Printing Of Arrays Research Articles

Nanograting-Based Dynamic Structural Colors Using Heterogeneous Materials

AbstractDynamic structural colors can change in response to different environmental stimuli. This ability remains effective even when the size of the species responsible for the structural color is reduced to a few micrometers, providing a promising sensing mechanism for solving microenvironmental sensing problems in micro-robotics and microfluidics. However, the lack of dynamic structural colors that can encode rapidly, easily integrate, and accurately reflect changes in physical quantities hinders their use in microscale sensing applications. Herein, we present a 2.5-dimensional dynamic structural color based on nanogratings of heterogeneous materials, which were obtained by interweaving a pH-responsive hydrogel with an IP-L photoresist. Transverse gratings printed with pH-responsive hydrogels elongated the period of longitudinal grating in the swollen state, resulting in pH-tuned structural colors at a 45° incidence. Moreover, the patterned encoding and array printing of dynamic structural colors were achieved using grayscale stripe images to accurately encode the periods and heights of the nanogrid structures. Overall, dynamic structural color networks exhibit promising potential for applications in information encryption and in situ sensing for microfluidic chips.

Preparation of high-resolution micro/nano dot array by electrohydrodynamic jet printing with enhanced uniformity

The high-resolution array is the basic structure of most kinds of microelectronics. Electrohydrodynamic jet (E-Jet) printing technology is widely applied in manufacturing array structures with high resolution, high material compatibility and multi-modal printing. It is still challenging to acquire high uniformity of printed array with micro-nanometer resolution, which greatly influences the performance and lifetime of the microelectronics. In this paper, to improve the uniformity of the printed array, the influence of each parameter on the uniformity of the E-jet printed dot array is studied on the cobuilt NEJ-E/P200 experimental platform, finding the applied voltage plays the most important role in maintaining the uniformity of the printed array. By appropriately adjusting the printing parameters, the dot arrays with different resolutions from 500 pixels per inch (PPI) to 17,000 PPI are successfully printed. For arrays below and over 10,000 PPI, the deviations of the uniformity are within 5% and 10% respectively. In this work, the dot array over 15,000 PPI is first implemented using E-jet printing. The conclusions acquired by experimental analysis of dot array printing process are of great importance in high resolution array printing as it provides practical guidance for parameters adjustment.

Inkjet printing of pixel arrays: droplet formation and pattern uniformity of a non-aqueous ink with tunable viscosity

Inkjet printing is a rapid and material-efficient process that is suitable for the fabrication of large-area microarrays from a range of optoelectronic materials. In order to ensure stable droplet formation and a uniform print image with very smooth surfaces, however, the ink properties such as viscosity and surface tension have to be precisely adjusted. In this study, a non-aqueous ink formulation is proposed whose viscosity can be conveniently adjusted by controlling the mixing ratio of propylene carbonate (PC) as the low-viscosity solvent and propylene glycol (PG) as the high-viscosity solvent. Using a combination of advanced imaging techniques, we show that raising the PG content from 20% to 80% increased the viscosity of the ink from 3.36 cP to 26.70 cP, resulting in stable droplet formation and a more evenly printed image. At a spacing of 5 dots/pixel, the roughness value decreased dramatically, from root mean square (RMS): 11.28 (20% PG) to RMS: 0.09 (80% PG). Alternatively, more homogeneous patterns (albeit with a rough surface) were also produced with the low-viscosity ink (20% PG) when a conditioned substrate with low surface energy and selective liquid repellency was used. With this we present a simple but effective strategy to improve droplet formation while obtaining highly uniform pixel arrays. The knowledge gained will be particularly useful for inkjet printing of pixel-patterned color conversion layers in devices such as organic light-emitting diodes (LEDs) and micro-LED displays.

