High-resolution Printing Techniques Research Articles

Tilting behaviors of metal microjet in laser-induced forward transfer

Abstract Laser-induced forward transfer (LIFT) is proposed as a highly efficient and high-resolution printing technique. Tilting of the microjet in the LIFT process affects the deposition deviation, lowing the printing resolution. We investigate the tilting behaviors of the metal microjet in the nanosecond LIFT process based on high-speed observation. Experiments were conducted on the copper film under different laser fluences. Observations based on the pump-probe method were performed to capture the ejection behavior of microjets. We find that the tilting direction is isotropic and the tilting angle follows Gaussian distribution. The tilting behavior originates from the disturbance of residual stress within the film during jet generation because the statistical results of the tilting angle hardly vary with the propagation time. In addition, the tilting angle is found to decrease linearly with the laser fluence due to the ejection velocity increasing at a higher rate than the lateral velocity. The lateral offset of the tilting microjet at different flight distances matches well with the position deviations, verifying the tilting behavior of the microjet. This study provides essential comprehension of the tilting behavior of metal microjet in the LIFT process.

Printed n- and p-Channel Transistors using Silicon Nanoribbons Enduring Electrical, Thermal, and Mechanical Stress.

Printing technologies are changing the face of electronics with features such as resource-efficiency, low-cost, and novel form factors. While significant advances have been made in terms of organic electronics, the high-performance and stable transistors by printing, and their large-scale integration leading to fast integrated circuits remains a major challenge. This is because of the difficulties to print high-mobility semiconducting materials and the lack of high-resolution printing techniques. Herein, we present silicon based printed n- and p-channel transistors to demonstrate the possibility of developing high-performance complementary metal-oxide-semiconductor (CMOS) computing architecture. The direct roll transfer printing is used here for deterministic assembly of high-mobility single crystal silicon nanoribbons arrays on a flexible polyimide substrate. This is followed by high-resolution electrohydrodynamic printing to define source/drain/gate electrodes and to encapsulate, thus leading to printed devices. The printed transistors show effective peak mobilities of 15 cm2/(V s) (n-channel) and 5 cm2/(V s) (p-channel) at low 1 V drain bias. Furthermore, the effect of electrical, mechanical, and thermal stress on the performance and stability of the encapsulated transistors is investigated. The transistors showed stable transfer characteristics even after: (i) continuous 4000 transfer cycles, (ii) excruciating 10000 bending cycles at different bending radii (40, 25, and 15 mm), and (iii) between 15 and 60 °C temperatures.

Comparison of jets from Newtonian and non-Newtonian fluids induced by blister-actuated laser-induced forward transfer (BA-LIFT)

Blister-actuated laser-induced forward transfer (BA-LIFT) is a high-resolution printing technique, where small droplets are ejected from a thin liquid layer onto a receiver substrate. Experiments with a high-speed camera imaging setup demonstrate novel regimes during the jet formation for the transfer of viscoelastic shear-thinning polymer solutions compared to Newtonian fluids. The ratio of the ink film thickness $$H_{\text {f}}$$ to the blister height $$H_{\text {b}}$$ is used as a dimensionless number $$H_{\text {f}}/H_{\text {b}}$$ to classify different jet behaviors. We show that different $$H_{\text {f}}/H_{\text {b}}$$ thresholds can be defined depending on the elasticity of the ink layer for the induced jets to result in breakup.

Nanocomposite polymer carbon-black coating for triggering pyro-electrohydrodynamic inkjet printing

The pyro-electrohydrodynamic (EHD) manipulation of liquids has been discovered and demonstrated recently as a high resolution printing technique avoiding the use of nozzles and external electrodes. The activation of the pyro-electric effect is usually achieved on ferroelectric crystals by an external heating source or by an infrared laser. Here, we show an original modality for triggering the pyro-EHD process through a light-absorbing polymer nanocomposite thin layer deposited on the ferroelectric substrate, thus overcoming some limitations of the previous configuration. Significant simplification and compactness of the set-up is achieved thanks to the nanocomposite coating, since a commercial low-cost white-light halogen lamp can be adopted to trigger the pyro-jetting process from a liquid reservoir. Remarkably, high resolution is achieved in dispensing very high viscous liquids. Practical demonstrations in polymer optical microlenses direct printing using polydimethylsiloxane and poly(methyl methacrylate) are finally reported to validate the approach in handling high-viscous polymers for practical applications.

