Direct-write Technology Research Articles

A rapid diagnostic test for human Visceral Leishmaniasis using novel Leishmania antigens in a Laser Direct-Write Lateral Flow Device

ABSTRACT Visceral Leishmaniasis (VL) causes high morbidity and mortality in low-to-middle-income countries worldwide. In this study, we used Laser Direct-Write (LDW) technology to develop a new Lateral Flow Device (LFD) with double-channel geometry on a low-cost paper platform as a rapid and accurate serodiagnostic assay for human VL. This Duplex VL-LFD was based on a laser-patterned microfluidic device using two recombinant Leishmania proteins, β-tubulin and LiHyp1, as novel diagnostic antigens. The VL-LFD assay was tested with blood/serum samples from patients diagnosed with VL, Tegumentary Leishmaniasis, Leishmaniasis of unknown identity, other parasitic diseases with similar clinical symptoms, i.e. Leprosy Disease and Chagas Disease, and blood from healthy donors, and compared in parallel with commercial rK39 IT-LEISH® Kit. Clinical diagnosis and real-time Polymerase Chain Reaction assay were used as reference standards. VL-LFD Sensitivity (S ± 95% Confidence Intervals (CI)) of 90.9 (78.9-100) and Specificity (Sp ± 95% CI) of 98.7 (96.1-100) outperformed the IT-LEISH® Kit [S = 77.3 (59.8-94.8), Sp = 94.7 (89.6-99.8)]. This is the first study reporting successful development of an LFD assay using the LDW technology and the VL-LFD warrants comparative testing in larger patient cohorts and in areas with endemic VL in order to improve diagnosis and disease management.

Direct Write Fabrication of Platinum-Based Thick-Film Resistive Temperature Detectors

This paper investigates the feasibility and performance of platinum thick-film resistance temperature detectors (RTDs) fabricated using extrusion-based direct write (DW). A platinum (Pt) layer of micron-level thickness was directly deposited onto a planar alumina substrate and was physically and electrically characterized. A four-wire electrical configuration was used to eliminate the effects of contact resistance and increase measurement accuracy. The resistance-temperature behavior of printed Pt traces was consistent with that of bulk Pt wire. Durability testing indicated the printed Pt RTD was suitable for temperature measurements from room temperature to at least 350 °C, showing no degradation under long-term heating and lower signal noise than was observed in a Nickel-alloy type E thermocouple (TC). At 500 °C, the peak temperature variation of the Pt RTD was comparable to that of the type E TCs. To demonstrate the design freedom enabled by DW technology, an additional conformal RTD design was deposited onto a semi-cylinder glass-ceramic substrate and was subsequently characterized. This paper offers an alternative to current thick-film RTD fabrication techniques.

Fabrication and evaluation of controllable deposition distance for aligned pattern by multi-nozzle near-field electrospinning

To mass-volume fabricate micro- and nano-scales aligned pattern, multi-nozzle near-field electrospinning (NFES) direct-writing technology is well proposed as a high-efficiency method in electrohydrodynamic (EHD) printing process. However, the interference effect among adjacent nozzles and coupling effect of various parameters have restricted to investigate deposition characteristic of multi-nozzle NFES and control EHD multi-jet deposition accuracy. In order to improve the accuracy of EHD multi-jet deposition with high-efficiency printing process, the experimental result compared with theoretical method were discussed. In this work, the influence of multi-nozzle geometry distribution and electrospinning parameters on deposition characteristic was studied with multi-nozzle NFES setup, and nozzles were in linear array. The deposition distance and homogeneity of aligned nanofibers were measured and explained with coefficient of dispersion on electric field among nozzles by simulation. Moreover, deposition distance of multi-nozzle NFES process was evaluated by modified theoretical derivation based on our previous studies. The modified theoretical derivation showed a good agreement with experiment results, and indicated that multi-nozzle NFES could accurately and efficiently direct-write aligned array pattern in future.

