UV Patterning Research Articles

A low-cost alternative method of generating fibronectin micropatterned lines for cellular applications

The cellular microenvironment contributes to the architecture, differentiation, polarity, mechanics and functions of the cell [1]. Spatial confinement of cells using micropatterning techniques allows to alter and regulate the cellular microenvironment for a better understanding of cellular mechanisms [2]. However, commercially available micropatterned consumables such as coverslips, dishes, plates etc. are expensive.These methods are complex and based on deep UV patterning [3,4]. In this study, we establish a low-cost method for effective micropatterning using Polydimethylsiloxane (PDMS) chips.•We demonstrate this method by generating fibronectin-coated micropatterned lines (width, 5 µm) on a glass bottom dish.•As a proof of concept, we culture macrophages on these lines. We additionally show that this method allows to determine the cellular polarity by measuring the position of the nucleus within a cell on a micropatterned line.

25‐2: Invited Paper: Ultra‐High‐Resolution NanoLED Panel for AR/VR by UV Patterning Technology

We report and discuss UV patterning technology of nanoLED with ultra‐high‐resolution. Additionally, we also report on the performances of the ultra‐high‐resolution nanoLED panel for ARJVR by UV patterning technology.

Triboelectric UV patterning for wearable one-terminal tactile sensor array to perceive dynamic contact motions

Triboelectric nanogenerators (TENGs) have attracted intensive attention for the self-powered tactile signalling because strong potential signals are generated even by weak mechanical stimuli. The TENG-based sensors typically request one or two interconnecting wires in each pixel, hence a large number of interconnections are necessary to acquire multiple position information. Here, we introduce innovative triboelectric UV patterning on a single stretchable elastomer dielectric film and fabricate a position-encoded tactile sensor requiring only one interconnection line. We investigate controllable change of triboelectric potentials simply adjustable by UV irradiation time on saturated thermoplastic block copolymers. The one-terminal triboelectrically-patterned tactile sensor (TPTS) perceives the position and time of dynamic contact motions such as sliding, ball rolling, sequential or simultaneous touches, and grasping. We believe that this study will pave the way for the novel design of self-powered tactile sensors for various applications such as artificial skin.

Tunable Structural Color Images by UV‐Patterned Conducting Polymer Nanofilms on Metal Surfaces (Adv. Mater. 33/2021)

Structural Color Images In article number 2102451, Magnus P. Jonsson and co-workers demonstrate a new approach to produce dynamic structural colors with UV-patterned conducting polymers. The UV patterning controls the film thickness and polymer permittivity, and enables production of multicolor images with a single exposure step. Combined with the electrochemical tunability of the conducting polymer, these devices hold promise for next-generation multifunctional displays.

Triboelectric Uv Patterning for Wearable One-Terminal Tactile Sensor Array to Perceive Dynamic Contact Motions

Triboelectric Uv Patterning for Wearable One-Terminal Tactile Sensor Array to Perceive Dynamic Contact Motions

The study of correlation between electrical conductivity of solution-processed ZnO film and UV irradiation

This study investigated the correlation between the electrical conductivity of solution-processed ZnO film and UV irradiation. As-deposited ZnO film without UV irradiation was found to have a high resistivity, while the resistivity of UV irradiated ZnO film drastically decreased, owing to photo-induced doping under UV irradiation. The effect of UV intensity on the decomposition rate of organic substance indicated proportional relation. In addition, a transparent electric circuit was fabricated by UV patterning.

Process and characterization of photo-definable organic–inorganic dielectric for wafer level packaging

The introduction of an organic–inorganic dielectric material into the redistribution layers in fan-out wafer level packaging technology has been investigated to improve mechanical stress, thermal stability, and electrical breakdown compared to organic dielectric materials. A photo-definable organic–inorganic dielectric material called polysilsesquioxane (PSSQ) has been studied in this work. The photo-definable PSSQ dielectric allows a simultaneous UV patterning and curing process. A PSSQ sample was prepared by spin-coating on a 6-in. Si wafer, pre-baking at 100 °C for 5 min, UV exposure, and then PGMA developing. The cured PSSQ films have a dielectric constant from 2.0 to 2.38 and dielectric loss from 0.0001 to 0.005. In addition, the 2 μm line patterns were obtained after 10 min of UV exposure. It has been demonstrated that PSSQ dielectric materials can provide excellent process capability of simultaneous UV patterning and curing process.

