A new, lensless X-ray technique which can capture images of ultra-small structures buried in nanoparticles and nanomaterials, as well as features within biological cells, like cellular mitochondria, has been developed at the Argonne National Laboratory. Such a technique could be important to help in the understanding of how materials act, and could have practical applications in biology and biomedicine for the understanding of disease, healing after injury, cancer and cell death.
A nanometer is equal to one billionth of a metre, and X-rays are well suited for nanoscale imaging due to their ability to penetrate objects. But x-ray resolution has up until now been limited by lens technology. The new lensless technique being developed at Argonne circumvents this limitation. A paper on the work appears in the journal Physical Review Letters.
“There is no lens involved at all,” said lead author Ian McNulty. “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.”
Other types of microscopes, such as electron microscopes, can image structural details on a nanometer scale, however, 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. Enter the lensless x-ray camera.
A team of scientists from Argonne and UCLA developed a powerful new extension of the new lensless imaging technique that enables high resolution imaging of a particular element buried inside of a sample.
High Intensity X-ray
The key technology used is high intensity X-ray beams created at the Advanced Photon Source at Argonne. A high intensity, coherent X-ray beam strikes the sample, creating a diffraction pattern that is recorded by a charge coupled device (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.