Researching and Predicting the Flow Distribution of Herschel-Bulkley Fluids in Compact Parallel Channels

There is growing interest in multi-nozzle array printing, as it has the potential to increase productivity and produce more intricate products. However, a key challenge is ensuring consistent flow across each outlet. In the heat exchangers, achieving uniform distribution of flow in parallel channels is a classic goal. To address this issue in multi-nozzle array direct printing technology, high-viscosity slurry fluids can be utilized in place of water, and the structure of compact parallel channels can be employed. This study experimentally and numerically investigated the flow distribution law of Herschel-Bulkley fluids (high-viscosity slurry fluids) entering each manifold of the compact parallel channels, which contained a single circular inlet and multiple outlets. The research identified two types of factors that impact the non-uniformity flow coefficient (Φ), which reflects the uniformity of flow distribution in each channel of the structure: entrance and exit conditions (V, P1, P2) that have a negligible effect on Φ, and structural dimensions (D, S, L, N, A, d) that are the primary influence factors. By analyzing the experimental results, a prediction model was derived that could accurately calculate Φ (error < 0.05) based on three structural dimensions: A, S, and L. Through proper design of these structural dimensions, a consistent flow rate of each channel of the parallel channels can be ensured.

3D-Printed Microinjection Needle Arrays via a Hybrid DLP-Direct Laser Writing Strategy.

Microinjection protocols are ubiquitous throughout biomedical fields, with hollow microneedle arrays (MNAs) offering distinctive benefits in both research and clinical settings. Unfortunately, manufacturing-associated barriers remain a critical impediment to emerging applications that demand high-density arrays of hollow, high-aspect-ratio microneedles. To address such challenges, here, a hybrid additive manufacturing approach that combines digital light processing (DLP) 3D printing with "ex situ direct laser writing (esDLW)" is presented to enable new classes of MNAs for fluidic microinjections. Experimental results for esDLW-based 3D printing of arrays of high-aspect-ratio microneedles-with 30 μm inner diameters, 50 μm outer diameters, and 550 μm heights, and arrayed with 100 μm needle-to-needle spacing-directly onto DLP-printed capillaries reveal uncompromised fluidic integrity at the MNA-capillary interface during microfluidic cyclic burst-pressure testing for input pressures in excess of 250 kPa (n = 100 cycles). Ex vivo experiments perform using excised mouse brains reveal that the MNAs not only physically withstand penetration into and retraction from brain tissue but also yield effective and distributed microinjection of surrogate fluids and nanoparticle suspensions directly into the brains. In combination, the results suggest that the presented strategy for fabricating high-aspect-ratio, high-density, hollow MNAs could hold unique promise for biomedical microinjection applications.

3D printing of microneedle arrays for hair regeneration in a controllable region

Hair loss is a common skin disease that causes intense emotional suffering. Hair regeneration in a personalized area is highly desirable for patients with different balding conditions. However, the existing pharmaceutical treatments have difficulty precisely regenerating hair in a desired area. Here, we show a method to precisely control the hair regeneration using customized microneedle arrays (MNAs). The MNA with a customized shape is fast fabricated by a static optical projection lithography process in seconds, which is a 3D printing technology developed by our group. In the mouse model, MNA treatment could induce hair regrowth in a defined area corresponding to the customized shape of MNA. And the regenerated hair promoted by MNAs had improved quality. Cellular and molecular analysis indicated that MNA treatment could recruit macrophages in situ and then initiate the proliferation of hair follicle stem cells, thereby improving hair regeneration. Meanwhile, the activation of the Wnt/β-catenin signaling pathway was observed in hair follicles. The expressions of Hgf, Igf 1 and Tnf-α were also upregulated in the treated skin, which may also be beneficial for the MNA-induced hair regeneration. This study provides a strategy to precisely control hair regeneration using customized microneedle arrays by recruiting macrophages in situ, which holds the promise for the personalized treatment of hair loss.

A liquid-free conducting ionoelastomer for 3D printable multifunctional self-healing electronic skin with tactile sensing capabilities.

