Design of Hierarchical Beads for Efficient Label‐Free Cell Capture

Defined hierarchical materials promise cell analysis and call for application‐driven design in practical use. The further issue is to develop advanced materials and devices for efficient label‐free cell capture with minimum instrumentation. Herein, the design of hierarchical beads is reported for efficient label‐free cell capture. Silica nanoparticles (size of ≈15 nm) are coated onto silica spheres (size of ≈200 nm) to achieve nanoscale surface roughness, and then the rough silica spheres are combined with microbeads (≈150–1000 µm in diameter) to assemble hierarchical structures. These hierarchical beads are built via electrostatic interaction, covalent bonding, and nanoparticle adherence. Further, after functionalization by hyaluronic acid (HA), the hierarchical beads display desirable surface hydrophilicity, biocompatibility, and chemical/structural stability. Due to the controlled surface topology and chemistry, HA‐functionalized hierarchical beads afford high cell capture efficiency up to 98.7% in a facile label‐free manner. This work guides the development of label‐free cell capture techniques and contributes to the construction of smart interfaces in bio‐systems.     

High‐Performance,Room Temperature,Ultra‐Broadband Photodetectors Based on Air‐Stable PdSe2

Photodetection over a broad spectral range is crucial for optoelectronic applications such as sensing, imaging, and communication. Herein, a high‐performance ultra‐broadband photodetector based on PdSe₂ with unique pentagonal atomic structure is reported. The photodetector responds from visible to mid‐infrared range (up to ≈4.05 µm), and operates stably in ambient and at room temperature. It promises improved applications compared to conventional mid‐infrared photodetectors. The highest responsivity and external quantum efficiency achieved are 708 A W^?1 and 82 700%, respectively, at the wavelength of 1064 nm. Efficient optical absorption beyond 8 µm is observed, indicating that the photodetection range can extend to longer than 4.05 µm. Owing to the low crystalline symmetry of layered PdSe₂, anisotropic properties of the photodetectors are observed. This emerging material shows potential for future infrared optoelectronics and novel devices in which anisotropic properties are desirable.     

Multifunctional “Hydrogel Skins” on Diverse Polymers with Arbitrary Shapes

Slippery and hydrophilic surfaces find critical applications in areas as diverse as biomedical devices, microfluidics, antifouling, and underwater robots. Existing methods to achieve such surfaces rely mostly on grafting hydrophilic polymer brushes or coating hydrogel layers, but these methods suffer from several limitations. Grafted polymer brushes are prone to damage and do not provide sufficient mechanical compliance due to their nanometer‐scale thickness. Hydrogel coatings are applicable only for relatively simple geometries, precluding their use for the surfaces with complex geometries and features. Here, a new method is proposed to interpenetrate hydrophilic polymers into the surface of diverse polymers with arbitrary shapes to form naturally integrated “hydrogel skins.” The hydrogel skins exhibit tissue‐like softness (Young's modulus ≈ 30 kPa), have uniform and tunable thickness in the range of 5–25 µm, and can withstand prolonged shearing forces with no measurable damage. The hydrogel skins also provide superior low‐friction, antifouling, and ionically conductive surfaces to the polymer substrates without compromising their original mechanical properties and geometry. Applications of the hydrogel skins on inner and outer surfaces of various practical polymer devices including medical tubing, Foley catheters, cardiac pacemaker leads, and soft robots on massive scales are further demonstrated.     

Recent advances and an industrial perspective of cellulose nanocrystal functionalization through polymer grafting

Cellulose nanocrystals (CNCs) are an emerging nanomaterial for applications ranging from coatings and construction to adhesives and biomedical devices. Owing to their high aspect ratio, stiffness, and reinforcing potential, CNCs have shown great promise to be used in polymer nanocomposites. However, due to their inherent hydrophilicity and compatibility with polar environments, the use of CNCs in hydrophobic polymer matrices or in organic solvent-based formulations has been limited. To overcome this incompatibility, many reports on grafting polymers onto the surface of CNCs have been published over the past ten years. This review describes the recent advances in CNC surface functionalization through polymer grafting, and comprehensively covers the existing work to date. Methods including polymer “grafting to” and “grafting from” are described in detail, using polymerization techniques such as free radical, ring opening, and controlled radical polymerization. Purification and characterization of polymer-grafted CNCs, the potential for upscaling these functionalization methods, and current perspectives from academic and industrial viewpoints are presented.     