Optimization of Recovery and Relaxation of Acrylic Pressure-Sensitive Adhesives by Using UV Patterning for Flexible Displays

For flexible displays, recovery and relaxation of acrylic pressure-sensitive adhesives (PSA) must be enhanced; however, only a few studies have focused on their optimization. High cross-linking density of the PSA leads to improved recovery but deteriorates the stress relaxation; thus, it is difficult to perform optimization by simply controlling the cross-linking density. Herein, it was determined that a UV-patterned PSA with both high and low cross-linking densities in a single layer enables the optimization of both recovery and relaxation. By introducing the UV-patterned PSA, the elasticity and recovery largely deteriorated but the stress relaxation was significantly improved, compared to that of the nonpatterned PSA, and this effect was enhanced with increases in the applied strain. Thereby, the recovery and relaxation were well-optimized with both values above 71% only at 300% strain. The recovery and relaxation of PSA had, respectively, a positive and negative correlation with the storage modulus.

Greyscale and Paper Electrochromic Polymer Displays by UV Patterning.

Electrochromic devices have important implications as smart windows for energy efficient buildings, internet of things devices, and in low-cost advertising applications. While inorganics have so far dominated the market, organic conductive polymers possess certain advantages such as high throughput and low temperature processing, faster switching, and superior optical memory. Here, we present organic electrochromic devices that can switch between two high-resolution images, based on UV-patterning and vapor phase polymerization of poly(3,4-ethylenedioxythiophene) films. We demonstrate that this technique can provide switchable greyscale images through the spatial control of a UV-light dose. The color space was able to be further altered via optimization of the oxidant concentration. Finally, we utilized a UV-patterning technique to produce functional paper with electrochromic patterns deposited on porous paper, allowing for environmentally friendly electrochromic displays.

Soft Lithography, Molding, and Micromachining Techniques for Polymer Micro Devices.

This chapter enumerates the methods, protocol, and safety procedures of various fabrication techniques for polymer-based microfluidic devices. The polymer materials can be a solid or a liquid, and the fabrication protocol needs to be executed accordingly. Various techniques demonstrating the fabrication of microfluidic devices using solid and liquid polymers are described. Procedure for each fabrication process is delineated with detailed images. Further, dos and don'ts for all the fabrication techniques are explained in the notes of each section. This chapter will benefit those interested in the microfluidic device fabrication using polymers and guide them to avoid mistakes so as to obtain an elegant device.The techniques are listed as follows: 1. Replica molding 2. Microcontact printing 3. Micro-transfer molding 4. Solvent-assisted molding 5. Hot embossing 6. Injection molding 7. CNC micromachining 8. Laser photo ablation 9. X-ray lithography 10. UV patterning 11. Plasma etching 12. Ion beam etching 13. Capillary molding 14. Micro-stereolithography.

Optimization of laser writer-based UV lithography with high magnification optics to pattern X-ray lithography mask templates

