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Advanced Materials (Deerfield Beach,... Jun 2024Light-responsive liquid crystal elastomers (LCEs) are stimuli-responsive materials that facilitate the conversion of light energy into a mechanical response. In this...
Light-responsive liquid crystal elastomers (LCEs) are stimuli-responsive materials that facilitate the conversion of light energy into a mechanical response. In this work, a novel polysiloxane-based LCE with donor-acceptor Stenhouse adduct (DASA) side-chains was synthesized using a late-stage functionalization strategy. We demonstrate that this approach does not compromise the molecular alignment observed in the traditional Finkelmann method. This easy, single-batch process provides a robust platform to access well-aligned, light-responsive LCE films with thickness ranging from 400 μm to a fourteen-layer stack that is 5 mm thick. Upon irradiation with low-intensity broadband visible light (100 to 200 mW cm), these systems undergo 2D planar actuation and complete bleaching. Conversely, exposure to higher-intensity visible light induces bending followed by contraction (300 mW cm). These processes are repeatable over several cycles. Finally, we demonstrate how light intensity and the resulting heat generation influences the photothermal stationary state equilibrium of DASA, thereby controlling its photoresponsive properties. This work establishes the groundwork for advancement of LCE-based actuators beyond thin film and UV-light reliant systems. This article is protected by copyright. All rights reserved.
PubMed: 38899577
DOI: 10.1002/adma.202404932 -
ACS Applied Materials & Interfaces Jun 2024Exploring a convenient, scalable, yet effective broadband electromagnetic wave absorber (EMA) in the gigahertz (GHz) region is of high interest today to quench its...
Exploring a convenient, scalable, yet effective broadband electromagnetic wave absorber (EMA) in the gigahertz (GHz) region is of high interest today to quench its expanding demand. Ni-Zn ferrite is considered as a potential EMA; however, their performance study as a scalable effective millimeter-length absorber is still limited. Herein, we investigated EM wave attenuation properties of NiZnFeO (NZF) samples substituting Mn ion in place of Fe as well as Zn within a widely used frequency range of 0.1-9 GHz. Through composition optimization, NiZnMnFeO (NZM0.1F) EMA demonstrates excellent microwave absorption performance accompanied by simultaneous maximum reflection loss (RL) of -50.2 dB and wide BW of 6.8 GHz (with RL < -10 dB, i.e., attenuation >90%) at an optimum thickness of 6 mm. Moreover, the attenuation constant significantly increases from ∼217 to 301 Np/m with Mn doping. The key contribution arises from magnetic-dielectric properties synergy along with enhanced dielectric and magnetic losses owing to cation chemistry and site occupation in spinel NZF. In addition, porosity is induced in the system by a controlled two-step heat treatment process that promotes total loss with multiple internal reflections of the EM wave. Furthermore, RL is simulated by varying incident EM wave angles for the NZM0.1F sample displaying its angle insensitivity up to 50°. Our results reveal NZM0.1F as a futuristic environment-friendly microwave absorber material that is suitable for practical high-frequency applications.
PubMed: 38899405
DOI: 10.1021/acsami.4c06498 -
ACS Applied Materials & Interfaces Jun 2024Recently emerged lead halide perovskite CsPbX (X = Cl, Br, and I) nanocrystals (PNCs) have attracted tremendous attention due to their excellent optical properties....
Recently emerged lead halide perovskite CsPbX (X = Cl, Br, and I) nanocrystals (PNCs) have attracted tremendous attention due to their excellent optical properties. However, the poor water stability, unsatisfactory luminescence efficiency, disappointing lead leakage, and toxicity have restricted their practical applications in photoelectronics and biomedical fields. Herein, a controllable encapsulated strategy is investigated to realize CsPbX PNCs/PVP @PMMA composites with superior luminescence properties and excellent biocompatibility. Additionally, the synthesized CsPbBr and CsPbBrI PNCs/PVP@PMMA structures exhibit green and red emissions with a maximal photoluminescence quantum yield (PLQY) of about 70.24% and 98.26%, respectively. These CsPbX PNCs/PVP@PMMA structures show high emission efficiency, excellent stability after water storage for 18 months, and low cytotoxicity at the PNC concentration at 500 μg mL. Moreover, white light-emitting diode (WLED) devices based on mixtures of CsPbBr and CsPbBrI PNCs/PVP@PMMA perovskite structures are investigated, which exhibit excellent warm-white light emissions at room temperature. A flexible manipulation method is used to fabricate the white light emitters based on these perovskite composites, providing a fantastic platform for fabricating solid-state white light sources and full-color displays.