Conductive elastomers with both softness and conductivity are widely used in the field of flexible electronics. Nonetheless, conductive elastomers typically exhibit prominent problems such as solvent volatilization and leakage, and poor mechanical and conductive properties, which limit their applications in electronic skin (e-skin). In this work, a liquid-free conductive ionogel (LFCIg) with excellent performance was fabricated by utilizing the innovative double network design approach based on a deep eutectic solvent (DES). The double-network LFCIg is cross-linked by dynamic non-covalent bonds, which exhibit excellent mechanical properties (2100% strain while sustaining a fracture strength of 1.23 MPa) and >90% self-healing efficiency, and a superb electrical conductivity of 23.3 mS m-1 and 3D printability. Moreover, the conductive elastomer based on LFCIg has been developed into a stretchable strain sensor that achieves accurate response recognition, classification, and identification of different robot gestures. More impressively, an e-skin with tactile sensing functions is produced by in situ 3D printing of sensor arrays on flexible electrodes to detect light weight objects and recognize the resulting spatial pressure variations. Collectively, the results demonstrate that the designed LFCIg has unparalleled advantages and presents wide application potential in flexible robotics, e-skin and physiological signal monitoring.

Controlling the Surface Modification by CF4 Plasma Treatment for Inkjet Printed Color Conversion Layer With InP‐Based QDs Ink

AbstractControlling of thickness profile in micro‐scale pixels via an inkjet printing process remains a challenge and strict control of surface energy is required. Herein, the surface energy of each substrate is controlled by using CF4 plasma treatment (CPT) to control thickness profile and improve color conversion efficiency (CCE) of the inkjet printed quantum dots (QDs) color conversion layer (CCL). The bank surface becomes hydrophobic due to the fluorination, while the glass becomes hydrophilic due to the cleaning effect by the CPT. Through a systemic investigation of the polar and non‐polar components of the surface energy, it is found that the ink behavior of inkjet‐printed QDs in the pixels is closely related to the non‐polar component of the surface energy. In addition, it is found that more rigorous control of the surface is required for array printing and a wide range of thickness profile control is possible by CPT. The thickness increases by up to 10 µm, the blue leakage is reduced by 26.38%, and the CCE increases by a maximum of 5.71% depending on the CPT. As a result, the relationship between the thickness profile of the CCL and CCE is confirmed through the fabrication of QD‐organic light emitting diodes.

3D Meniscus‐Guided Evaporative Assembly for Rapid Template‐Free Synthesis of Highly Crystalline Perovskite Nanowire Arrays

AbstractLow‐dimensional nanostructures of halide perovskites have been receiving extensive research interest for their superior optical, electrical, and stability characteristics over their conventional bulk counterparts. In particular, the unique surficial characteristics of well‐defined 1D nanowires have shown high feasibility for high performance optoelectronic applications. The key aspect of endorsing this nanoscale form factor in practical applications lies in securing dimensional uniformity and controllability in large scales, which generally requires complicated lithographic procedures. In this work, a simple, rapid, and widely applicable strategy for the direct synthesis and printing of well‐aligned nanowire arrays on a large scale is demonstrated. By employing blade coating methods with sophisticatedly controlled stick‐slip motions, periodically resolved transverse 3D meniscus enables uniform directional growth of highly crystalline CsPbI3 nanowires without the need for templates. A systematic investigation of morphological evolutions with respect to kinetic processing variables is conducted, along with a comprehensive suite of structural and optical analyses for the synthesized nanowire arrays. A single nanowire photodetector is employed to demonstrate the superiority and applicability of the fabrication strategy. Finally, a 2D image recognition is demonstrated by using an array of photodetectors fabricated via a fast (<2 min) direct printing of nanowire arrays on wafers.

