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1. A recyclable PANI/PAAMPSA nanocomposite with repeatable, rapid, autonomous self-healing, and unprecedented electro-mechanical properties

   https://doi.org/10.1007/s42114-025-01361-7  

   Duprey, Colton; Ajeev, Arya; Hong, Dajung; Webb, Katherine; Veres, Sarah; Chen, George; Linn, Emily; Lusvardi, Gina; Liu, Zhongqi; Wang, Ruigang; et al (September 2025, Advanced Composites and Hybrid Materials)

   Wearable sensors, stretchable electronics, and many soft robotic materials must have a balance of conductivity, stretchability, and robustness. Intrinsically conductive polymers offer a critical step toward improving wearable sensor materials due to their tunable conductivity, soft/compliant nature, and ability to complex with other coactive molecules (i.e., polyacids, small molecules). The addition of synergistic nanofillers has been shown to enhance the conductivity, self-healing, and mechanical properties of the polymers for soft robotics and wearable applications. The development of a robust polymer nanocomposite material that offers ultra-stretchability, an autonomous self-healing ability, and enhanced electronic properties has long eluded researchers. Herein, we show an aqueous polyaniline [PANI]:poly(2-acrylamido-2-methylpropane sulfonic acid) [PAAMPSA]:phytic acid [PA] polymer complex synthesized with 0.5 wt % silver nanowires (AgNW) to form a polymer nanocomposite with high electronic sensitivity, unique mechanical properties (a maximum strain of 4693%) and repeatable/autonomous self-healing efficiencies of greater than 98%. This AgNW polymer complex has an engineering strain higher than any reported hydrogel or other polymer-based sensor materials, in which the interface between the polymer matrix and the AgNW is hypothesized to be integral for the formation of the active electrically conductive network and unprecedented mechanical properties. To illustrate the remarkable sensitivity, the material was employed as a biomedical sensor (pulse, voice recognition, motion), topographical sensor, and high-sensitivity strain gauge. 

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2. Additive Manufacturing of Photocurable PVDF-Based Capacitive Sensor

   https://doi.org/10.1115/SMASIS2023-111151  

   Srinivasaraghavan Govindarajan, Rishikesh; Ren, Zefu; Madiyar, Foram; Kim, Daewon (September 2023, American Society of Mechanical Engineers)

   Abstract The demand for the capacitive sensor has attracted substantial attention in monitoring pressure due to its distinctive design and passive nature with versatile sensing capability. The effectiveness of the capacitive sensor primarily relies on the variation in thickness of the dielectric layer sandwiched between conductive electrodes. Additive manufacturing (AM), a set of advanced fabrication techniques, enables the production of functional electronic devices in a single-step process. Particularly, the 3D printing approach based on photocuring is a tailorable process in which the resin consists of multiple components that deliver essential mechanical qualities with enhanced sensitivity towards targeted measurements. However, the availability of photocurable resin exhibiting essential flexibility and dielectric properties for the UV-curing production process is limited. The necessity of a highly stable and sensitive capacitive sensor demands a photocurable polymer resin with a higher dielectric constant and conductive electrodes. The primary purpose of this study is to design and fabricate a capacitive device composed of novel photocurable Polyvinylidene fluoride (PVDF) resin utilizing an LCD process exhibiting higher resolution with electrodes embedded inside the substrate. The embedded electrode channels in PVDF substrate are filled with conductive silver paste by an injection process. The additively manufactured sensor provides pressure information by means of a change in capacitance of the dielectric material between the electrodes. X-Ray based micro CT-Scan ex-situ analysis is performed to visualize the capacitance based sensor filled with conductive electrodes. The sensor is tested to measure capacitance response with changes in pressure as a function of time that are utilized for sensitivity analysis. This work represents a significant achievement of AM integration in developing efficient and robust capacitive sensors for pressure monitoring or wearable electronic applications. 