PubMed: 38896470
DOI: 10.1021/acsami.4c06854 -
Small (Weinheim An Der Bergstrasse,... Jun 2024Following the diverse structural characteristics and primary usage, diamond products include nano-polycrystalline diamond (NPD), micron-polycrystalline diamond (MPD),...
Following the diverse structural characteristics and primary usage, diamond products include nano-polycrystalline diamond (NPD), micron-polycrystalline diamond (MPD), diamond film, porous diamond, and diamond wire drawing die. Among them, porous diamond possesses a distinctive combination of flexible surface functionality and a remarkably high surface area-to-volume ratio (SA/V) compared to traditional bulk materials, which contributes to cross-cutting applications in catalysis, adsorption, and electrochemistry while retaining the superior traits of diamond, particularly its exceptional chemical inertia. To avoid etching or microwave plasma chemical vapor deposition (MPCVD) techniques, this study proposes a high-temperature and high-pressure method based on a soluble skeleton (HPHT-ss) as an efficient and inexpensive approach for synthesizing millimeter-level porous diamonds. Interestingly, porous diamond synthesized by HPHT-ss exhibits multiscale pores distributed as macropores (average 75 µm) and mesopores (average 19 nm), which gives it a unique feature compared with other methods. Pertinent temperature-pressure conditions, HPHT-ss synthesis, and the formation mechanism of porous diamonds are also thoroughly discussed.
PubMed: 38895965
DOI: 10.1002/smll.202310316 -
Sensors (Basel, Switzerland) Jun 2024The research on high-precision and all-scenario localization using the millimeter-wave (mmWave) band is of great urgency. Due to the characteristics of mmWave, blockages...
The research on high-precision and all-scenario localization using the millimeter-wave (mmWave) band is of great urgency. Due to the characteristics of mmWave, blockages make the localization task more complex. This paper proposes a cooperative localization system among user equipment (UEs) assisted by reconfigurable intelligent surfaces (RISs), which considers device-to-device (D2D) communication. RISs are used as anchor points, and position estimation is achieved through signal exchanges between UEs. Firstly, we establish a localization model based on this system and derive the UEs' positioning error bound (PEB) as a performance metric. Then, a UE-RIS joint beamforming design is proposed to optimize channel state information (CSI) with the objective of achieving the minimum PEB. Finally, simulation analysis demonstrates the advantages of the proposed scheme over RIS-assisted base station positioning, achieving centimeter-level accuracy with a 10 dBm lower transmission power.
PubMed: 38894484
DOI: 10.3390/s24113694 -
Sensors (Basel, Switzerland) Jun 2024This study explored an indoor system for tracking multiple humans and detecting falls, employing three Millimeter-Wave radars from Texas Instruments. Compared to...
This study explored an indoor system for tracking multiple humans and detecting falls, employing three Millimeter-Wave radars from Texas Instruments. Compared to wearables and camera methods, Millimeter-Wave radar is not plagued by mobility inconveniences, lighting conditions, or privacy issues. We conducted an initial evaluation of radar characteristics, covering aspects such as interference between radars and coverage area. Then, we established a real-time framework to integrate signals received from these radars, allowing us to track the position and body status of human targets non-intrusively. Additionally, we introduced innovative strategies, including dynamic Density-Based Spatial Clustering of Applications with Noise (DBSCAN) clustering based on signal SNR levels, a probability matrix for enhanced target tracking, target status prediction for fall detection, and a feedback loop for noise reduction. We conducted an extensive evaluation using over 300 min of data, which equated to approximately 360,000 frames. Our prototype system exhibited a remarkable performance, achieving a precision of 98.9% for tracking a single target and 96.5% and 94.0% for tracking two and three targets in human-tracking scenarios, respectively. Moreover, in the field of human fall detection, the system demonstrates a high accuracy rate of 96.3%, underscoring its effectiveness in distinguishing falls from other statuses.
PubMed: 38894451
DOI: 10.3390/s24113660 -
Sensors (Basel, Switzerland) May 2024With the continuous development of automotive intelligence, vehicle occupant detection technology has received increasing attention. Despite various types of research in...