Deep X-ray lithography is a preferred fabrication approach for those micro devices that depend on smooth and vertical sidewalls of comparatively deep structures rather than extreme lateral resolution. The structure quality obtained depends on, and is limited by, the quality of the X-ray mask applied. A critical component of the mask is its absorber patterns. They get fabricated by electroplating into voids of a polymer template. These templates must usually be at least 3 μm deep and exhibit smooth and vertical sidewalls with a lateral resolution of micrometers and possibly below. Primary patterning of the templates is very demanding. Best results are obtained when dedicated electron beam writers with acceleration voltages of 100 kV and above are applied. This, however, limits access to patterning infrastructure and substantially drives delivery timeline and cost, making mask absorber template patterning a bottleneck of the entire process sequence. We propose, evaluate and optimize an alternative absorber patterning approach based on direct laser writing. An ultraviolet laser with 355 nm wavelength and 250 mW beam power by Heidelberg Instruments is applied to expose 2.9 μm thick, chemically amplified, high contrast, negative tone resist mrx-5. Exposure parameters analyzed include the dose and focal settings. Experiments are carried out on bare silicon wafers as well as on chrome-gold and on titanium oxide plating bases. For all cases, results with and without an additional antireflective coating of 200 nm AZ BAR-Li are studied. Aspects of the resist template structure quality analyzed include the sidewall verticality and its smoothness and defects, resist adhesion to the substrate, minimum feature size and structure accuracy, as well as irregularities due to stitching of partial layouts. In an optimized process, a dose of 14 mW on oxidized titanium and BAR-Li was used. We were able to demonstrate 1.5 μm minimum feature size of isolated structures and structural details of about 1 μm. The sidewalls are vertical and exhibit a roughness of dozens of nanometers. When an antireflective coating is used, chamfers are observed at the resist bottom. The structure accuracy occasionally deviates from the original layout by 200–300 nm, particularly at stitching singularities or towards the end of resist walls. The described absorber template patterning process delivers a resolution that much extends beyond previous UV patterning approaches. The structure accuracy, however, is inferior to electron beam written samples. Given the cost and timeline benefit, results of the study will allow users to identify which primary patterning approach is best suited for their micro devices.

A Programmable DNA Double-Write Material: Synergy of Photolithography and Self-Assembly Nanofabrication.

We demonstrate a DNA double-write process that uses UV to pattern a uniquely designed DNA write material, which produces two distinct binding identities for hybridizing two different complementary DNA sequences. The process requires no modification to the DNA by chemical reagents and allows programmed DNA self-assembly and further UV patterning in the UV exposed and nonexposed areas. Multilayered DNA patterning with hybridization of fluorescently labeled complementary DNA sequences, biotin probe/fluorescent streptavidin complexes, and DNA patterns with 500 nm line widths were all demonstrated.

Etch-free addressable organic sensor arrays

Using a direct UV fabrication technique, an organic transparent 8×8 capacitive touch screen panel has been designed, fabricated and characterized. The active electrode material is poly(3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS). The UV process provided spatial control over the PEDOT:PSS film conductivity, which was subsequently used to fabricate the touch screen panel. This process does not require external photoresists or secondary development and etch steps. The UV patterning of PEDOT:PSS provided a 3-order-of-magnitude reduction in material conductivity between exposed and unexposed regions. Spatial location of touch events can be accurately identified by monitoring relative changes in capacitance at each of the individual elements of the array. A typical touch event causes a measured capacitance reduction of ∼100fF at the touched intersection. The tested devices exhibit high optical transmission exceeding 80% across the visible spectrum. This technology allowed the device to be realized in a single processing step that is amenable to large scale, high-throughput organic fabrication techniques such as roll-to-roll processing.

Transparent and fluorescent thin films of polysilane–SiQD nanocomposite: cellulose acetate

Fluorescent and highly transparent free standing thin films have been prepared using polysilane–silicon quantum dots nanocomposite (PSiQD) dispersed within cellulose triacetate (CA). Polysilane acts like a carrier that transports the silicon quantum dots (SiQDs) within the CA matrix. Extremely low, subcatalytic amounts of PSiQD are enough to transfer to CA the optical properties of both polysilane and SiQDs. Thin films obtained by solvent casting are mechanically resistant, highly flexible and show the characteristic high intensity fluorescent emission due to SiQDs. Also, the nanocomposite is UV photosensitive and could be easily converted to a hydrophilic material, compatible with the common paper. The PSiQD carrier is obtained in situ by microwave assisted coupling of chlorosilanes in heterogeneous reaction conditions. ATR-FTIR analysis was used to investigate the chemical structure within the bulk material. The presence of SiQDs and their content within the CA nanocomposite were proved by XPS. These results were further sustained by TEM and SAXS analysis. The wetting properties of the composite were probed before and after UV exposure by contact angle measurements. Thin films of such a nanocomposite material are designed for special opto-electronic applications that require processing by UV patterning and control of surface wetting properties.