Alternative Technology for Creating Nanostructures Using Dip Pen Nanolithography

For modern microelectronics, at the present time, the technologies of consciousness smart structures play an important role, which can provide accuracy, stability and high quality of the structures. Submicron lithography methods are quite expensive and have natural size limitations, not allowing the production of structures with an extremely small lateral limitation. Therefore, an intensive search was conducted for alternative methods for creating submicron resolution structures. Especially attractive one is the possibility of self-organization effects utilization, where the nanostructure of a certain size is formed under the influence of internal forces. The dip pen nanolithography method based on a scanning probe microscope uses a directwrite technology and allows one to carry out a playback of small size structures with high accuracy. In the experiment, a substrate coated with Au (15 nm) using a DPN technique is applied to the polymer to form a desired pattern nano-sized channel. The experiment was conducted using a pointed probe SiN, coated MHA-Acetonitrile, on the Si(111)/Fe3Si/Au structure.

Large-Scale Direct-Writing of Aligned Nanofibers for Flexible Electronics.

Nanofibers/nanowires usually exhibit exceptionally low flexural rigidities and remarkable tolerance against mechanical bending, showing superior advantages in flexible electronics applications. Electrospinning is regarded as a powerful process for this 1D nanostructure; however, it can only be able to produce chaotic fibers that are incompatible with the well-patterned microstructures in flexible electronics. Electro-hydrodynamic (EHD) direct-writing technology enables large-scale deposition of highly aligned nanofibers in an additive, noncontact, real-time adjustment, and individual control manner on rigid or flexible, planar or curved substrates, making it rather attractive in the fabrication of flexible electronics. In this Review, the ground-breaking research progress in the field of EHD direct-writing technology is summarized, including a brief chronology of EHD direct-writing techniques, basic principles and alignment strategies, and applications in flexible electronics. Finally, future prospects are suggested to advance flexible electronics based on orderly arranged EHD direct-written fibers. This technology overcomes the limitations of the resolution of fabrication and viscosity of ink of conventional inkjet printing, and represents major advances in manufacturing of flexible electronics.

High-Fidelity 3D-Nanoprinting via Focused Electron Beams: Growth Fundamentals

While 3D-printing is currently experiencing significant growth and having a significant impact on science and technology, the expansion into the nanoworld is still a highly challenging task. Among the increasing number of approaches, focused electron-beam-induced deposition (FEBID) was recently demonstrated to be a viable candidate toward a generic direct-write fabrication technology with spatial nanometer accuracy for complex shaped 3D-nanoarchitectures. In this comprehensive study, we explore the parameter space for 3D-FEBID and investigate the implications of individual and interdependent parameters on freestanding nanosegments, which act as a fundamental building block for complex 3D-structures. In particular, the study provides new basic insights such as precursor transport limitations and angle dependent growth rates, both essential for high-fidelity fabrication. Complemented by practical aspects, we provide both basic insights in 3D-growth dynamics and technical guidance for specific process adapti...

Alternative technology for creating nanostructures using Dip Pen Nanolithography

AbstractFor modern microelectronics, at the present time, the technologies of consciousness smart structures play an important role, which can provide accuracy, stability and high quality of the structures. Submicron lithography methods are quite expensive and have natural size limitations, not allowing the production of structures with an extremely small lateral limitation. Therefore, an intensive search was conducted for alternative methods for creating submicron resolution structures. Especially attractive one is the possibility of self-organization effects utilization, where the nanostructure of a certain size is formed under the influence of internal forces. The dip pen nanolithography method based on a scanning probe microscope uses a directwrite technology and allows one to carry out a playback of small size structures with high accuracy. In the experiment, a substrate coated with Au (15 nm) using a DPN technique is applied to the polymer to form a desired pattern nano-sized channel. The experiment was conducted using a pointed probe SiN, coated MHA-Acetonitrile, on the Si(111)/Fe_3Si/Au structure.

