3D Printing

New Graphene Scanner Working at Frequencies in the Terahertz Band

Javier Gutiérrez is excited about a next generation, Graphene-based scanner being developed by a group of researchers in Europe, which will help unveil undiscovered properties and details of historical objects and works of art, while preserving their material integrity. Javier is a researcher at Treelogic and coordinator of Insidde, the Seventh Framework Program – A European Union funded project within which this work falls, and in which eight organizations from five European countries are participating.

The scanner allows for observation of the way in which the brushes to these historic works of art. Laurens van der Maaten from Delft University of Technology explains the significance, saying: “The scanner may show details on how a painting was made that are of great art-historical value, because they tell us more about how the painter worked; these details are also extremely helpful for conservators when preparing for the restoration of paintings.”

Even though the scanner is still in its trial and calibration phase, the researchers have already managed to use it to identify some of the materials found in specific works of art, much to the excitement of participating museum staff.  Marta Flórez (Museum of Fine Arts of Asturias), said, “We didn’t expect to get this type of information, but with the prototype we have been able to clearly distinguish between some pigments, which in some cases will avoid having to puncture the painting in order to find out what materials the artist used.”

3d scanning paintings
(a) Still life. (b) Reproduction used for test and validation purposes. (c) Samples to be analysed with the terahertz scanner consisting of multiple pigments found in the original painting.

Paintings have a planar surface, and researchers are testing and adjusting the scanner in order to be able to generate images of sealed three-dimensional objects. For this, a structured-light scanner will be combined with the terahertz scanner.

Geert Willems, Director R&D of 4DDynamics explains the benefit: “By reconstructing the 3D shape of the objects, we can help guide the terahertz scanner to the optimal positions around the curved shape of the objects, while making sure the scanner does not come in actual contact with the artwork”.  As for future objects and works to be scanned, they will be capturing “various Bulgarian pots from the 3rd century which were sealed when they were found, and whose contents are unknown.”

Reneta Karamanova, restorer at the Regional Museum of History Stara Zagora, adds “Another valuable application of the scanner to archaeologists and restorers is its use to identify painted, carved or embossed decoration of pottery on which surface there are deposits of dust or limestone. The ascertainment of the condition of the ceramic surface by terahertz analysis would prevent the damage that can be caused to the vessel by manual cleaning of the deposits.”

The arrival of this scanner has two practical applications.  The first is extending the size of the spectral region usually investigated. The second is to create more accessibility for the use of THz imaging analysis in the world of art.

3d scan paintings
(a) Ceramic from the III century. (b) Setup for 3D acquisition with a structured light scanner. (c) 3D model resulting from raw data before post-processing.

Mounted on what is referred to as the “XYZ table”, which measures 1.50 x 1.50 meters and is 1.20 meters high, the scanner comprises multiple heads which incorporate graphene emitters and receptors and can move three-dimensionally across the 2 square meter work area.  As of now, x-rays, infra-red or ultraviolet radiation techniques are generally used to measure this type of physical data.

Samuel Ver Hoeye, technical coordinator of the project, described how the analogous sets of frequency ranges collect data, saying that each one “has a different capability in terms of penetrating the different layers of a piece of work, so the information that is recovered with each technique is complementary to the others.”

If you don’t know too much about graphene, it is formed by carbon atoms in a single layer only one atom thick, and when submitted to electromagnetic waves, it behaves in a non-linear way, “kind of frequency multiplier. If we make a wave of a particular frequency impinge on graphene, the graphene has the ability to emit another, higher, frequency”, according to David Gómez and Nuria Campos from ITMA Materials Technology.

Until recently, the emission of frequencies in the terahertz band has been accomplished mainly in experimental settings.  In the terahertz band, frequencies are lower than infra-red but higher than those used by mobile phones and satellite communications.