Visually Imperceptible Liquid‐Metal Circuits for Transparent,Stretchable Electronics with Direct Laser Writing

A material architecture and laser‐based microfabrication technique is introduced to produce electrically conductive films (sheet resistance = 2.95 Ω sq^?1; resistivity = 1.77 × 10^?6 Ω m) that are soft, elastic (strain limit >100%), and optically transparent. The films are composed of a grid‐like array of visually imperceptible liquid‐metal (LM) lines on a clear elastomer. Unlike previous efforts in transparent LM circuitry, the current approach enables fully imperceptible electronics that have not only high optical transmittance (>85% at 550 nm) but are also invisible under typical lighting conditions and reading distances. This unique combination of properties is enabled with a laser writing technique that results in LM grid patterns with a line width and pitch as small as 4.5 and 100 µm, respectively—yielding grid‐like wiring that has adequate conductivity for digital functionality but is also well below the threshold for visual perception. The electrical, mechanical, electromechanical, and optomechanical properties of the films are characterized and it is found that high conductivity and transparency are preserved at tensile strains of ≈100%. To demonstrate their effectiveness for emerging applications in transparent displays and sensing electronics, the material architecture is incorporated into a couple of illustrative use cases related to chemical hazard warning.     

An Ultrabroadband Mid‐Infrared Pulsed Optical Switch Employing Solution‐Processed Bismuth Oxyselenide

Pulsed lasers operating in the mid‐infrared (3–25 µm) are increasingly becoming the light source of choice for a wide range of industrial and scientific applications such as spectroscopy, biomedical research, sensing, imaging, and communication. Up to now, one of the factors limiting the mid‐infrared pulsed lasers is the lack of optical switch with a capability of pulse generation, especially for those with wideband response. Here, a semiconductor material of bismuth oxyselenide (Bi₂O₂Se) with a facile processibility, constituting an ultrabroadband saturable absorber for the mid‐infrared (actually from the near‐infrared to mid‐infrared: 0.8–5.0 µm) is exhibited. Significantly, it is found that the optical response is associated with a strong nonlinear character, showing picosecond response time and response amplitude up to ≈330.1% at 5.0 µm. Combined with facile processibility and low cost, these solution‐processed Bi₂O₂Se materials may offer a scalable and printable mid‐infrared optical switch to open up the long‐sought parameter space which is crucial for the exploitation of compact and high‐performance mid‐infrared pulsed laser sources.     

Polymer-Grafted,Gold Nanoparticle-Based Nano-Capsules as Reversible Colorimetric Tensile Strain Sensors

Colloidal colorimetric microsensors enable the in-situ detection of mechanical strains within materials. Enhancing the sensitivity of these sensors to small scale deformation while enabling reversibility of the sensing capability would expand their utility in applications including biosensing and chemical sensing. In this study, we introduce the synthesis of colloidal colorimetric nano-sensors using a simple and readily scalable fabrication method. Colloidal nano sensors are prepared by emulsion-templated assembly of polymer-grafted gold nanoparticles (AuNP). To direct the adsorption of AuNP to the oil-water interface of emulsion droplets, AuNP (≈11nm) are functionalized with thiol-terminated polystyrene (PS, M_n = 11k). These PS-grafted gold nanoparticles are suspended in toluene and subsequently emulsified to form droplets with a diameter of ≈30µm. By evaporating the solvent of the oil-inwater emulsion, we form nanocapsules (AuNC) (diameter < 1µm) decorated by PS-grafted AuNP. To test mechanical sensing, the AuNC are embedded in an elastomer matrix. The addition of a plasticizer reduces the glass transition temperature of the PS brushes, and in turn imparts reversible deformability to the AuNC. The plasmonic peak of the AuNC shifts towards lower wavelengths upon application of uniaxial tensile tension, indicating increased inter-nanoparticle distance, and reverts back as the tension is released.     