Additive direct-write microfabrication for MEMS: A review

Direct-write additive manufacturing refers to a rich and growing repertoire of well-established fabrication techniques that builds solid objects directly from computer- generated solid models without elaborate intermediate fabrication steps. At the macroscale, direct-write techniques such as stereolithography, selective laser sintering, fused deposition modeling ink-jet printing, and laminated object manufacturing have significantly reduced concept-to-product lead time, enabled complex geometries, and importantly, has led to the renaissance in fabrication known as the maker movement. The technological premises of all direct-write additive manufacturing are identical—converting computer generated three-dimensional models into layers of two-dimensional planes or slices, which are then reconstructed sequentially into threedimensional solid objects in a layer-by-layer format. The key differences between the various additive manufacturing techniques are the means of creating the finished layers and the ancillary processes that accompany them. While still at its infancy, direct-write additive manufacturing techniques at the microscale have the potential to significantly lower the barrier-of-entry—in terms of cost, time and training—for the prototyping and fabrication of MEMS parts that have larger dimensions, high aspect ratios, and complex shapes. In recent years, significant advancements in materials chemistry, laser technology, heat and fluid modeling, and control systems have enabled additive manufacturing to achieve higher resolutions at the micrometer and nanometer length scales to be a viable technology for MEMS fabrication. Compared to traditional MEMS processes that rely heavily on expensive equipment and time-consuming steps, direct-write additive manufacturing techniques allow for rapid design-to-prototype realization by limiting or circumventing the need for cleanrooms, photolithography and extensive training. With current direct-write additive manufacturing technologies, it is possible to fabricate unsophisticated micrometer scale structures at adequate resolutions and precisions using materials that range from polymers, metals, ceramics, to composites. In both academia and industry, direct-write additive manufacturing offers extraordinary promises to revolutionize research and development in microfabrication and MEMS technologies. Importantly, direct-write additive manufacturing could appreciably augment current MEMS fabrication technologies, enable faster design-to-product cycle, empower new paradigms in MEMS designs, and critically, encourage wider participation in MEMS research at institutions or for individuals with limited or no access to cleanroom facilities. This article aims to provide a limited review of the current landscape of direct-write additive manufacturing techniques that are potentially applicable for MEMS microfabrication.

Inkwells for on-demand deposition rate measurement in aerosol-jet based 3D printing

Aerosol-jet printing (AJP) is an important direct-write printing technology based on additive manufacturing methods. Numerous research groups have utilized AJP for the fabrication of electronic circuits and devices. However, there has not been any real-time or even any on-demand method for quantitatively measuring and/or setting the deposition rate of an AJ ink stream. In this paper, we present a method for measuring the deposition rate of an AJ ink stream by printing into an array of inkwells that were fabricated using photolithography and were characterized using x-ray tomography and optical profilometry. These inkwell arrays were then used to establish a set of deposition rates namely 0.0011, 0.0024, 0.0035, 0.0046 and 0.0059 mm3 s−1 that were subsequently compared with independently-measured deposition rates obtained by printing the ink stream into a weighing pan for a specified time and calculating the resulting deposition rate from the weight of the printed sample. From this comparison, it is observed that, for a human operator, the error in setting a specific deposition rate is less for inkwell fill times greater than 3 s and greater for fill times less than 3 s. This observation indicates that the average volume of an inkwell array should be at least three times the desired deposition rate (Vinkwell > 3R). It was also observed that when the diameter of the inkwell was only slightly larger than the ink stream diameter, the ink uniformly wets the sidewall of the inkwell and results in a well filled inkwell for which the point at which it is just fully filled is easily observable. Finally, the interactions of the ink with both ‘philic’ and ‘phobic’ inkwells were studied illustrating the ability to use inkwells of various materials for setting the desired deposition rates for a variety of AJ printable inks.

Ultralow flexural properties of copper microhelices fabricated via electrodeposition-based three-dimensional direct-writing technology.

Helical metallic micro/nanostructures as functional components have considerable potential for future miniaturized devices, based on their unique mechanical and electrical properties. Thus, understanding and controlling the mechanical properties of metallic helices is desirable for their practical application. Herein, we implemented a direct-writing technique based on the electrodeposition method to grow copper microhelices with well-defined and programmable three-dimensional (3D) features. The mechanical properties of the 3D helical structures were studied by the electrically induced quasistatic and dynamic electromechanical resonance technique. These methods mainly explored the static pull-in process and the dynamic electromechanical response, respectively. It was found that the center-symmetric and vertical double copper microhelix structure with 1.2 μm wire diameter has a flexural rigidity of 0.9 × 10-14 N m2 and the single vertical copper microhelix structure with 1.1 μm wire diameter has a flexural rigidity of 0.5989 × 10-14 N m2. By comparing with microwires and other reported micro/nanohelices, we found that the copper microhelices reported here had an ultralow stiffness (about 0.13 ± 0.01 N m-1). It is found that the experimental results agree well with the finite element calculations. The proposed method can be used to fabricate and measure the flexural properties of three-dimensional complex micro/nanowire structures, and may have a profound effect on the application of microhelices in various useful microdevices such as helix-based microelectromechanical switches, sensors and actuators based on their unique mechanical properties.