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3. Thermal expansion of boron nitride nanotubes and additively manufactured ceramic nanocomposites

   https://doi.org/10.1088/1361-6528/ad933a  

   Wang, Dingli; Chen, Rachel; Anjum, Nasim; Ke, Changhong (November 2024, Nanotechnology)

   Abstract Controlling the thermal expansion of ceramic materials is important for many of their applications that involve high-temperature processing and/or working conditions. In this study, we investigate the thermal expansion properties of additively manufactured alumina that is reinforced with boron nitride nanotubes (BNNTs) over a broad temperature range, from room temperature to 900 °C. The coefficient of thermal expansion (CTE) of the BNNT-alumina nanocomposite increases with temperature but decreases with an increase in BNNT loading. The introduction of 0.6% BNNTs results in an approximate 16% reduction in the CTE of alumina. The observed significant CTE reduction of ceramics is attributed to the BNNT’s low CTE and ultrahigh Young’s modulus, and effective interfacial load transfer at the BNNT-ceramic interface. Micromechanical analysis, based onin situRaman measurements, reveals the transition of thermal-expansion-induced interface straining of nanotubes, which shifts from compression to tension inside the ceramic matrix under thermal loadings. This study provides valuable insights into the thermomechanical behavior of BNNT-reinforced ceramic nanocomposites and contributes to the optimal design of ceramic materials with tunable and zero CTE. 

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4. Rapid 3D Printing of Nanoporous Copper Powders via Micro-Clip

   https://doi.org/10.1115/MSEC2023-104610  

   Liu, Luyang; Kublik, Natalya; Azeredo, Bruno; Chen, Xiangfan (June 2023, ASME 2023 18th International Manufacturing Science and Engineering Conference)

   Abstract Three-dimensional (3D) printing of metal components through powder bed fusion, material extrusion, and vat photopolymerization, has attracted interest continuously. Particularly, extrusion-based and photopolymerization-based processes employ metal particle-reinforced polymer matrix composites (PMCs) as raw materials. However, the resolution for extrusion-based printing is limited by the speed-accuracy tradeoff. In contrast, photopolymerization-based processes can significantly improve the printing resolution, but the filler loading of the PMC is typically low due to the critical requirement on raw materials’ rheological properties. Herein, we develop a new metal 3D printing strategy by utilizing micro-continuous liquid interface printing (μCLIP) to print PMC resins comprising nanoporous copper (NP-Cu) powders. By balancing the need for higher filler loading and the requirements on rheological properties to enable printability for the μCLIP, the compositions of PMC resin were optimized. In detail, the concentration of the NP-Cu powders in the resins can reach up to 40 wt% without sacrificing the printability and printing speed (10 μm·s−1). After sintering, 3D copper structures with microscale features (470 ± 140 μm in diameter) manifesting an average resistivity of 150 kΩ·mm can be realized. In summary, this new strategy potentially benefits the rapid prototyping of metal components with higher resolution at faster speeds. 

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5. Investigation of Piezoelectricity and Resistivity of Surface Modified Barium Titanate Nanocomposites

   https://doi.org/10.3390/polym11122123  

   Sundar, Udhay; Lao, Zichen; Cook-Chennault, Kimberly (December 2019, Polymers)

   null (Ed.)

   Polymer-ceramic nanocomposite piezoelectric and dielectric films are of interest because of their possible application to advanced embedded energy storage devices for printed wired electrical boards. The incompatibility of the two constituent materials; hydrophilic ceramic filler, and hydrophobic epoxy limit the filler concentration, and thus, their piezoelectric properties. This work aims to understand the role of surfactant concentration in establishing meaningful interfacial layers between the epoxy and ceramic filler particles by observing particle surface morphology, piezoelectric strain coefficients, and resistivity spectra. A comprehensive study of nanocomposites, comprising non-treated and surface treated barium titanate (BTO), embedded within an epoxy matrix, was performed. The surface treatments were performed with two types of coupling agents: Ethanol and 3-glycidyloxypropyltrimethoxysilan. The observations of particle agglomeration, piezoelectric strain coefficients, and resistivity were compared, where the most ideal properties were found for concentrations of 0.02 and 0.025. This work demonstrates that the interfacial core-shell processing layer concentration influences the macroscopic properties of nanocomposites, and the opportunities for tuning interfacial layers for desirable characteristics of specific applications. 

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