Continuous Vat Photopolymerization for Optical Lens Fabrication (Small 40/2023)

Optical lenses require feature resolution and surface roughness that are beyond most (3D) printing methods. A new continuous projection-based vat photopolymerization process is reported that can directly shape polymer materials into optical lenses with microscale dimensional accuracy (< 14.7 µm) and nanoscale surface roughness (< 20 nm) without post-processing. The main idea is to utilize frustum layer stacking, instead of the conventional 2.5D layer stacking, to eliminate staircase aliasing. A continuous change of mask images is achieved using a zooming-focused projection system to generate the desired frustum layer stacking with controlled slant angles. The dynamic control of image size, objective and imaging distances, and light intensity involved in the zooming-focused continuous vat photopolymerization are systematically investigated. The experimental results reveal the effectiveness of the proposed process. The 3D-printed optical lenses with various designs, including parabolic lenses, fisheye lenses, and a laser beam expander, are fabricated with a surface roughness of 3.4 nm without post-processing. The dimensional accuracy and optical performance of the 3D-printed compound parabolic concentrators and fisheye lenses within a few millimeters are investiagted. These results highlight the rapid and precise nature of this novel manufacturing process, demonstrating a promising avenue for future optical component and device fabrication.     

Ultraminiature and Flexible Sensor Based on Interior Corner Flow for Direct Pressure Sensing in Biofluids

Conventional pressure sensing devices are well developed for either indirect evaluation or internal measuring of fluid pressure over millimeter scale. Whereas, specialized pressure sensors that can directly work in various liquid environments at micrometer scale remain challenging and rarely explored, but are of great importance in many biomedical applications. Here, pressure sensor technology that utilizes capillary action to self‐assemble the pressure‐sensitive element is introduced. Sophisticated control of capillary flow, tunable sensitivity to liquid pressure in various mediums, and multiple transduction modes are realized in a polymer device, which is also flexible (thickness of 8 µm), ultraminiature (effective volume of 18 × 100 × 580 µm³), and transparent, enabling the sensor to work in some extreme situations, such as in narrow inner spaces (e.g., a microchannel of 220 µm in width and 100 µm in height), or on the surface of small objects (e.g., a 380 µm diameter needle). Potential applications of this sensor include disposables for in vivo and short‐term measurements.     

High‐Throughput,Protein‐Targeted Biomolecular Detection Using Frequency‐Domain Faraday Rotation Spectroscopy

A clinically relevant magneto‐optical technique (fd‐FRS, frequency‐domain Faraday rotation spectroscopy) for characterizing proteins using antibody‐functionalized magnetic nanoparticles (MNPs) is demonstrated. This technique distinguishes between the Faraday rotation of the solvent, iron oxide core, and functionalization layers of polyethylene glycol polymers (spacer) and model antibody–antigen complexes (anti‐BSA/BSA, bovine serum albumin). A detection sensitivity of ≈10 pg mL^?1 and broad detection range of 10 pg mL^?1 ? c_BSA ? 100 µ g mL^?1 are observed. Combining this technique with predictive analyte binding models quantifies (within an order of magnitude) the number of active binding sites on functionalized MNPs. Comparative enzyme‐linked immunosorbent assay (ELISA) studies are conducted, reproducing the manufacturer advertised BSA ELISA detection limits from 1 ng mL^?1 ? c_BSA ? 500 ng mL^?1. In addition to the increased sensitivity, broader detection range, and similar specificity, fd‐FRS can be conducted in less than ≈30 min, compared to ≈4 h with ELISA. Thus, fd‐FRS is shown to be a sensitive optical technique with potential to become an efficient diagnostic in the chemical and biomolecular sciences.     