A REVIEW ON PRESENT AND FUTURE OUTLOOK OF 3D PRINTING IN TRANSDERMAL DRUG DELIVERY SYSTEMS

The suitability of different printing processes for the direct or indirect printing of microneedle arrays, as well as the modification of their surface with drug-containing coatings, has been investigated. 3D printing refers to a group of technologies that use numerically controlled apparatus to create a physical object from a virtual representation. The transdermal route has been introduced as an alternative to the bolus system. The skin is also identified to pose a barrier to permit molecules. The loss that occurred is compensated by transdermal delivery. 3D printing has several advantages in terms of waste reduction, design flexibility, and lowering the high cost. The compatibility of 3D printing techniques with printed medicine products is a factor in their selection. The variety of printable materials that are presently being used or could be utilized for 3D printing of transdermal drug delivery (TDD) devices. 3D printing has the potential to change today's "one size fits all" production and be used across the medication development process. 3D printing technology in the field of transdermal drug development as the system can be advanced in such as way that concentration can be increased or decreased with various drugs used in the printed featuring layers to enhancement of therapeutic efficacy. The impact and limitations of using 3D printing as a production process for transdermal drug delivery devices are required to be evaluated. This review discusses the present and future overlook of 3D printing technology of transdermal drug delivery systems and some advantages and disadvantages of 3D printing technology over conventional drug delivery approach.

3D-Printed Microneedles for Point-of-Care Biosensing Applications.

Microneedles (MNs) are an emerging technology for user-friendly and minimally invasive injection, offering less pain and lower tissue damage in comparison to conventional needles. With their ability to extract body fluids, MNs are among the convenient candidates for developing biosensing setups, where target molecules/biomarkers are detected by the biosensor using the sample collected with the MNs. Herein, we discuss the 3D printing of microneedle arrays (MNAs) toward enabling point-of-care (POC) biosensing applications.

3D Printing of Microneedle Arrays: Challenges Towards Clinical Translation

3D Printing of Microneedle Arrays: Challenges Towards Clinical Translation

Fabrication of Perovskite Solar Cells with Digital Control of Transparency by Inkjet Printing.

Semitransparency is an attractive and important property in solar cells since it opens new possibilities in a variety of applications such as tandem cell configuration and building-integrated photovoltaics. Metal halide perovskite has the optimal properties to function as the light harvester in solar cells and can be made as a thin film, while its chemical composition can change its band gap. However, achieving high transparency usually compromises the solar cell's efficiency. Here we report on a unique approach to fabricating semitransparent perovskite solar cells that does not rely on their composition or their thickness. The approach is based on a scalable process, inkjet printing of arrays of transparent pillars, which are composed of inert photopolymerizable liquid compositions and are partly covered by the perovskite. This material can be printed at specific locations and array densities, thus providing a digital control of both the transparency and efficiency of the solar cells. The new semitransparent device structure shows 11.2% efficiency with 24% average transparency without a top metal contact. Further development including deposition of a transparent contact enabled the fabrication of fully semitransparent devices with an efficiency of 10.6% and average transparency of 19%.

Three-dimensional nanoprinting via charged aerosol jets.

Three-dimensional (3D) printing1-9 has revolutionized manufacturing processes for electronics10-12, optics13-15, energy16,17, robotics18, bioengineering19-21 and sensing22. Downscaling 3D printing23 will enable applications that take advantage of the properties of micro- and nanostructures24,25. However, existing techniques for 3D nanoprinting of metals require a polymer-metal mixture, metallic salts or rheological inks, limiting the choice of material and the purity of the resulting structures. Aerosol lithography has previously been used to assemble arrays of high-purity 3D metal nanostructures on a prepatterned substrate26,27, but in limited geometries26-30. Here we introduce a technique for direct 3D printing of arrays of metal nanostructures with flexible geometry and feature sizes down to hundreds of nanometres, using various materials. The printing process occurs in a dry atmosphere, without the need for polymers or inks. Instead, ions and charged aerosol particles are directed onto a dielectric mask containing an array of holes that floats over a biased silicon substrate. The ions accumulate around each hole, generating electrostatic lenses that focus the charged aerosol particles into nanoscale jets. These jets are guided by converged electric-field lines that form under the hole-containing mask, which acts similarly to the nozzle of a conventional 3D printer, enabling 3D printing of aerosol particles onto the silicon substrate. By moving the substrate during printing, we successfully print various 3D structures, including helices, overhanging nanopillars, rings and letters. In addition, to demonstrate the potential applications of our technique, we printed an array of vertical split-ring resonator structures. In combination with other 3D-printing methods, we expect our 3D-nanoprinting technique to enable substantial advances in nanofabrication.