Successes and frontiers in extreme UV patterning

Successes and frontiers in extreme UV patterning

Genetic architecture, biochemical underpinnings and ecological impact of floral UV patterning.

Floral attraction traits can significantly affect pollinator visitation patterns, but adaptive evolution of these traits may be constrained by correlations with other traits. In some cases, molecular pathways contributing to floral attraction are well characterized, offering the opportunity to explore loci potentially underlying variation among individuals. Here, we quantify the range of variation in floral UV patterning (i.e. UV 'bulls-eye nectar guides) among crop and wild accessions of Brassica rapa. We then use experimental crosses to examine the genetic architecture, candidate loci and biochemical underpinnings of this patterning as well as phenotypic manipulations to test the ecological impact. We find qualitative variation in UV patterning between wild (commonly lacking UV patterns) and crop (commonly exhibiting UV patterns) accessions. Similar to the majority of crops, recombinant inbred lines (RILs) derived from an oilseed crop × WI fast-plant® cross exhibit UV patterns, the size of which varies extensively among genotypes. In RILs, we further observe strong statistical-genetic and QTL correlations within petal morphological traits and within measurements of petal UV patterning; however, correlations between morphology and UV patterning are weak or nonsignificant, suggesting that UV patterning is regulated and may evolve independently of overall petal size. HPLC analyses reveal a high concentration of sinapoyl glucose in UV-absorbing petal regions, which, in concert with physical locations of UV-trait QTLs, suggest a regulatory and structural gene as candidates underlying observed quantitative variation. Finally, insects prefer flowers with UV bulls-eye patterns over those that lack patterns, validating the importance of UV patterning in pollen-limited populations of B. rapa.

Photopatternable Laminate BCB Dielectric

Divinylsiloxane-bis-benzocyclobutene (DVS-bis-BCB, or BCB) is a well-known dielectric material that has been used in high volume manufacturing for many years (Dow's CYCLOTENE™ 3000/4000-series Advanced Electronic Resins). Typically, the application of these products has been by spincoating or spray coating of the dielectric material from a solvent-based formulation. However, for certain applications - for example, those involving large area, square substrates such as glass panels - it is desirable to be able to apply the BCB-based dielectric material using a dry film coating process, such as vacuum or hot roll lamination. In this paper, we describe the concept of creating a laminate film utilizing DVS-bis-BCB as the primary dielectric material component. In creating the laminate dielectric material, it is important to maintain the unique combination of thermal and electrical properties of DVS-bis-BCB, including high thermal stability, excellent copper barrier properties, low moisture uptake, low dielectric constant, and low dielectric loss. However, DVS-bis-BCB alone is too rigid to produce a high quality laminate film, therefore, it is necessary to modify the formulation to improve flexibility and lamination quality. As the flexibility of the film is increased, higher fracture toughness (K1C) and higher elongation values should result. Novel formulation adjustments to the base DVS-bis-BCB polymer system have resulted in an experimental laminate dielectric product that will be the focus of this discussion. Depending on the application, laminate films can vary in thickness from 2μm to 50μm or even thicker. A typical laminate film construct includes the BCB-based dielectric film with a base sheet of an optically-clear polyester (PET) film and a polyethylene (PE) cover sheet. The DVS-bis-BCB-based laminate can be tuned with appropriate additives to either pattern with UV exposure from a tool such as a Süss MicroTec Mask Aligner (50mJ/cm2 – 100mJ/cm2 exposure energy) or laser pattern with a tool such as a Süss MicroTec 248nm Excimer Laser. Aspect ratios of 1:1.5 have been achieved with a photopatternable DVS-bis-BCB film and aspect ratios of >1:1 are possible with a laser-patterned film. Beside the photopackage added to the film to enable UV patterning, toughening additives have also been incorporated to enhance the fracture toughness (K1C) and elongation properties. K1C for the laminate has been improved to 0.55Mpa·m1/2 vs. 0.35Mpa·m1/2 for DVS-bis-BCB. Elongation has been improved to 13% for the laminate vs. 8% for DVS-bis-BCB. Electrical properties are similar to DVS-bis-BCB. An additional attribute of the laminate dielectric is the ability to tent over and protect vias. Vias >100μm diameter have successfully been tented with a 10μm thick film. A DVS-bis-BCB-based laminate has been demonstrated with continued optimization and evaluation to follow.