Mesoporous Polymeric Cyanamide‐Triazole‐Heptazine Photocatalysts for Highly‐Efficient Water Splitting

Conjugated polymers are promising light harvesters for water reduction/oxidation due to their simple synthesis and adjustable bandgap. Herein, both cyanamide and triazole functional groups are first incorporated into a heptazine‐based carbon nitride (CN) polymer, resulting in a mesoporous conjugated cyanamide‐triazole‐heptazine polymer (CTHP) with different compositions by increasing the quantity of cyanamide/triazole units in the CN backbone. Varying the compositions of CTHP modulates its electronic structures, mesoporous morphologies, and redox energies, resulting in a significantly improved photocatalytic performance for both H₂ and O₂ evolution under visible light irradiation. A remarkable H₂ evolution rate of 12723 µmol h^?1 g^?1 is observed, resulting in a high apparent quantum yield of 11.97% at 400 nm. In parallel, the optimized photocatalyst also exhibits an O₂ evolution rate of 221 µmol h^?1 g^?1, 9.6 times higher than the CN counterpart, with the value being the highest among the reported CN‐based bifunctional photocatalysts. This work provides an efficient molecular engineering approach for the rational design of functional polymeric photocatalysts.     

Laser polishing of aluminum by remelting with high energy pulses

Laser polishing is a contact‐free, quick and automated method to smooth surfaces. The method has been applied to different forging and casting aluminum alloys. The surfaces of the samples were belt‐grinded with a grain size of mesh 240. The samples are protected from ambient air in a gas shield chamber. The used laser system is an Nd : YAG Laser with maximum pulse energy of 65 J. The initial and the laser polished surfaces have been analyzed by microscopy, roughness spectroscopy, white light interferometry and cross‐section polishes. The surfaces of the laser polished forging alloys are covered by multiple lateral and horizontal cracks. Unlike the forging alloys, the casting alloys could be processed well by laser polishing. The initial surface roughness of Ra₂₄₀ = 1.37 µm was reduced up to Ra_LP ≈ 0.47 µm. This represents a roughness reduction of 66%. The roughness spectroscopy of the laser polished surface shows for structural wavelengths from 2.5 µm to 500 µm a Ra‐value close to 0.1 µm and from 500 µm to 800 µm higher values. The remelted area extends up to100 µm into the material.     

Electrostatic Microencapsulation Technique for Producing Composite Particles

The electrostatic microencapsulation process and the various means of achieving such encapsulation for developing composite particles with two or more powders is briefly reviewed, with a particular focus on the dual-function sorbent/scintillation particles for use in radionuclide selective sensing. In preparing the composite particles, two different types of particles, an ion-exchange resin and scintillating microbeads, were used. The sorbent particles capture and preconcentrate the radionuclide of interest (e.g., 99 Tc) from solution. The scintillating microbeads are used to convert the energy of radioactive decay into that detectable light that can be deducted by a photomultiplier tube arrangement. To simulate the electrostatic microencapsulation of resin and scintillators, several surrogate materials such as acrylic powder (mean particle diameter, d 50 =23 µm), red toner (d 50 =16 µm), resin (d 50 =134 µm), and fluorescent latex spheres (d 50 =2 µm) were used. A microencapsulation tower was constructed to use corona guns operating at high voltages of opposite polarity to charge the "host" and "guest" particles. Experimental arrangements and test results are presented. The results show that if polymer particles are used and if one of the two powders is smaller than 10 µm in diameter, the electrostatic and van der Waals forces provide enough interparticle adhesion to bond the guest and host particles through plastic deformation. Interparticles adhesion between resin (d 50 =133 µm) and toner (d 50 =15 µm) showed that the composite particles were stable in water suspension. For larger particles, such as resin and scintillators, the use of a binding agent is necessary to form stable composite particles. electrostatic microencapsulation particle coating groundwater monitoring composite particles radionuclide detection     