Flexible ferroelectric wearable devices for medical applications.

SummaryWearable electronics are becoming increasingly important for medical applications as they have revolutionized the way physiological parameters are monitored. Ferroelectric materials show spontaneous polarization below the Curie temperature, which changes with electric field, temperature, and mechanical deformation. Therefore, they have been widely used in sensor and actuator applications. In addition, these materials can be used for conversion of human-body energy into electricity for powering wearable electronics. In this paper, we review the recent advances in flexible ferroelectric materials for wearable human energy harvesting and sensing. To meet the performance requirements for medical applications, the most suitable materials and manufacturing techniques are reviewed. The approaches used to enhance performance and achieve long-term sustainability and multi-functionality by integrating other active sensing mechanisms (e.g. triboelectric and piezoresistive effects) are discussed. Data processing and transmission as well as the contribution of wearable piezoelectric devices in early disease detection and monitoring vital signs are reviewed.

Protein microarrays: The future of allergy diagnosis? Optimization of coating and printing of allergen arrays used with fluorescent humanised basophil reporter cell line NFAT-DsRed RBL

Up-to-date, in vitro allergy diagnosis techniques rely on the detection of allergen-specific Immunoglobulin E (sIgE). Protein microarrays enable the simultaneous screening of hundreds of sIgEs using only a small amount of serum. However, they do not always report clinically relevant sIgE. Combining protein arrays with humanised rat basophilic leukaemia (RBL) reporter cells that provide a biological readout, we aim to develop a high-throughput amenable, clinically relevant allergy diagnosis platform. Here, we demonstrate the effectiveness of different extracellular matrix (ECM) proteins to facilitate RBL cell attachment on various polymer-coated slide surfaces. We also determine printed protein stability using time-of flight secondary ion mass spectrometry (ToF-SIMS). Lastly, we demonstrate the ability of this system to detect an allergic response. Aldehyde-, epoxy- and amine-coated glass slides were coated with 10 μg/mL vitronectin, fibronectin or laminin for 48 hours at 37 ͦ C and with 10 μg/mL collagen for 48 hours at 4 ͦ C. After incubation, NFAT-DsRed RBL cells were cultured on each surface for 72 hours. The number of adherent cells was assessed every 24 hours using 1 μg/mL Hoechst 33342 solution. Next, the following proteins diluted in PBS to a final concentration of 1mg/mL, goat anti-human IgE, timothy grass pollen extract, human serum albumin, k-casein from bovine milk or the above mentioned proteins diluted with 10% fibronectin, were printed in triplicate onto the different polymer-coated slides using a XYZ3200 dispensing workstation (Biodot). Printed proteins were characterized by ToF-SIMS before and after washing the surfaces with deionized water. Finally, cells were sensitized overnight with human IgE. Cell activation was assessed using fluorescence microscopy after 24h incubation onto the protein printed surfaces. Treatment of the aldehyde- and epoxy-coated slides with different ECM proteins had no significant effect on cell adhesion compared to control (cells only). The amine coated surfaces showed higher printed protein stability compared to aldehyde and epoxy ones. Lastly, cell activation was higher on the epoxy slides after printing 10% fibronectin containing protein solution compared to control (protein only). The epoxy-coated slides would consist the optimum platform to assess cell activation and potentially detect an allergic response.

