Controllable Formation of Luminescent Carbon Quantum Dots Mediated by the Fano Resonances Formed in Oligomers of Gold Nanoparticles

Rapid and controllable formation of fluorescent carbon quantum dots (CQDs) is highly desirable in the fields of nanophotonics and biophotonics. Here, a novel strategy for creating CQDs, which emit white light efficiently under the excitation of either laser light or a mercury lamp, is proposed and demonstrated. The luminescent CQDs are generated by irradiating a poly(vinyl alcohol) (PVA) film doped with dense gold nanoparticles (AuNPs) with femtosecond laser pulses. The creation of CQDs from PVA is a two‐step dehydration process mediated by AuNPs which act not only as heat sources but also as catalytic agents. The formation of C?C, C? C, and C? O bonds is confirmed by infrared Fourier transformation spectroscopy and X‐ray photoelectron spectroscopy. It is revealed both numerically and experimentally that a spatially localized temperature distribution at the deep subwavelength scale can be achieved in oligomers of AuNPs by resonantly exciting the Fano resonances formed in the oligomers of AuNPs, enabling the generation of CQDs with small diameters. As one of the potential applications, it is demonstrated that optical display and optical data storage with ultralow energy can be realized by selectively introducing luminescent CQDs in the AuNP/PVA film.     

Multifunctional Janus Microplates Arrays Actuated by Magnetic Fields for Water/Light Switches and Bio‐Inspired Assimilatory Coloration

Smart dynamic regulation structured surfaces, inspired by nature, which can dynamically change their surface topographies under external stimuli for convertible fluidic and optical properties, have recently motivated significant interest for scientific research and industrial applications. However, there is still high demand for the development of multifunctional dynamically transformable surfaces using facile preparation strategies. In this work, a type of Janus high‐aspect‐ratio magnetically responsive microplates array (HAR‐MMA) is readily fabricated by integrating a flexible laser scanning strategy, smart shape‐memory‐polymer‐based soft transfer, and a simple surface treatment. By applying external magnetic field, instantaneous and reversible deformation of Janus HAR‐MMA can be actuated, so surface wettability can be reversibly switched between superhydrophobic (158°) and hydrophilic (40°) states, based on which a novel magnetically responsive water droplet switch can be realized. Moreover, inspired by the biological assimilatory coloration of chameleons, dynamically color conversion can be skillfully realized by applying different colors on each side of the Janus HAR‐MMA. Finally, as a proof‐of‐concept demonstration in light manipulation, a HAR‐MMA is applied as an optical shutter actuated by external magnetic field with eximious controllability and repeatability. The developed multifunctional HAR‐MMA provides a versatile platform for microfluidic, biomedical, and optical applications.     

4D Direct Laser Writing of Submerged Structural Colors at the Microscale

Biomimetic stimuli-responsive structure colors (SCs) can improve the visualization and identification in the micro functional structure field such as information encryption/decryption and smart actuators. However, it is still challenging to develop the ability to 4D print arbitrary submerged colorful patterns with stimuli-responsive materials at the microscale. Herein, a hydrogel photoresist with feature resolution (98 nm) for the fabrication of 4D microscopic SCs by the femtosecond direct laser writing method is developed. The 4D printed woodpile SCs are grouped as pixel palettes with various laser parameters and they spanned almost the entire color space. The coloring mechanism of diffraction gratings is not only investigated by optics microscopy and spectroscopy but also supported by simulation. Moreover, the 4D printed hydrogel-integrated amphichromatic fish constructions and pixelated painting can visually discolor reversibly by regulating the solution pH. This finding promises an ideal coloring method for sensors, anti-counterfeiting labels, and transformable photonic devices.     

Splashing-Assisted Femtosecond Laser-Activated Metal Deposition for Mold- and Mask-Free Fabrication of Robust Microstructured Electrodes for Flexible Pressure Sensors (Small 24/2023)

Flexible pressure sensors play an indispensable role in flexible electronics. Microstructures on flexible electrodes have been proven to be effective in improving the sensitivity of pressure sensors. However, it remains a challenge to develop such microstructured flexible electrodes in a convenient way. Inspired by splashed particles from laser processing, herein, a method for customizing microstructured flexible electrodes by femtosecond laser-activated metal deposition is proposed. It takes advantage of the catalyzing particles scattered during femtosecond laser ablation and is particularly suitable for moldless, maskless, and low-cost fabrication of microstructured metal layers on polydimethylsiloxane (PDMS). Robust bonding at the PDMS/Cu interface is evidenced by the scotch tape test and the duration test over 10 000 bending cycles. Benefiting from the firm interface, the developed flexible capacitive pressure sensor with microstructured electrodes presents several conspicuous features, including a sensitivity (0.22 kPa⁻¹) 73 times higher than the one using flat Cu electrodes, ultralow detection limit (<1 Pa), rapid response/recovery time (4.2/5.3 ms), and excellent stability. Moreover, the proposed method, inheriting the merits of laser direct writing, is capable of fabricating a pressure sensor array in a maskless manner for spatial pressure mapping.     