Reversible metallisation of soft UV patterned substrates

Patterned surface created through soft UV (365 nm) patterning of ortho-nitrobenzyl functionalized thiol-on-gold self-assembled monolayers (SAMs) is suitable for electro-deposition with high selectivity and fully reversibility of deposition/stripping process.

UV경화성 폴리머를 이용한 미소유체 통합접속 벤치 개발 및 전기/유체적 특성평가

본 논문은 고차가지구조 폴리머인 AEO3000 를 이용한 UV 광경화 성형 공정을 제안하고자 한다. 이는 기존의 바이오칩 제작에 사용되는 PDMS 보다 경도가 높아 금속 전극 형성이 용이하고 제작 공정이 빠르다는 장점을 갖는다. AEO3000 을 이용하여 본 연구에서는 4개의 소자를 전기적·유체적으로 연결할 수 있는 전기유체 통합벤치를 제작하고 미소유체 혼합소자와 세포분리소자를 연결, 본 소재와 공정이 바이오칩에 적용될 수 있음을 검증하였다. 전기 유체적 특성 분석 결과 전기적 접촉 저항은 0.75±0.44F 으로 충분히 작은 값을 보였으며, 유체 접속의 압력 저하는 8.3kPa로 기존의 튜브 연결 방법 대비 39.3% 개선된 값을 보였다. 통합벤치에 접속된 소자에 활성 및 비활성 효모를 주입하여 순차적인 혼합 및 재분리를 성공적으로 구현함으로써 본 소자에 적용된 AEO3000 및 UV 광경화 공정이 생체시료의 처리에 적용될 수 있음을 실험적으로 검증하였다. 이는 바이오 의료 분야에 적용 가능한 생체 친화적 소재의 고속 생산에 응용될 수 있다.

Direct-write maskless lithography of LBL nanocomposite films and its prospects for MEMS technologies.

Application of nanocomposites in MEMS, flexible electronics, and biomedical devices is likely to demonstrate new performance standards and resolve a number of difficult technical problems enabled by the unique combinations of electrical, optical, and mechanical properties. This study explores the possibility of making microscale nanocomposite patterns using the fusion of two highly versatile techniques: direct-write maskless UV patterning and layer-by-layer assembly (LBL). Together they can be applied to the production of a wide variety of nanostructured coatings with complex patterns. Single-walled carbon nanotube (SWNT) and gold nanoparticle LBL nanocomposites assembled with chitosan (CH) were made into prototypical patterns such as concentric helices and bus-line-and-stimulation-pads (BLASPs) used in flexible antennas and neuroprosthetic devices. The spatial resolution of the technique was established with the standard line grids to be at least 1 μm. Gold nanoparticle films revealed better accuracy and higher resolution in direct-write patterning than SWNT composites, possibly due to the granular rather than fibrous nature of the composites. The conductivity of the patterned composites was 6.45 × 10(-5)Ω m and 3.80 × 10(-6)Ω m at 20 °C for nanotube and nanoparticle composites, respectively; in both cases it exceeds electrical parameters of similar composites. Fundamental and technological prospects of nanocomposite MEMS devices in different areas including implantable biomedical, sensing, and optical devices are discussed.