Using the Patterned Microarray Culture to Obtain Gene-Editing Monoclonal Cells

Genetically modified pigs are the first choice for xenotransplantation research, but there have been problems with monoclonal screening of edited cells before nuclear transfer. Our objective was to get a novel strategy to quickly obtain monoclonal cells with low damage by microarray and to produce efficient gene-editing monoclonal cells in batches. Micropattern array printing technology was introduced to limit only a single cell was adhered on a micropattern substrate, and after 4 days of culture, the single cell grew into a monoclonal cell sphere and then came off from the bottom of the petri dish automatically. After sequencing, the results showed that a single cell is confined to a micropattern and grows into a sphere of monoclonal cells.

Retarded Charge–Carrier Recombination in Photoelectrochemical Cells from Plasmon‐Induced Resonance Energy Transfer

AbstractN‐type metal oxides such as hematite (α‐Fe2O3) and bismuth vanadate (BiVO4) are promising candidate materials for efficient photoelectrochemical water splitting; however, their short minority carrier diffusion length and restricted carrier lifetime result in undesired rapid charge recombination. Herein, a 2D arranged globular Au nanosphere (NS) monolayer array with a highly ordered hexagonal hole pattern (hereafter, Au array) is introduced onto the surface of photoanodes comprised of metal oxide films via a facile drying and transfer‐printing process. Through plasmon‐induced resonance energy transfer, the Au array provides a strong electromagnetic field in the near‐surface area of the metal oxide film. The near‐field coupling interaction and amplification of the electromagnetic field suppress the charge recombination with long‐lived photogenerated holes and simultaneously enhance the light harvesting and charge transfer efficiencies. Consequently, an over 3.3‐fold higher photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) is achieved for the Au array/α‐Fe2O3. Furthermore, the high versatility of this transfer printing of Au arrays is demonstrated by introducing it on the molybdenum‐doped BiVO4 film, resulting in 1.5‐fold higher photocurrent density at 1.23 V versus RHE. The tailored metal film design can provide a potential strategy for the versatile application in various light‐mediated energy conversion and optoelectronic devices.

Efficient generation of arrays of closed-packed high-quality light rings

Recently, structured laser beams are gaining attention in laser–matter interactions and related applications of metamaterials and metasurfaces. Ablative laser printing using ultrashort, femto- or picosecond, structured laser pulses allows the large-scale, high-throughput, single-step fabrication of surface nano- or microelement arrays. In this paper, for the purpose of laser printing of arrays of micro and nanoring structures, we investigate the generation of closed-packed light rings with a minimum possible diameter using a combination of a light ring distribution generator and a diffractive beam splitter. As a light ring distribution generator, we use the well-known S-waveplate and generate three different types of ring-shaped laser beams: an azimuthally polarized Gaussian beam, a first-order circularly polarized optical vortex beam, and a first-order linearly polarized optical vortex beam. Our modeling and experimental results show that the azimuthally polarized Gaussian beam is the best solution for splitting in comparison with the other types of beams.

Large-Area Nanopatterning Based on Field Alignment by the Microscale Metal Mask for the Etching Process.

Recently, researchers have dedicated efforts toward producing large-area nanostructures using advanced lithography techniques and state-of-the-art etching methods. However, these processes involve challenges such as the diffraction limit and an unintended etching profile. In this work, we demonstrate large-area nanopatterning on a silicon substrate using the microscale metal mask by meticulous optimization of the etching process. Around the vertex of a microscale metal mask, a locally induced electric field is generated by a bias voltage applied on a silicon mold. We utilize this field to change the trajectory of reactive ions and their effect flux, thus providing a controllable bowing effect. The results are analyzed by both numerical simulations and experiments. Based on the field alignment by the metal mask for the etching (FAME) process, we demonstrate the fabrication of 378 nm-size nanostructure patterns which translate to a size reduction of 63% from 1 μm-size mask patterns on a wafer by optimization of the processes. This is much higher than the undercut (∼37%) usually achieved by a typical non-Bosch process under similar etching conditions. The optimized nanostructure is used as a mold for the transfer printing of nanostructure arrays on a flexible substrate to demonstrate that it enables the functionality of FAME-processed nanostructures.