Fabrication of Si-nozzles for parallel mechano-electrospinning direct writing

Nozzles with micro-scale orifices drive high-resolution printing techniques for generating micro- to nano-scale droplets/lines. This paper presents the fabrication and application of Si-nozzles in mechano-electrospinning (MES). The fabrication process mainly consists of photolithography, Au deposition, inductively coupled plasma, and polydimethylsiloxane encapsulation. The 6 wt% polyethylene oxide solution is adopted to study the electrospinning behaviour and the relations between fibre diameter and process parameters in MES. A fibre grid with 250 µm spacing is able to be direct written, and the diameters are less than 3 µm. To improve the printing efficiency, positioning accuracy and flexibility, a rotatable multi-nozzle is adopted. The distance between parallel lines reduces sharply from 4.927 to 0.308 mm with the rotating angle increasing from 0° to 87°, and the fibre grids with tunable distance are achieved. This method paves the way for fabrication of addressable Si-nozzle array in parallel MES direct writing.

ディスプレイ―ＩＤＷ’０７を中心に―全印刷法による電気泳動ディスプレイ用１０．５ｉｎｃｈ‐ＶＧＡフレキシブル有機ＴＦＴ背面板

We developed an all-printed flexible organic TFT with a channel length below 10μm and a mobility of over 0.01 cm2/Vs using an offset-based high-resolution printing technique and inkjet printing of small-molecule organic semiconductors. These technologies have been applied to a demonstration of a 10.5-inch VGA flexible active-matrix electrophoretic display driven by an all-printed organic TFT backplane.

A Micromachined Printhead for the Direct Evaporative Patterning of Organic Materials

We investigate the use of microsystems (MEMS) in the direct patterning of materials needed for organic optoelectronic devices on large area low-cost substrates.We present a new high-resolution printing technique for depositing molecular organic semiconductor materials on substrates. By depositing the materials directly from the gas phase, without liquid phase coming in contact with the substrate, we aim at avoiding the limitations encountered when inkjet printing such materials.One of the main advantages of this technique is that it does not require a vacuum, which is very significant for achieving lowcost fabrication.Our micromachined printhead was used, in conjunction with inkjet technology for the delivery of liquid phase material, to print patterns of organic material.

Printed thin-film transistors and complementary logic gates that use polymer-coated single-walled carbon nanotube networks

This paper reports on the electrical properties of thin-film transistors (TFTs) that use polymer-coated networks of single-walled carbon nanotubes (SWNTs) as the semiconductor with source and drain electrodes formed by high-resolution printing techniques. P-channel, n-channel, and ambipolar TFTs are demonstrated with bare SWNT networks, networks coated with polyethylene imine and with polyethylene oxide, respectively. Studies of the scaling of properties with channel length and tube density reveal important information about the operation of these devices. Complementary inverters made with n- and p-channel devices show gain larger than one and illustrate the potential use of these types of TFTs for complex logic circuits.

Printing Meets Lithography: Soft Approaches to High-Resolution Patterning

We are developing a high-resolution printing technique based on transferring a pattern from an elastomeric stamp to a solid substrate by conformal contact. This is an attempt to enhance the accuracy of classical printing to a precision comparable with optical lithography, creating a low-cost, large-area, high-resolution patterning process. First, we introduce the components of this technique, called soft lithography, and review its evolution. Topics described in detail are the stamp material, stamp architecture, pattern design rules, and printing tools. The accuracy of the prints made by thin patterned elastomeric layers supported on a stiff and flexible backplane is then assessed, and defects are characterized using a new electrical metrology approach. This is followed by a discussion of various printing processes used in our laboratory: (1) thiol printing for high-resolution patterns of noble metals that may also be used as sacrificial masks; (2) confined contact processing with liquids in cavities or channels to chemically convert a substrate or deposit layers of materials or biomolecules; (3) printing of catalysts to mediate patterned deposition of metals; and (4) structured, light-guiding stamps for transferring high-resolution patterns into photoresists. Finally, we compare classical and high-resolution printing approaches, and describe their potential for emerging micro- and nanoscale patterning technologies.

Printing meets lithography: Soft approaches to high-resolution patterning

We are developing a high-resolution printing technique based on transferring a pattern from an elastomeric stamp to a solid substrate by conformal contact. This is an attempt to enhance the accuracy of classical printing to a precision comparable with optical lithography, creating a low-cost, large-area, high-resolution patterning process. First, we introduce the components of this technique, called soft lithography, and review its evolution. Topics described in detail are the stamp material, stamp architecture, pattern design rules, and printing tools. The accuracy of the prints made by thin patterned elastomeric layers supported on a stiff and flexible backplane is then assessed, and defects are characterized using a new electrical metrology approach. This is followed by a discussion of various printing processes used in our laboratory: 1) thiol printing for high-resolution patterns of noble metals that may also be used as sacrificial masks; 2) confined contact processing with liquids in cavities or channels to chemically convert a substrate or deposit layers of materials or biomolecules; 3) printing of catalysts to mediate patterned deposition of metals; and 4) structured, light-guiding stamps for transferring high-resolution patterns into photoresists. Finally, we compare classical and high-resolution printing approaches, and describe their potential for emerging micro-and nano-scale patterning technologies.