With the continuous development of automotive intelligence, vehicle occupant detection technology has received increasing attention. Despite various types of research in this field, a simple, reliable, and highly private detection method is lacking. This paper proposes a method for vehicle occupant detection using millimeter-wave radar. Specifically, the paper outlines the system design for vehicle occupant detection using millimeter-wave radar. By collecting the raw signals of FMCW radar and applying Range-FFT and DoA estimation algorithms, a range-azimuth heatmap was generated, visually depicting the current status of people inside the vehicle. Furthermore, utilizing the collected range-azimuth heatmap of passengers, this paper integrates the Faster R-CNN deep learning networks with radar signal processing to identify passenger information. Finally, to test the performance of the detection method proposed in this article, an experimental verification was conducted in a car and the results were compared with those of traditional machine learning algorithms. The findings indicated that the method employed in this experiment achieves higher accuracy, reaching approximately 99%.
PubMed: 38894124
DOI: 10.3390/s24113334 -
Sensors (Basel, Switzerland) May 2024Autonomous driving technology is considered the trend of future transportation. Millimeter-wave radar, with its ability for long-distance detection and all-weather... (Review)
Review
Autonomous driving technology is considered the trend of future transportation. Millimeter-wave radar, with its ability for long-distance detection and all-weather operation, is a key sensor for autonomous driving. The development of various technologies in autonomous driving relies on extensive simulation testing, wherein simulating the output of real radar through radar models plays a crucial role. Currently, there are numerous distinctive radar modeling methods. To facilitate the better application and development of radar modeling methods, this study first analyzes the mechanism of radar detection and the interference factors it faces, to clarify the content of modeling and the key factors influencing modeling quality. Then, based on the actual application requirements, key indicators for measuring radar model performance are proposed. Furthermore, a comprehensive introduction is provided to various radar modeling techniques, along with the principles and relevant research progress. The advantages and disadvantages of these modeling methods are evaluated to determine their characteristics. Lastly, considering the development trends of autonomous driving technology, the future direction of radar modeling techniques is analyzed. Through the above content, this paper provides useful references and assistance for the development and application of radar modeling methods.
PubMed: 38894100
DOI: 10.3390/s24113310 -
Polymers May 2024In tissue engineering, electrospinning has gained significant interest due to its highly porous structure with an excellent surface area to volume ratio and fiber...
In tissue engineering, electrospinning has gained significant interest due to its highly porous structure with an excellent surface area to volume ratio and fiber diameters that can mimic the structure of the extracellular matrix. Bioactive substances such as growth factors and drugs are easily integrated. In many applications, there is an important need for small tubular structures (I.D. < 1 mm). However, fabricating sub-millimeter structures is challenging as it reduces the collector area and increases the disturbing factors, leading to significant fiber loss. This study aims to establish a reliable and reproducible electrospinning process for sub-millimeter tubular structures with minimized material loss. Influencing factors were analyzed, and disturbance factors were removed before optimizing control variables through the design-of-experiments method. Structural and morphological characterization was performed, including the yield, thickness, and fiber arrangement of the scaffold. We evaluated the electrospinning process to enhance the manufacturing efficiency and reduce material loss. The results indicated that adjusting the voltage settings and polarity significantly increased the fiber yield from 8% to 94%. Variations in the process parameters also affected the scaffold thickness and homogeneity. The results demonstrate the complex relationship between the process parameters and provide valuable insights for optimizing electrospinning, particularly for the cost-effective and reproducible production of small tubular diameters.
PubMed: 38891422
DOI: 10.3390/polym16111475 -
Nature Communications Jun 2024Untethered miniature soft robots have significant application potentials in biomedical and industrial fields due to their space accessibility and safe human interaction....
Untethered miniature soft robots have significant application potentials in biomedical and industrial fields due to their space accessibility and safe human interaction. However, the lack of selective and forceful actuation is still challenging in revolutionizing and unleashing their versatility. Here, we propose a focused ultrasound-controlled phase transition strategy for achieving millimeter-level spatially selective actuation and Newton-level force of soft robots, which harnesses ultrasound-induced heating to trigger the phase transition inside the robot, enabling powerful actuation through inflation. The millimeter-level spatial resolution empowers single robot to perform multiple tasks according to specific requirements. As a concept-of-demonstration, we designed soft robot for liquid cargo delivery and biopsy robot for tissue acquisition and patching. Additionally, an autonomous control system is integrated with ultrasound imaging to enable automatic acoustic field alignment and control. The proposed method advances the spatiotemporal response capability of untethered miniature soft robots, holding promise for broadening their versatility and adaptability.
Topics: Robotics; Equipment Design; Humans; Ultrasonic Waves; Phase Transition; Ultrasonography
PubMed: 38890294
DOI: 10.1038/s41467-024-49148-6