聚丙烯酸酯/纳米TiO2复合材料的制备与性能

通过无皂-原位乳液聚合法,以甲基丙烯酸甲酯、丙烯酸丁酯为原料,采用反应性乳化剂1-烯丙氧基-3-(4-壬基苯酚)-2-丙醇聚氧乙烯醚硫酸铵(DNS-86)制备聚丙烯酸酯/纳米TiO2复合材料。采用红外光谱(FT-IR)、动态激光光散射(DLS)、透射电镜(TEM)等检测手段对复合材料的结构进行了表征,通过力学性能、耐水性测试研究了纳米TiO2对复合材料性能的影响。FT-IR测试结果表明纳米TiO2与聚合物发生了相互作用,有少量的TiO2被接枝到聚合物分子中。DLS测试结果表明与纯聚丙烯酸酯相比,聚丙烯酸酯/纳米TiO2复合乳液乳胶粒的平均粒径和粒径分布都有所降低。TEM测试结果表明纳米TiO2分布在聚合物基体中。复合材料的性能测试结果表明,当纳米TiO2的加入量为0.5%时,聚丙烯酸酯/纳米TiO2复合材料的综合力学性能较好;纳米TiO2的加入可提高复合材料的耐水性。     

Functionalized mesoporous silica for microgravimetric sensing of trace chemical vapors

Featuring a huge surface-to-volume ratio, synthesized SBA-15 mesoporous silica is functionalized by inner-channel-wall modification of sensing groups for highly specific chemical-vapor detection at trace level. With the developed sensing material loaded on resonant microcantilevers, the specifically adsorbed chemical-vapor molecules act as an added mass to shift the cantilever resonant frequency for gravimetric sensing signal readout. Two kinds of sensing materials for trinitrotoluene (TNT) and ammonia/amine are respectively prepared by inner-wall layer-by-layer grafting functionalization. By using hexafluoro-2-propanol-functionalized mesoporous silica (HFMS), experimental results show highly specific and rapid detection of TNT vapor, with a ppt-level detection limit; functionalized with a carboxyl (COOH) group, the mesoporous silica is loaded onto the cantilever resonating sensor that experimentally exhibits an ultrafine detection limit of tens of ppb to ammonia/amine gases.     

Flexible Nanoarchitectonics for Biosensing and Physiological Monitoring Applications

Flexible and implantable electronics hold tremendous promises for advanced healthcare applications, especially for physiological neural recording and modulations. Key requirements in neural interfaces include miniature dimensions for spatial physiological mapping and low impedance for recognizing small biopotential signals. Herein, a bottom-up mesoporous formation technique and a top-down microlithography process are integrated to create flexible and low-impedance mesoporous gold (Au) electrodes for biosensing and bioimplant applications. The mesoporous architectures developed on a thin and soft polymeric substrate provide excellent mechanical flexibility and stable electrical characteristics capable of sustaining multiple bending cycles. The large surface areas formed within the mesoporous network allow for high current density transfer in standard electrolytes, highly suitable for biological sensing applications as demonstrated in glucose sensors with an excellent detection limit of 1.95 µm and high sensitivity of 6.1 mA cm⁻² µM⁻¹, which is approximately six times higher than that of benchmarking flat/non-porous films. The low impedance of less than 1 kΩ at 1 kHz in the as-synthesized mesoporous electrodes, along with their mechanical flexibility and durability, offer peripheral nerve recording functionalities that are successfully demonstrated in vivo. These features highlight the new possibilities of our novel flexible nanoarchitectonics for neuronal recording and modulation applications.     

