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NEWS
June 2023 ESRFnews
The ESRF s ID13 nanobeam has virtually split a single bagworm silk fibre into 20 strands, to reveal its cross- sectional structure. Understanding the structure could help biophysicists develop artificial silks with comparable mechanical properties.
Bagworms get their name from the protective cases built by the caterpillar larvae, out of silk, twigs, lichen and other plant detritus. The silk itself has extraordinarily strong and tough mechanical properties, which could inspire new types of non-plastic synthetic fibres. Taiyo Yoshioka and Tsunenori Kameda at the National Agriculture and Food Organization in Tsukuba, Japan, together with Manfred Burghammer and Christian Riekel at ID13, subjected single bagworm fibres, about 5 μm in diameter, to scanning X-ray scattering at ID13. The beamline s small-to-wide angle scattering range, and ability to probe down to sub-micron resolutions, allowed the researchers to avoid signals from the more strongly scattering sericin coat layer, and visualise a homogeneous distribution of fibroin nanofibrils within.
The results confirmed recent modelling predictions that bagworm and spider silks derive their strength from mesoscale assembly, and have a gradient heterogeneous fibrillar structure (Nano Lett. 23 827). These results open up new possibilities for bottom-up modelling approaches of the mechanical properties of silk and for developing structural control techniques in artificial silk spinning, the researchers say.
Bagworms reveal silky secrets
The structure of a new piezoelectric material with outstanding electromechanical properties has been studied by time-resolved X-ray diffraction (XRD) at the ESRF s ID15A beamline.
Piezoelectric materials turn mechanical stress into electric polarisation, and are at the core of many transducers, actuators and sensors. Thanks to its easy manufacture and low cost, lead zirconate titanate (PZT) is one of the most popular ceramic piezoelectrics, but there are increasing demands to improve performance high piezoelectricity while maintaining high thermal and depolarisation stability.
One route to this is to texture ceramics, by tuning the orientation distribution of the constituent crystallites. Scientists led by the Xi an Jiaotong University and the Harbin Institute of Technology, both in China, and the University of Wollongong in Australia, have introduced such a method for PZT, based on a sacrificial crystalline template. At ID15A,
high-energy XRD revealed that the resultant piezoelectric is highly textured, with 94% of grains aligned; meanwhile, time-resolved in situ XRD demonstrated that its strain mechanism involves a polarisation rotation process between two crystallographic directions (Science 380 87). On one hand you need high flux at 80 keV, or higher, to get diffraction from bulk PZT while the electric field ramps at several kilovolts per second; on the other, you need a fast area detector and micron- precise sample positioning, says ID15A scientist Stefano Checchia. ID15A manages all of that.
John Daniels, one of the paper s authors at the University of New South Wales in Australia, says the new piezoelectric is good news for applications in medical diagnostics and precision manufacturing. These developments will contribute significantly to the advancement of technology and innovation in these fields, paving the way for more efficient and accurate applications, he adds.
The new piezoelectric (yellow spheres) is grown on a sacrificial template (yellow bars).
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ID15A probes new piezoelectric
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