#AtomicForceMicroscopy

Structural Elucidation of Citric Acid Cross-Linked Pectin and Its Impact on the Properties of Nanocellulose-Reinforced Packaging Films

Citric acid cross-linking is an effective strategy for modifying citrus pectin to enhance its performance in sustainable packaging applications. In this article, Chandra Mohan Chandrasekar, Daniele Carullo, Francesco Saitta, Tommaso Bellesia, Elena Caneva, Chiara Baschieri, Marco Signorelli, Dimitrios Fessas, Stefano Farris and Davide Romano, investigated the structural changes induced by citric acid cross-linking and their influence on the properties of nanocellulose-reinforced packaging films..

The authors demonstrated that cross-linking significantly alters the structure–property relationship of the biopolymer matrix, leading to improved film integrity and modified surface morphology. These results provide valuable insight into biopolymer modification strategies for the development of environmentally friendly packaging materials.

Atomic force microscopy (AFM) was employed to characterize the surface morphology of the films. Measurements were performed using a commercially available AFM instrument operated in contact resonance amplitude imaging (CRAI) mode. A NanoWorld Arrow-FMR AFM probe was used.

This AFM probe features a rectangular beam with a triangular free end and a tetrahedral tip (tip radius ~10 nm, tip height 10–15 μm), with a spring constant of 2.8 N/m and a resonance frequency of 75 kHz. Root mean square surface roughness values were calculated from at least five height-mode images.

Fig. 3. 2D synchronized correlation analysis of FTIR spectra for CLCP packaging film trials. [The intensity of the auto-peaks on the diagonal line represents the overall change in spectral intensity. The key region of interest is the strong auto-peak around 1700 cm−1, highlighted by

Full citation: Chandrasekar, C. M.; Carullo, D.; Saitta, F.; Bellesia, T.; Caneva, E.; Baschieri, C.; Signorelli, M.; Fessas, D.; Farris, S.; Romano, D. “Structural elucidation of citric acid cross-linked pectin and its impact on the properties of nanocellulose-reinforced packaging films.” International Journal of Biological Macromolecules 2025, 333(2), 148869. https://doi.org/10.1016/j.ijbiomac.2025.148869

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Nonlinear Optical Response in Layer-Stacked Gallenene with Ferroelectric Polarization

Layer-stacked gallenene is an emerging two-dimensional material with unique structural and electronic propertiesIn this article, M.Yunusa, A. K.Schulz, T.Parker, et al. investigated the nonlinear optical response of layer-stacked gallenene exhibiting ferroelectric polarization. The material was produced using a liquid metal-based synthesis approach and showed a phase transition associated with its stacked structure.

The authors demonstrated strong second harmonic generation (SHG) signals, revealing the nonlinear optical activity of gallenene and confirming its ferroelectric nature. These findings highlight the potential of gallenene as a novel functional 2D material for advanced optoelectronic and photonic applications.

Atomic force microscopy (AFM) was used to characterize transparent lamellar films and helical filaments. Measurements were performed using a commercially available AFM instrument operated in contact mode. A NanoWorld Arrow-CONTR AFM probe with a nominal force constant of 0.2 N/m and a resonance frequency of 14 kHz was used to obtain high-resolution surface morphology data.

*Figure 1*
Structure of gallenene and complex anatomy of supercooled liquid gallium. Mechanism for electrical and thermal perturbation. a) Illustration of hypothesized interaction of SHG response with SLG in linearly polarized light showing that thermal perturbations could align the 2D nanocrystals, allowing for an increased SHG medium at either temperature or electrical fields. An example HAADF image of gallenene flake sandwiched between two graphene layers, as depicted in (a) (far right microscope image). b) Structural reorganization of gallenene nanocrystals in the SLG leading to an intensity change in SHG signal as a result of thermal or electrical perturbation.

