger in dimension than CCD chips and have more sensitivity. They have many more pixels, meaning smaller areas can be imaged in greater detail.” Photomultiplier tubes, or PMTs, are also an option in applications that do not require spatial resolution. Also, because PMTs do not store charge and respond to changes in input light fluxes within a few nanoseconds, they can be used to detect and record extremely fast events.
Usability
Another factor that may affect your decision is the usability of the system. An instrument’s user-friendliness depends largely on its software interface. “Olympus software is pretty universal across all of its systems, and this reduces the amount of time it takes to find your way around a new system or to teach a new person coming into your lab,” says Alvarenga. Several microscope developers have introduced intuitive interfaces that rely on touch-screen technology to control the instrument. For instance, Echo Laboratories’ Revolve is controlled by an iOS application that has a pinch-to-zoom function and can count cells in a single tap. “Usability used to be the lowest [on] the totem pole, but it is becoming more and more important to the user,” explains Eugene Cho, the CEO and founder of Echo Laboratories.
Choosing a vendor
“Choosing a microscope really comes down to choosing the right company,” Olenych counsels. Besides researching the different vendors’ offerings, one of the best ways to distinguish which company to work with is to ask colleagues for recommendations. Remember, you’re forming an ongoing relationship with this company, so it is crucial you find the right one for you.
Michelle Ocana, core facility manager and senior imaging specialist at Harvard Medical School’s Neurobiology Imaging Facility, has a wealth of experience in choosing vendors. Generally, she’ll approach a handful of different vendors. “At least two, but as many as five, depending on the product,” she explains. “I also try to approach a vendor I have never dealt with before, just so that I can take a look at a new product and get to know the accounts manager.” Ocana then invites each sales representative into the department to provide a seminar about the equipment and answer questions from the researchers. “Then I will usually sit down with them, and we’ll have a one-on-one talk to discuss specifics.”
Demos
You should also demo a system with your own samples before making your final choice “so that you can get an idea of how your sample truly interacts with that specific instrument,” Alvarenga says.
“When you get to the demo part of your decision-making process, you should already be okay with the light path and the way the technology is designed,” says Ocana. “What you’re really there to do is evaluate whether the system is stable, in terms of both the hardware and software.” She advises that you demo the platform for several days and push it to its absolute limits: “We usually demo things for a week at a time. For that week, we use the equipment extensively; we’re kind of trying to break it, so we can see where and when it breaks, and how quickly the vendor fixes it.” She explains this is a good indication of how the company and sales rep will go on to support you for the life of the instrument.
Ongoing support
Purchasing a microscope is the first step in a much bigger process. “Once you have a system installed in your lab, it’s important that you learn to care for it so that it continues to perform optimally for years to come,” shares Alvarenga. A lot of reputable manufacturers offer training programs, either on-site at your institution or in their own teaching labs.
Extended warranty programs are also available to help reduce the maintenance costs associated with such a large purchase. But not every instrument requires them. Ocana has this advice: “It really comes down to timing in the end: how long can your system be down? If you need the fastest turnaround to have your system up and running again, then you should carry the warranties.”
The final word
There are a multitude of microscope options and features for scientist to select from. At times, the choices may be overwhelming. The best approach is to do your research, compare instruments, consider your current needs and plan for the future. In the end, as McGinn maintains, “Microscopy is fun science; we love seeing things that we can’t normally see with the naked eye and discovering things we didn’t know were there.”
Image: ShutterStock Images