Ultra-Short Pulsed Laser Manufacturing and Surface Processing of Microdevices

Ultra-short laser pulses possess many advantages for materials processing. Ultrafast laser has a significantly low thermal effect on the areas surrounding the focal point; therefore, it is a promising tool for micro- and submicro-sized precision processing. In addition, the nonlinear multiphoton absorption phenomenon of focused ultra-short pulses provides a promising method for the fabrication of various structures on transparent material, such as glass and transparent polymers. A laser direct writing process was applied in the fabrication of high-performance three-dimensional (3D) structured multilayer micro-supercapacitors (MSCs) on polymer substrates exhibiting a peak specific capacitance of 42.6 mF·cm⁻² at a current density of 0.1 mA·cm⁻². Furthermore, a flexible smart sensor array on a polymer substrate was fabricated for multi-flavor detection. Different surface treatments such as gold plating, reduced-graphene oxide (rGO) coating, and polyaniline (PANI) coating were accomplished for different measurement units. By applying principal component analysis (PCA), this sensing system showed a promising result for flavor detection. In addition, two-dimensional (2D) periodic metal nanostructures inside 3D glass microfluidic channels were developed by all-femtosecond-laser processing for real-time surface-enhanced Raman spectroscopy (SERS). The processing mechanisms included laser ablation, laser reduction, and laser-induced surface nano-engineering. These works demonstrate the attractive potential of ultra-short pulsed laser for surface precision manufacturing.     

生物基可降解聚合物食品包装材料发展及应用综述

目的 介绍生物基聚合物包装的研究进展，总结生物基聚合物包装材料的功能化。方法 综述目前生物基聚合物包装材料来源的分类，列举天然生物基聚合物、微生物合成的生物基聚合物和化学合成的生物基聚合物在食品包装方面的研究进展，总结生物基聚合物包装材料的功能化方向(抗菌、抗氧化、pH响应、光热响应等)。结论 生物基聚合物食品包装在绿色食品包装领域有较好的应用潜力。     

Microcontact Printing with Laser Direct Writing Carbonization for Facile Fabrication of Carbon‐Based Ultrathin Disk Arrays and Ordered Holey Films

A nanometer‐thick carbon film with a highly ordered pattern structure is very useful in a variety of applications. However, its large‐scale, high‐throughput, and low‐cost fabrication is still a great challenge. Herein, microcontact printing (µCP) and direct laser writing carbonization (DLWc) are combined to develop a novel method that enables ease of fabrication of nanometer‐thick and regularly patterned carbon disk arrays (CDAs) and holey carbon films (HCFs) from a pyromellitic dianhydride‐oxydianiline‐based polyamic acid (PAA) solution. The effect of PAA concentration and pillar lattice structure of the polydimethyl siloxane stamp are systematically studied for their influence on the geometrical parameter, surface morphology, and chemical structure of the finally achieved CDAs and HCFs. Within the PAA concentration being investigated, the averaged thickness of CDAs and HCFs can be tailored in a range from a few tens to a few hundred of nanometers. The µCP+DLWc‐enabled electrically conductive CDAs and HCFs possess the characteristics of ease‐of‐fabrication, nanometer‐thickness, highly regular and controlled patterns and structures, and the ability to form on both hard and soft substrates, which imparts usefulness in electronics, photonics, energy storage, catalysis, tissue engineering, as well as physical, chemical, and bio‐sensing applications.     

聚硅氧烷型交联剂的制备及其在聚合物多孔材料中的应用

为了获得性能优异的聚合物多孔材料,首先,在封端剂六甲基二硅氧烷(MM)的存在下,通过硅酸钠与甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)的水解缩聚反应制备了含甲基丙烯酰氧基丙基官能基团的MTQ有机硅树脂;然后,以MTQ硅树脂为交联剂,丙烯酸异辛酯(EHA)为单体,利用高内相比乳液模板法制备了MTQ硅树脂/聚丙烯酸异辛酯(PEHA)聚合物多孔材料;最后,对该多孔材料的孔结构、压缩性能和热稳定性进行了研究。结果表明:采用MTQ硅树脂作为交联剂制备得到的MTQ硅树脂/PEHA聚合物多孔材料的泡孔孔径介于4~10μm范围内,毛孔孔径分布于0.3~2.0μm区间内;泡孔之间紧密相连,毛孔均匀分布且通道较窄。MTQ硅树脂含量对MTQ硅树脂/PEHA聚合物多孔材料的比表面积和孔容的影响较小,但可显著提高聚合物多孔材料的热稳定性和压缩强度;在氮气氛围下,聚合物多孔材料的最大热分解速率温度可达411.5℃。