Full citation:

Yunusa, M.; Schulz, A. K.; Parker, T.; Schneider, F.; Elibol, K.; Predel, M.; Dzíbelová, J.; Rebmann, M.; Gorkan, T.; Ye, J.; Tan, J.-C.; Kang, W.; van Aken, P. A.; Meixner, A. J.; Durgun, E.; Kotakoski, J.; Zhang, D.; Sitti, M. Nonlinear Optical Response in Layer-Stacked Gallenene with Ferroelectric Polarization.

Advanced Materials 2025, 37(44), e01058.

https://doi.org/10.1002/adma.202501058

All-ferroelectric implementation of reservoir computing

In the article “All-ferroelectric implementation of reservoir computing”, published in Nature Communications, Zhiwei Chen, Wenjie Li, Shuai Dong, Z. Hugh Fan, Yihong Chen, Xubing Lu, Min Zeng, Minghui Qin, Guofu Zhou, Xingsen Gao, and Jun-Ming Liu report a novel approach for implementing reservoir computing (RC) using a monolithic, fully ferroelectric hardware platform. This work is a result of multidisciplinary collaboration among experts in ferroelectric materials, neuromorphic device engineering, and condensed matter physics.
Reservoir computing is a recurrent neural network model that excels at processing spatiotemporal data, typically requiring complex and heterogeneous hardware. In this study, the authors demonstrate that a single material system—epitaxially grown Pt/BiFeO₃/SrRuO₃ ferroelectric thin films—can simultaneously implement both volatile and nonvolatile functionalities required for RC. This is achieved through precise imprint field (E_imp) engineering, which modifies the polarization dynamics within the ferroelectric layer.
Two types of ferroelectric diodes (FDs) are fabricated from the same stack:
• Volatile FDs, grown at a oxygen pressure of 19 Pa, possess a nonzero imprint field, resulting in spontaneous polarization back-switching after the removal of input pulses. This gives rise to short-term memory and fading dynamics, which are ideal for temporal feature transformation in the reservoir layer.
• Nonvolatile FDs, grown at a oxygen pressure of 15 Pa, with minimal imprint field, exhibit stable long-term potentiation/depression (LTP/LTD), making them well-suited for synaptic weight storage in the readout layer.
The all-ferroelectric RC system was benchmarked on several temporal processing tasks:
• Chaotic Hénon map prediction with a normalized root-mean-square error (NRMSE) of 0.017,
• Waveform classification (NRMSE ≈ 0.13),
• Noisy handwritten digit recognition (up to 91.7% accuracy), and
• Curvature discrimination (100% accuracy).
The devices showed remarkable endurance (>10⁶ cycles), retention (>30 days), low variability (~8% cycle-to-cycle), and extremely low power consumption (~11.8 µW for volatile, ~140 nW for nonvolatile). These results affirm the potential of ferroelectric devices for ultralow-power, scalable neuromorphic computing.
To support these findings, the study employed high-resolution scanning probe microscopy techniques. Specifically, NanoWorld Arrow™ EFM conductive AFM probes were used for piezoresponse force microscopy (PFM). These measurements were critical in confirming that volatility and nonvolatility were governed by tunable imprint fields within the BiFeO₃ layer.
The exceptional electrostatic sensitivity, sharp tip radius, and stable mechanical properties of NanoWorld Arrow™ EFM probes were indispensable in characterizing the field-induced polarization behavior and validating the dual-mode operational framework of the ferroelectric diodes.
This work presents a significant advance in neuromorphic hardware, showing that imprint-field engineering in ferroelectric systems enables the unification of dynamic and static memory functions within a single material system. The integration of volatile and nonvolatile functions into a coherent architecture—combined with robust nanoscale characterization—offers a promising path toward compact, energy-efficient RC platforms based entirely on functional oxides.
Citation:
Chen, Z., Li, W., Dong, S., Fan, Z. H., Chen, Y., Lu, X., Zeng, M., Qin, M., Zhou, G., Gao, X., & Liu, J.-M. (2023). All-ferroelectric implementation of reservoir computing. Nature Communications, 14, 3851. https://doi.org/10.1038/s41467-023-39371-y Read full article here

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