Wednesday, July 1, 2015

This is Not a Microscope

This is not a microscope. This is only an image of a microscope, an image of a lens-free microscope to be exact. This is the first you’ve heard of a lens-free microscope? Well, the technology has been around since the 1950s, although they used mercury lamps instead of lasers, which were invented in 1960. It was developed around the same time as electron holography, which is used in transmission electron microscopes, that we are now familiar with and by the same scientist Dennis Gabor.

This microscope utilizes the principle of digital in-line holography. Very simply the main components are a small laser and a complementary metal oxide semiconductor imaging chip that is used as a platform. It uses a laser which when in contact with an object on a platform creates interference waves which are picked up by the chip, converted via several complex algorithms and displayed on a computer.

Figure 1: Schematic of in-line digital holography. The laser (L) illuminates a pinhole (P) which acts a point light source. Spherical waves are produced from the pinhole. First the waves illuminate the object (O) and produce reference waves ( ¾ )and interference waves (−−−) that constitute the hologram at the screen (C). (http://www.pnas.org/content/98/20/11301.full)

What are the advantages to this microscope? It has a larger field of view than traditional microscopes, which means the data it collects is more likely to be statistically significant. It’s also much smaller and portable, and it’s lack of significant hardware makes it easier to conduct experiments, especially when you want to keep your cells alive in an incubated environment.

At imec we’re using the lens-free imaging to track cancer cell migration. On paper it doesn’t sound that exciting, but in practice it means that the possibility of understanding how cancer cells work in 3-D environments within humans. This is exciting for a lot of reasons including the fact that we can change a variety of variables that will impact these cells. For example, we can treat cells with a chemotactic drug, image them and see how that impacts motility with the general hope that it will halt metastatic process. Of course there are lots of steps in between for these conclusions to be upheld, but in the meantime, I get to run experiments on breast and prostate cancer cells using a lens-free microscope.

Figure 2: Lens-free imaging prototype

A side note: the popular phrase “this is not a pipe” or “ceci n’est pas une pipe,” which was adapted for my title, is from René Magritte’s The Treachery of Images. Magritte is a Belgian surrealist artist who is featured in a four-story exhibition in the Royal Museum of Fine Arts in Brussels. The idea is that the pipe is only a representation since you can’t physically hold the pipe or fill it with tobacco. At the Royal Museum you can see an extensive collection of Magritte’s art as well as works from the Renaissance to the Contemporary periods.

Figure 3: “This Continues Not to be a Pipe” (a successor to “This is Not a Pipe”) featured at the Royal Museum of Fine Arts, Brussels. The original Treachery of Images is currently housed in the Los Angeles County Museum of Arts.

---Victoria Laney

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