基于光谱控制与色散优化的飞秒啁啾脉冲放大系统

飞秒激光在工业加工、精密测量、军事国防、科学研究等领域具有广阔的应用前景。报道了基于光谱控制与色散优化的高功率、高脉冲质量飞秒啁啾脉冲放大系统。利用与压缩器色散量相匹配的色散可调啁啾布拉格光纤光栅(CFBG)作为展宽器,通过微调CFBG色散量补偿系统的残余色散使整个系统的净色散趋于零;同时引入光谱滤波等手段,保证入射到主放大器之前的脉冲光谱形状不发生畸变,避免了放大过程中脉冲质量的劣化。最终获得了重复频率为50 MHz、平均功率为24 W、脉冲宽度为198 fs的高脉冲质量飞秒激光输出。     

飞秒激光加工红磷的实验研究

为了验证飞秒激光加工含能材料的安全性,本文 以红磷作为含能材料替代物,从理论和实验上说明飞 秒激光加工红磷“冷加工”和“热加工”的可控性。利用有限元软件分析了单脉冲飞秒激光 作用到红磷表 面后样品的径向和轴向温度分布,得到了红磷的热影响区域。通过实验结果验证了飞秒激光 加工红磷样品 时具有“冷加工”和“热加工”两个区域,分析了激光通量对“冷加工”和“热加工”的影 响,确定了加 工红磷样品的“冷加工”的激光通量范围,并计算得到了红磷样品的烧蚀阈值和脉冲累积因 子。     

非接触式喷嘴旋流槽测量系统的搭建与实现

针对航空发动机燃油喷嘴组件的旋流槽特征的精密快速检测难题,本文采用锥光偏振全息采样技术与多轴联动定位技术相结合的方式,搭建了非接触式的喷嘴旋流槽测量系统,可以实现喷嘴旋流槽的槽深、旋流角度和槽宽等几何参数的扫描测量。该系统主要由机械本体、光学测头、运动控制系统和喷嘴专用夹具等构成,其机械本体设计为紧凑的立柱式结构,运动机构包括三个直线轴和一个回转轴,控制系统采用主流工控机与通用坐标测量机控制器相结合的二级位置闭环数字复合控制方式,并应用高精度的免校准加工及检测专用夹具来实现被测喷嘴零件的安装和定位。最后,应用该系统对某喷嘴样件的旋流槽特征进行了多次重复测量。实验结果表明,本文所搭建的非接触式喷嘴旋流槽测量系统能够完成既定的测量任务,而且系统的重复性测量精度能够满足检测任务需求,因而可以作为一项喷嘴结构尺寸检测的技术解决方案。     

飞秒激光组装一维纳米材料及其应用

一维纳米材料具有众多优异的特性,是构建微纳米功能性器件的基石。实现一维纳米材料在二维和三维空间的高精度和高定向组装是充分发挥其应用潜力的关键,同时也是制造难点。在众多纳米材料组装技术中,飞秒激光直写诱导组装技术具有独特优势,可实现一维纳米材料在任意三维结构中的可设计、高定向及高精度的组装。首先简要介绍了一维纳米材料组装研究的背景,并总结了非激光直写组装技术的研究现状和存在的挑战,然后较详细介绍了飞秒激光直写技术在一维纳米材料组装研究中的进展,重点回顾了金属(包括Au和Ag纳米线)、半导体(包括CNTs和ZnO)一维纳米材料的飞秒激光直写组装及微纳光电子功能器件的制造。并讨论了诱导一维纳米材料定向排布的光学力和非光学力(包括剪切力、体积收缩应力和空间限制)的作用机理,理论计算和实验研究结果验证了飞秒激光诱导的非光学力作用是导致一维纳米材料定向排布的主要原因。最后探讨了目前飞秒激光组装技术面临的一些问题和未来在高精度纳米材料组装和三维功能器件集成方面的发展趋势。     

Elastic Janus film for Wound Dressings: Unidirectional Biofluid Transport and Effectively Promoting Wound Healing

The intrinsic hydrophilicity of conventional dressings cannot achieve effective management of excessive biofluid around the wound bed, which inevitably causes infection and hinders wound healing. In addition, present dressings such as medical gauze or band aids have a limited stretching capability, which does not comply well with the skin deformation during muscle movement, thus impacting patient comfort. Herein, a Janus wound dressing is reported by assembling an external hydrophobic (HP) adhesive tape, a filter paper, and a polydimethylsiloxane (PDMS) Janus film. The PDMS Janus film as the primary dressing can unidirectionally remove biofluid away from the wound bed. The mechanism of the unidirectional biofluid transport is investigated, demonstrating that the stretching or bending of the Janus dressing is beneficial for unidirectional biofluid draining. It indicates that the Janus PDMS film has potential for practical applications on stretched or bended skin surface. In addition, in order to prevent bacterial infection, amoxicillin powder is uniformly encapsulated on the HP layer of Janus film, resulting in faster wound healing. This study is valuable for designing and fabricating next-generation dressings with high performance for clinical applications.     

基于新型传感器阵列的声全息测试分析方法研究

针对声全息技术在实际工程应用中的扫描相位误差和有限测量孔径的问题,通过改进测试阵列和算法优化两种途径对其进行分析和解决.使用基于数字麦克风的面阵进行快照法测量,代替了传统的扫描测量,规避了扫描引入的相位误差;从理论上分析了有限孔径下近场声全息重构误差产生机理,并提出了"有限孔径空间扩展+波数域迭代滤波"的声全息算法,选用简谐激励作用下四周为无限大障板的简支钢板为对象,与传统声全息算法结果对比,验证了算法的有效性,并分析了全息面数据空间补零长度和迭代循环次数对声场重构的影响;使用转子台作为被测设备,模拟已知故障,通过单参考源下传感器阵列扫描测量结果验证了算法可以准确地定位模拟故障的空间位置.