Lensless Camera Uses X-rays

A lensless camera uses x-rays to take high-resolution images of ultrasmall structures buried inside nanoparticles, nanomaterials, and biological specimens.

Scientists at Argonne National Laboratory, in collaboration with those from the University of California at Los Angeles, the University of Melbourne, La Trobe University and the Australian Synchrotron, developed a way to examine internal and buried structures in micrometer-sized samples on the scale of nanometers, which is important to the understanding of how materials behave electrically, magnetically and under thermal and mechanical stress.

The technique, which can image whole biological cells such as cellular nuclei, has biological and biomedical applications that could lead to a better understanding of disease and its eradication, healing after injury, cancer and cell death.

X-rays are ideally suited for nanoscale imaging because of their ability to penetrate the interior of the object, but their resolution has traditionally been limited by lens technology. The new lensless technique avoids this limitation.

“There is no lens involved at all,” said Ian McNulty, the lead Argonne author on a new paper about the work in the journal Physical Review Letters. “Instead, a computer uses sophisticated algorithms to reconstruct the image. We expect this technique will enhance our understanding of many problems in materials and biological research.” The technique can be extended beyond the current resolution of about 20 nm to image the internal structure of micrometer-sized samples at finer resolution, reaching deeper into the sample than other types of microscopes.

Argonne National Laboratory scientists and collaborators used high energy x-rays from the Advanced Photon Source and a lensless camera to create detailed images of nanoscale materials. The scientists are working to develop a dedicated facility for the process at the lab. (Photo courtesy Argonne National Laboratory)

Electron microscopes, for example, can image structural details on the nanometer scale, but once the sample reaches sizes of a few micrometers and larger, the usefulness of these instruments to probe its internal structure is limited. In many cases, only the surface of the sample can be studied, or the sample must be sliced to view its interior, which can be destructive.

A collaborative team comprising members of the X-ray Microscopy and Imaging Group at Argonne’s Advanced Photon Source (APS) and a team led by professor John Miao at UCLA developed a powerful new extension of the new lensless imaging technique that enables high-resolution imaging of a specific element buried inside a sample.

The key is the high-intensity x-ray beams created at the APS. An intense, coherent x-ray beam collides with the sample, creating a diffraction pattern which is recorded by a CCD camera. The x-ray energy is tuned to an atomic resonance of a target element in the sample. Using sophisticated phase-recovery algorithms, a computer reconstructs an image of the specimen that highlights the presence of the element. The result is an image of the internal architecture of the sample at nanometer resolution and without destructive slicing. By using x-ray energies that coincide with an atomic absorption edge, the imaging process can distinguish between different elements in the sample.

If the nucleus or other parts of a cell are labeled with protein specific tags, it can be imaged within whole cells at a resolution far greater than that of ordinary microscopes.

The method also has applications in the nanoengineering field, which is working to develop more efficient catalysts for the petrochemical and energy industries and materials with electrically programmable mechanical, thermal and other properties.

“There are only a handful of places in the world this can be done and APS is the only place in the United States at these x-ray energies,” X-ray Microscopy and Imaging Group leader Qun Shen said. “We would eventually like to create a dedicated, permanent laboratory facility at the APS for this imaging technique that can be used by scientists on a routine basis.”

A dedicated facility would require building an additional beamline at the APS, which currently has 34 sectors, each containing one or more beamlines.

The research was funded by the Department of Energy's Office of Basic Energy Sciences and the National Science Foundation.

For more information, visit: www.anl.gov