Rheology behaviors of stable electrohydrodynamic direct-write jet

Electrohydrodynamic direct-write (EDW) is a novel direct-write technology to fabricate micro/nano-structures from viscoelastic solution, which had displayed great application potential in organic electronic device. Due to the shorter spinneret to substrate distance, the rheology behaviors of EDW charged jet played an important role in defining the line width or diameter of the direct-written micro/nano-structures. High speed camera is utilized to observe the rheology process of EDW charged jet, and solidified jets are measured by SEM that offers a quantitative method to investigate the diameter evolution of jet. The diameter of charged jet and nanofiber injected from solid probe increase with the increasing of polymer solution concentration. Attribute to the larger diameter and higher solvent content, charged jet injected from hollow nozzle displayed greater fluid viscoelasticity, and then stretched into micro structure of flat film under the gravitation on the substrate. The diameter of charged jet and line width of thin film injected from nozzle decrease with the increasing of polymer concentration.

Mode-Selecting Micrograting Cavity Laser

We demonstrate a novel mode-selecting microcavity laser composed of gratings and a microdisk and fabricated by femtosecond-laser direct-writing technology. The microcavity laser shows good directivity and a single longitudinal mode, resulting from the mode coupling between the microdisk and gratings. The lasing wavelength can be regulated by adjusting the grating period. The properties of the laser were investigated and show good agreement with theoretical calculation and simulation. Based on the behavior and properties, this novel microcavity laser demonstrates good application prospects in integrated microoptics devices.

Carbon based resistive strain gauge sensor fabricated on titanium using micro-dispensing direct write technology

Carbon based resistive strain gauge sensor suitable for medical implant technology has been directly fabricated on a titanium test-plate using Micro-Dispensing Direct Write (MDDW) technology. A 3.5μm biocompatible dielectric layer of parylene C was initially coated on the titanium test-plate. Commercially available screen-print carbon conductive paste was deposited on the parylene C and cured at 80°C for 3h; this was to ensure the physical properties and chemical integrity of the parylene C layer was maintained, whilst meeting the electrical conductivity curing requirements for the carbon tracks. The novel integrated strain sensor was experimentally tested and found to have a gauge factor of 10 making it approximately 5 times more sensitive than a commercially available metal foil strain gauge glued to the same titanium plate.

Three-Dimensional Printing of Multifunctional Nanocomposites: Manufacturing Techniques and Applications.

The integration of nanotechnology into three-dimensional printing (3DP) offers huge potential and opportunities for the manufacturing of 3D engineered materials exhibiting optimized properties and multifunctionality. The literature relating to different 3DP techniques used to fabricate 3D structures at the macro- and microscale made of nanocomposite materials is reviewed here. The current state-of-the-art fabrication methods, their main characteristics (e.g., resolutions, advantages, limitations), the process parameters, and materials requirements are discussed. A comprehensive review is carried out on the use of metal- and carbon-based nanomaterials incorporated into polymers or hydrogels for the manufacturing of 3D structures, mostly at the microscale, using different 3D-printing techniques. Several methods, including but not limited to micro-stereolithography, extrusion-based direct-write technologies, inkjet-printing techniques, and popular powder-bed technology, are discussed. Various examples of 3D nanocomposite macro- and microstructures manufactured using different 3D-printing technologies for a wide range of domains such as microelectromechanical systems (MEMS), lab-on-a-chip, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems are reviewed. Parallel advances on materials and techniques are still required in order to employ the full potential of 3D printing of multifunctional nanocomposites.

Direct Write 기술을 이용한 3DCD의 제작

Direct Write 기술을 이용한 3DCD의 제작

All dispenser printed flexible 3D structured thermoelectric generators

This work presents a vertically fabricated 3D thermoelectric generator (TEG) by dispenser printing on flexible polyimide substrate. This direct-write technology only involves printing of electrodes, thermoelectric active materials and structure material, which needs no masks to transfer the patterns onto the substrate. The dimension for single thermoelectric element is 2 mm × 2 mm × 0.5 mm while the distance between adjacent cubes is 1.2 mm. The polymer structure layer was used to support the electrodes which are printed to connect the top ends of the thermoelectric material and ensure the flexibility as well. The advantages and the limitations of the dispenser printed 3D TEGs will also be evaluated in this paper. The proposed method is potential to be a low-cost and scalable fabrication solution for TEGs.

