Electrohydrodynamic direct-writing of conductor–insulator–conductor multi-layer interconnection

A multi-layer interconnection structure is a basic component of electronic devices, and printing of the multi-layer interconnection structure is the key process in printed electronics. In this work, electrohydrodynamic direct-writing （EDW） is utilized to print the conductor-insulator--conductor multi-layer ~nterconne^ction structure. Silver ink is chosen to print the conductor pattern, and a polyvinylpyrrolidone （PVP） solution is util^zed to f^bricate the insulator layer between the bottom and top conductor patterns. The influences of EDW process parameters on the line width of the printed conductor and insulator patterns are studied systematically. The obtained ~es^l~s show that the line width of the printed structure increases with the increase of the flow rate, but decreases with the increase of applied voltage and PVP content in the solution. The average resistivity values of the bottom and top silver conductor tracks are determined to be 1.34 × 10-7 Ω.m and 1.39×10-7 Ω.m, respectively. The printed PVP layer between the two conductor tracks is well insulated, which can meet the insulation requirement of the electronic devices. This study offers an alternative, fast, and cost-effective method of fabricating conductor-insulator-conductor multi-layer interconnections in the electronic industry.

Characterization on Modification and Biocompatibility of PCL Scaffold Prepared with Near-field Direct-writing Melt Electrospinning

In this study,orthogonal experiments were designed to explore the optimal process parameters for preparing polycaprolactone(PCL)scaffolds by the near-field direct-writing melt electrospinning(NFDWMES)technology.Based on the optimal process parameters,the PCL scaffolds with different thicknesses,gaps and structures were manufactured and the corresponding hydrophilicities were characterized.The PCL scaffolds were modified by chitosan(CS)and hyaluronic acid(HA)to improve biocompatibility and hydrophilicity.Both Fourier transform infrared spectroscopy(FTIR)analysis and antibacterial experimental results show that the chitosan and hyaluronic acid adhere to the surface of PCL scaffolds,suggesting that the modification plays a positive role in biocompatibility and antibacterial effect.The PCL scaffolds were then employed as a carrier to culture cells.The morphology and distribution of the cells observed by a fluorescence microscope demonstrate that the modified PCL scaffolds have good biocompatibility,and the porous structure of the scaffolds is conducive to adhesion and deep growth of cells.

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 compu- ter-generated solid models without elaborate intermediate fabrication steps. At the macroscale, direct-write techni- ques 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-dimen- sional models into layers of two-dimensional planes or slices, which are then reconstructed sequentially into three- dimensional solid objects in key differences between the a layer-by-layer format. The various additive manufactur- ing 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 equip- ment 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 manufacturingtechnologies, 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 extra- ordinary promises to revolutionize research and develop- ment 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.

Luminescent line art by direct-write patterning

We present a direct-write patterning method for the realization of electroluminescent(EL)line art using a surface-emissive light-emitting electrochemical cell with its electrolyte and EL material separated into a bilayer structure.The line-art emission is achieved through subtractive patterning of the electrolyte layer with a stylus,and the single-step patterning can be either manual for personalization and uniqueness or automated for high throughput and repeatability.We demonstrate that the light emission is effectuated by cation-assisted electron injection in the patterned regions and that the resulting emissive lines can be as narrow as a few micrometers.The versatility of the method is demonstrated through the attainment of a wide range of light-emission patterns and colors using a variety of different materials.Wepropose that this low-voltage-driven and easy-to-modify luminescent line-art technology could be of interest for emerging applications,such as active packaging and personalized gadgets.

Photonic lattice-like waveguides in glass directly written by femtosecond laser for on-chip mode conversion

We report on a conceptually new type of waveguide in glass by femtosecond laser direct writing,namely,photonic latticelike waveguide(PLLW).The PLLWfs core consists of well-distributed and densified tracks with a sub-micron size of 0.62μm in width.Specifically,a PLLW inscribed as hexagonal-shape input with a ring-shape output side was implemented to converse Gaussian mode to doughnut-like mode,and high conversion efficiency was obtained with a low insertion loss of 1.65 dB at 976 nm.This work provides a new freedom for design and fabrication of the refractive index profile of waveguides with sub-micron resolution and broadens the functionalities and application scenarios of femtosecond laser direct-writing waveguides in future 3D integrated photonic systems.

Flexible electronics manufacturing technology and equipment

Flexible electronics such as mechanically compliant displays,sensors and solar cells,have important applications in the fields of energy,national defence and biomedicine,etc.Various types of flexible electronics have been proposed or developed by the improvements in structural designs,material properties and device integrations.However,the manufacturing of flexible electronics receives little attention,which limits its mass production and industrialization.The increasing demands on the size,functionality,resolution ratio and reliability of flexible electronics bring several significant challenges in their manufacturing processes.This work aims to report the state-of-art technologies and applications of flexible electronics manufacturing.Three key technologies including electrohydrodynamic direct-writing,flip chip and automatic optical inspection are highlighted.The mechanism and developments of these technologies are discussed in detail.Based on these technologies,the present work develops three kinds of manufacturing equipment,i.e.,inkjet printing manufacturing equipment,robotized additive manufacturing equipment,and roll-to-roll manufacturing equipment.The advanced manufacturing processes,equipment and systems for flexible electronics pave the way for applications of new displays,smart sensing skins and epidermal electronics,etc.By reviewing the developments of flexible electronics manufacturing technology and equipment,it can be found that the existing advances greatly promote the applications and commercialization of flexible electronics.Since flexible electronics manufacturing contains many multi-disciplinary problems,the current investigations are confronted with great challenges.Therefore,further developments of the reviewed manufacturing technology and equipment are necessary to break the current limitations of manufacturing resolution,efficiency and reliability.