Rice University researchers in Texas are using a technique to grab images of chemical processes that happen faster than most laboratory cameras are able to capture them.

The technique, super temporal resolution microscopy (STReM), allows scientists to view and gather useful information about fluorescing molecules at a frame rate 20 times faster than typical lab cameras allow.

STReM, which uses a rotating phase mask to encode fast dynamics in each camera frame, may help researchers understand processes that occur at interfaces like adsorption and desorption of proteins' or molecules’ trajectories as they move along two-dimensional surfaces.

“Super-resolution microscopy lets us image things smaller than about half of visible light’s wavelength—around 250 nanometers,” says Christy Landes, associate professor of chemistry and electrical and computer engineering. One barrier is that researchers cannot take pictures of anything faster than the frame rate.

Typical charge-coupled device (CCD) cameras max out at frame rates of 10 to 100 milliseconds, Landes says. While other techniques like electron microscopy can see materials at the subnanoscale, super-resolution microscopy has a distinct advantage for fragile samples like biomolecules: it doesn’t destroy them in the process.

STReM manipulates the phase of light to give the image at the detector a more complicated shape. This process has previously been used by other researchers to encode where the object is in three-dimensional space within an otherwise two-dimensional image.

The Rice lab’s contribution was to note that by manipulating the phase over time, it would also be possible to encode faster time resolutions within a slow image frame. Thus, the group designed and built a spinning phase mask.

The resulting images capture dynamic events that happen faster than the camera’s intrinsic frame rate. The shape of each image within a frame effectively gives it a unique time stamp.

The phase mask draws on work on the single-pixel camera—which creates an image by capturing just one pixel several thousand times in rapid succession—to design what amounts to a piece of plastic with variable thickness that distorts light en route to the CCD.

“Like the single-pixel camera, we’re doing compressive analysis,” Landes says. “With the static phase mask, three-dimensional information is compressed into a 2D image. In this particular case, we have compressed faster information into a slower camera frame rate. It’s a way to get more information in the pixels that you have.”