Feasibility of Fiber-Deposition Control by Secondary Electric Fields in Near-Field Electrospinning

Product miniaturization has become a trending technology in a broad range of industries and its development is being pushed by the requirements for complexity and resolution of micromanufactured products. However, there still exists a gap in the manufacturing spectrum for complex three-dimensional (3D) structure generation capabilities with micron and submicron resolution. This paper extends the near-field electrospinning (NFES) process and develops a direct-writing (DW) technology for microfiber deposition with micrometer resolution. The proposed method presented uses an auxiliary electrode to generate an electric field perpendicular to the fiber flight path. This tunable electric field grants the user real-time control of the fiber flight path, increasing the resolution of the deposited structure. The use of an auxiliary electrode ring for fiber manipulation is proposed to further improve control over the deposition process.

Hybrid fabrication process of additive manufacturing and direct writing for a 4×4 mm matrix flexible tactile sensor

Various machines require data from their external environments for safety and/or accuracy. In this respect, many sensors that mimic the human sensory system have been investigated. Among these, tactile sensors may be useful for obtaining data on the roughness of, and external forces acting upon, an object. Several tactile sensors have been developed; however, these are typically fabricated via a series of complex processes, and hence are unsuitable for volume manufacturing. In this paper, we report a fabrication process for a 4×4 mm matrix flexible sensor element using layered manufacturing and direct-write technology. A composite composed of photocurable resin and Multi-walled carbon nanotubes (MWCNTs) was used as the sensing material. The MWCNTs were mixed with the photocurable resin using ultrasonic dispersion, and the liquid mixture exhibited excellent piezoresistive properties following curing using ultraviolet light. The used photocurable resin is flexible and elastic after curing. Therefore, the composite material can be bent and deformed. To use this composite material with the flexible sensor, dispensing characteristics were examined using direct-write technology. For the acquisition of sensor data, a commercial pin-header was inserted and photocurable resin was filled up to the height of pin-header and cured. Then, the composite material was dispensed onto the pin-header as a sensing material. Using this process, a flexible sensor with piezoresistive properties was formed.

Spatially modulated laser pulses for printing electronics

The use of a digital micromirror device (DMD) in laser-induced forward transfer (LIFT) is reviewed. Combining this technique with high-viscosity donor ink (silver nanopaste) results in laser-printed features that are highly congruent in shape and size to the incident laser beam spatial profile. The DMD empowers LIFT to become a highly parallel, rapidly reconfigurable direct-write technology. By adapting half-toning techniques to the DMD bitmap image, the laser transfer threshold fluence for 10 μm features can be reduced using an edge-enhanced beam profile. The integration of LIFT with this beam-shaping technique allows the printing of complex large-area patterns with a single laser pulse.

Sessile drop deformations under an impinging jet

The problem of steady axisymmetric deformations of a liquid sessile drop on a flat solid surface under an impinging gas jet is of interest for understanding the fundamental behavior of free surface flows as well as for establishing the theoretical basis in process design for the Aerosol \({{\rm Jet}^{\circledR}}\) direct-write technology. It is studied here numerically using a Galerkin finite-element method, by computing solutions of Navier–Stokes equations. For effective material deposition in Aerosol \({{\rm Jet}^{\circledR}}\) printing, the desired value of Reynolds number for the laminar gas jet is found to be greater than ~500. The sessile drop can be severely deformed by an impinging gas jet when the capillary number is approaching a critical value beyond which no steady axisymmetric free surface deformation can exist. Solution branches in a parameter space show turning points at the critical values of capillary number, which typically indicate the onset of free surface shape instability. By tracking solution branches around turning points with an arc-length continuation algorithm, critical values of capillary number can be accurately determined. Near turning points, all the free surface profiles in various parameter settings take a common shape with a dimple at the center and bulge near the contact line. An empirical formula for the critical capillary number for sessile drops with \({45^{\circ}}\) contact angle is derived for typical ranges of jet Reynolds number and relative drop sizes especially pertinent to Aerosol \({{\rm Jet}^{\circledR}}\) printing.