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1. Viscoelastic Characterization of Poly(3-hexylthiophene): Determination of Young’s Modulus

   https://doi.org/10.1021/acsapm.3c00939  

   Mefferd, Branston E.; Nambiar, Visakhan V.; Lu, Hongbing; Stefan, Mihaela C. (August 2023, ACS Applied Polymer Materials)

   Kirk S. Schanze, editor-in-chief (Ed.)

   Nanoindentation is an optimal technique for the measurement of thin film mechanical properties. Polymers present a unique problem in that their response to loading is time-dependent. Due to this, many of the most common nanoindentation methods are not suitable for probing polymer nanoscale properties. Despite this issue being well-known for decades, poly(3-hexylthiophene) has been exclusively analyzed by time-independent mechanical properties testing methods. Herein, we present a nanoindentation technique that analyzes the materials’ time-dependent response under both constant rate loading and step loading. By determining viscoelastic functions, we are able to extract the Young’s relaxation modulus of poly(3- hexylthiophene). The average Young’s modulus acquired from viscoelastic nanoindentation is determined to be 260 ± 27 MPa. These results are in excellent agreement with specialized mechanical tests for thin 

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2. Surface Engineering of the Mechanical Properties of Molecular Crystals via an Atomistic Model for Computing the Facet Stress Response of Solids

   https://doi.org/10.1002/chem.202400779  

   Almehairbi, Mubarak; Joshi, Vikram_C; Irfan, Ahamad; Saeed, Zeinab_M; Alkhidir, Tamador; Abdelhaq, Aya_M; Managutti, Praveen_B; Dhokale, Bhausaheb; Jadhav, Thaksen; Calvin_Sun, Changquan; et al (May 2024, Chemistry – A European Journal)

   Abstract Dynamic molecular crystals are an emerging class of crystalline materials that can respond to mechanical stress by dissipating internal strain in a number of ways. Given the serendipitous nature of the discovery of such crystals, progress in the field requires advances in computational methods for the accurate and high–throughput computation of the nanomechanical properties of crystals on specific facets which are exposed to mechanical stress. Here, we develop and apply a new atomistic model for computing the surface elastic moduli of crystals on any set of facets of interest using dispersion–corrected density functional theory (DFT−D) methods. The model was benchmarked against a total of 24 reported nanoindentation measurements from a diverse set of molecular crystals and was found to be generally reliable. Using only the experimental crystal structure of the dietary supplement, L–aspartic acid, the model was subsequently applied under blind test conditions, to correctly predict the growth morphology, facet and nanomechanical properties of L–aspartic acid to within the accuracy of the measured elastic stiffness of the crystal, 24.53±0.56 GPa. This work paves the way for the computational design and experimental realization of other functional molecular crystals with tailor–made mechanical properties. 

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3. Elucidation of the Nano-Mechanical Property Evolution of 3D-Printed Zirconia

   https://doi.org/10.3390/micro5020024  

   Dantzler, Joshua_Z R; Leyva, Diana Hazel; Borgaro, Amanda L; Mahmud, Md Shahjahan; Lopez, Alexis; Zaman, Saqlain; Arroyo, Sabina; Lin, Yirong; Leyva, Alba Jazmin (June 2025, Micro)

   Understanding the mechanical properties of three-dimensional (3D)-printed ceramics while keeping the parts intact is crucial for advancing their application in high-performance and biocompatible fields, such as biomedical and aerospace engineering. This study uses non-destructive nanoindentation techniques to investigate the mechanical performance of 3D-printed zirconia across pre-conditioned and sintered states. Vat photopolymerization-based additive manufacturing (AM) was employed to fabricate zirconia samples. The structural and mechanical properties of the printed zirconia samples were explored, focusing on hardness and elastic modulus variations influenced by printing orientation and post-processing conditions. Nanoindentation data, analyzed using the Oliver and Pharr method, provided insights into the elastic and plastic responses of the material, showing the highest hardness and elastic modulus in the 0° print orientation. The microstructural analysis, conducted via scanning electron microscopy (SEM), illustrated notable changes in grain size and porosity, emphasizing the influencing of the printing orientation and thermal treatment on material properties. This research uniquely investigates zirconia’s mechanical evolution at the nanoscale across different processing stages—pre-conditioned and sintered—using nanoindentation. Unlike prior studies, which have focused on bulk mechanical properties post-sintering, this work elucidates how nano-mechanical behavior develops throughout additive manufacturing, bridging critical knowledge gaps in material performance optimization. 

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4. Modern strategies in classical fields of nanoindentation: Semiconductors, ceramics, and thin films

   https://doi.org/10.1557/s43577-025-00923-w  

   Fang, Xufei; Clausner, André; Hodge, Andrea_M; Sebastiani, Marco (May 2025, MRS Bulletin)

   Abstract Over the past three decades, nanoindentation has continuously evolved and transformed the field of materials mechanical testing. Once highlighted by the groundbreaking Oliver–Pharr method, the utility of nanoindentation has transcended far beyond modulus and hardness measurements. Today, with increasing challenges in developing advanced energy generation and electronics technologies, we face a growing demand for accelerated materials discovery and efficient assessment of mechanical properties that are coupled with modern machine learning-assisted approaches, most of which require robust experimental validation and verification. To this end, nanoindentation finds its unique strength, owing to its small-volume requirement, of fast-probing and providing a mechanistic understanding of various materials. As such, this technique meets the demand for rapid materials assessment, including semiconductors, ceramics, and thin films, which are integral to next-generation energy-efficient and high-power electronic devices. Here, we highlight modern nanoindentation strategies using novel experimental protocols outlined by the use of nanoindentation for characterizing functional structures, dislocation engineering, high-speed nanoindentation mapping, and accelerating materials discovery via thin-film libraries. We demonstrate that nanoindentation can be a powerful tool for probing the fundamental mechanisms of elasticity, plasticity, and fracture over a wide range of microstructures, offering versatile opportunities for the development and transition of functional materials. Graphical abstract 

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5. Nanoindentation measurement of core–skin interphase viscoelastic properties in a sandwich glass composite

   https://doi.org/10.1007/s11043-020-09448-y  

   Cao, Dongyang; Malakooti, Sadeq; Kulkarni, Vijay N.; Ren, Yao; Lu, Hongbing (April 2020, Mechanics of Time-Dependent Materials)

   Debonding at the core–skin interphase region is one of the primary failure modes in core sandwich composites under shear loads. As a result, the ability to characterize the mechanical properties at the interphase region between the composite skin and core is critical for design analysis. This work intends to use nanoindentation to characterize the viscoelastic properties at the interphase region, which can potentially have mechanical properties changing from the composite skin to the core. A sandwich composite using a polyvinyl chloride foam core covered with glass fiber/resin composite skins was prepared by vacuum-assisted resin transfer molding. Nanoindentation at an array of sites was made by a Berkovich nanoindenter tip. The recorded nanoindentation load and depth as a function of time were analyzed using viscoelastic analysis. Results are reported for the shear creep compliance and Young’s relaxation modulus at various locations of the interphase region. The change of viscoelastic properties from higher values close to the fiber composite skin region to the smaller values close to the foam core was captured. The Young’s modulus at a given strain rate, which is also equal to the time-averaged Young’s modulus across the interphase region was obtained. The interphase Young’s modulus at a loading rate of 1 mN/s was determined to change from 1.4 GPa close to composite skin to 0.8 GPa close to the core. This work demonstrated the feasibility and effectiveness of nanoindentation-based interphase characterizations to be used as an input for the interphase stress distribution calculations, which can eventually enrich the design process of such sandwich composites. 

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