New Spectroscopy And High-resolution Microscopy Hybrid

Simultaneously observing chemical and physical properties on and beneath the surface of biological and synthetic materials will be possible with a microscope being developed at Oak Ridge National Laboratory.

Called the Hybrid Photonic Mode-Synthesizing Atomic Force Microscope, the device is unique. According to principal investigator Ali Passian of ORNL’s Quantum Information System group, the instrument combines the disciplines of nanospectroscopy and nanomechanical microscopy.

“Our microscope offers a noninvasive rapid method to explore materials simultaneously for their chemical and physical properties,” Passian said. “It allows researchers to study the surface and subsurface of synthetic and biological samples, which is a capability that until now didn’t exist.”

Nanoscale Resolution

The instrument retains all of the advantages of an atomic force microscope while simultaneously offering the potential for discoveries through its high resolution and subsurface spectroscopic capabilities.

“The originality of the instrument and technique lies in its ability to provide information about a material’s chemical composition in the broad infrared spectrum of the chemical composition while showing the morphology of a material’s interior and exterior with nanoscale – a billionth of a meter – resolution,” Passian said.

Researchers will be able to study samples ranging from engineered nanoparticles and nanostructures to naturally occurring biological polymers, tissues and plant cells.

atomic force microscopy

The first application as part of the Department of Energy’s BioEnergy Science Center was in the examination of plant cell walls under several treatments to provide submicron characterization.

The plant cell wall is a layered nanostructure of biopolymers such as cellulose. Scientists want to convert such biopolymers to free the useful sugars and release energy.

Broad Applications

Due to this new instrument’s impressive capabilities, the researcher team envisions broad applications.

“An urgent need exists for new platforms that can tackle the challenges of subsurface and chemical characterization at the nanometer scale,” said co-author Rubye Farahi. “Hybrid approaches such as ours bring together multiple capabilities, in this case, spectroscopy and high-resolution microscopy.”

Looking inside, the hybrid microscope consists of a photonic module that is incorporated into a mode-synthesizing atomic force microscope. The modular aspect of the system makes it possible to accommodate various radiation sources such as tunable lasers and non-coherent monochromatic or polychromatic sources.

L. Tetard, A. Passian, R. H. Farahi, T. Thundat & B. H. Davison
Opto-nanomechanical spectroscopic material characterization
Nature Nanotechnology (2015) doi:10.1038/nnano.2015.168

Illustration Credit: ORNL