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Sep 26, 2016 | By Benedict

Researchers from École Polytechnique Fédérale de Lausanne (EPFL) have 3D printed nanometric-scale sensors for improving the performance of atomic force microscopes. The sensors can enhance the sensitivity and detection speed of the microscopes when their detection components are miniaturized.

3D printing has been used in the field of microscopy for some time now. A few years ago, the DoE’s Pacific Northwest National Laboratory developed a 3D printed smartphone adaptor which could turn a regular handset into a microscope. A year later, a Swiss startup named Scrona released µPeek, a portable microscope which would, amongst other things, enable users to view a 3D nanoprinted “selfie,” roughly the size of a grain of salt, which was being offered by Scrona as part of a Kickstarter campaign. Today brings another 3D printed microscopy project from Switzerland, this time a little more serious…

A group of researchers from EPFL has created 3D printed nanometric-scale sensors which can be used to improve the performance of atomic force microscopes, detailing their findings in a research paper. According to the researchers, atomic force microscopy works a bit like a tiny record player: a tiny cantilever with a nanometric tip passes over a sample and traces the sample’s relief, atom by atom, just like the needle of a turntable traces the grooves of a record. The up-and-down movements of the nanometric tip are recorded by a sensor, and the data collected by this sensor can be used to indicate a sample’s topography.

To improve atomic force microscopes, it is possible to miniaturize the cantilever of the sensor, a process that will reduce inertia, increase sensitivity, and speed up detection. The EPFL team managed to do this by using a 3D printed, 5-nanometer-thick sensor made with a nanoscale 3D printing process. “Using our method, the cantilever can be 100 times smaller,” said Georg Fantner, director of the laboratory.

Because the sensor needed to pick up movements smaller than an atom, special techniques were required. The researchers, together with Michael Huth’s lab at Goethe Universität at Frankfurt am Main, developed a sensor made up of highly conductive platinum nanoparticles surrounded by an insulating carbon matrix. Carbon isolates the electrons in normal conditions, but a quantum effect comes into play at the nano-scale, with some electrons jumping through the insulating material and traveling from one nanoparticle to the next. “It’s sort of like if people walking on a path came up against a wall and only the courageous few managed to climb over it,” said Fantner.

The nanoparticles move further away from each other and the electrons make fewer jumps when the sensor changes shape. Changes in the current therefore reveal sensor deformation and the composition of the sample. According to the researchers, the most challenging part of the project was 3D printing these nanoscale sensors while keeping total control over their structure and properties.

“In a vacuum, we distribute a precursor gas containing platinum and carbon atoms over a substrate. Then we apply an electron beam,” said Maja Dukic, lead author on the paper. “The platinum atoms gather and form nanoparticles, and the carbon atoms naturally form a matrix around them. By repeating this process, we can build sensors with any thickness and shape we want. We have proven that we could build these sensors and that they work on existing infrastructures. Our technique can now be used for broader applications, ranging from biosensors, ABS sensors for cars, to touch sensors on flexible membranes in prosthetics and artificial skin.”

The research paper, “Direct-write nanoscale printing of nanogranular tunnelling strain sensors for sub-micrometre cantilevers,” has been published in Nature Communications.

 

 

Posted in 3D Printing Technology

 

 

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