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Printed electronics such as solar cells, RFIDs, and display panels can be made using printed electronic technology by printing viscous liquids having various properties on films or insulating substrates. Among printed electronic production processes, the roll-to-roll process transfers functional ink to an insulation substrate by filling its engravings through repeated contact and rotation of two rolls. Extensive research has been conducted to commercialize this process because it offers several advantages such as low equipment investment and production cost, and high-speed mass production. However, the roll-to-roll process requires further development for commercialization because print quality precision and fine pattern formation are difficult to achieve, and print quality may be affected by processing precision errors and non-uniform printing pressure. Contact printing pressure is the pressure acting on the nip that makes contact with the two rolls, and is a factor that influences roll processing precision. That is, contact printing pressure uniformity must be maintained to enhance print quality. However, previous research on contact printing pressure failed to directly estimate the contact printing pressure due to structural problems, and only indirectly measured it by attaching a load cell at both ends of the impression roll. This study proposes a method of contact printing pressure estimation and control to enhance print quality. The processing precision of a roll can be measured by measuring the rotationally repeatable run-out after dividing the width of the impression roll and plate roll into 25 points. The relationship between the impression roll and the plate roll, with consideration of the contact printing pressure, rotationally repeatable run-out, and force measured by the load cell, is modeled in a manner similar to the relationship between a car body, suspension, and ground in a half-car model, and expressed using state-space equations. This model is then applied to an individual drive type cross-coupled control system for experiments on control of the contact printing pressure; pressure measuring films are used to check for actual improvement in uniformity of contact printing pressure.

When an elastomeric photomask is used for near-field contact printing, the high deformability of the elastomer mask plate enables gap-free full contact with the substrate, minimizing the effect of diffraction. This image-transfer technique provides sub-50 nm resolution and depth-of-focus-free lithographic capability with cost-efficient equipment. However, the method’s application is limited due to the lack of a wellestablished protocol for fabricating a nanoscale mask pattern on an elastomeric substrate, which remains a major technical challenge in the field of near-field contact printing. In this study, we present a reliable protocol for fabricating a metal-embedded polydimethylsiloxane (PDMS) photomask. Our fabrication protocol uses conventional nanofabrication processes to fabricate nanosized chromium mask patterns and then transfers the chromium patterns to an elastomeric mask plate using a sacrificial Ni layer. Our protocol provides a high flexibility mask pattern design, and highly stable metal patterns during transferring process. By careful optimizing the experimental parameters, we determined a perfect pattern transfer ratio, which avoided any mechanical failure of the metal pattern, such as debonding or wrinkling. We then fabricated a PDMS photomask and confirmed its nanoscale patterning resolution, with the smallest feature 51 nm in width under a 400-nm light source. We anticipate that our fabrication protocol will enable the application of cost-efficient and high-resolution near-field photolithography. (Received September 23, 2020; Accepted December 13, 2020)

The Printed Electronics (PE) is expected to revolutionise the way electronics will be manufactured in the future. Building on the achievements of the traditional printing industry, and the recent advances in flexible electronics and digital technologies, PE may even substitute the conventional silicon-based electronics if the performance of printed devices and circuits can be at par with silicon-based devices. In this regard, the inorganic semiconducting materials-based approaches have opened new avenues as printed nano (e.g. nanowires (NWs), nanoribbons (NRs) etc.), micro (e.g. microwires (MWs)) and chip (e.g. ultra-thin chips (UTCs)) scale structures from these materials have been shown to have performances at par with silicon-based electronics. This paper reviews the developments related to inorganic semiconducting materials based high-performance large area PE, particularly using the two routes i.e. Contact Printing (CP) and Transfer Printing (TP). The detailed survey of these technologies for large area PE onto various unconventional substrates (e.g. plastic, paper etc.) is presented along with some examples of electronic devices and circuit developed with printed NWs, NRs and UTCs. Finally, we discuss the opportunities offered by PE, and the technical challenges and viable solutions for the integration of inorganic functional materials into large areas, 3D layouts for high throughput, and industrial-scale manufacturing using printing technologies.

Directly photopatternable interfaces are introduced that facilitate two-dimensional spatial control of block copolymer (BCP) orientation in thin films. Copolymers containing an acid labile monomer were synthesized, formulated with a photoacid generator (PAG), and coated to create grafted surface treatments (GSTs). These as-cast GST films are either inherently neutral or preferential (but not both) to lamella-forming poly(styrene-block-trimethylsilylstyrene) (PS-b-PTMSS). Subsequent contact printing and baking produced GSTs with submicron chemically patterned gratings. The catalytic reaction of the photoacid generated in the UV-exposed regions of the GSTs changed the interfacial interactions between the BCP and the GST in one of two ways: from neutral to preferential (“N2P”) or preferential to neutral (“P2N”). When PS-b-PTMSS was thermally annealed between a chemically patterned GST and a top coat, alternating regions of perpendicular and parallel BCP lamellae were formed.

Printing is a promising method for the large-scale, high-throughput, and low-cost fabrication of electronics. Specifically, the contact printing approach shows great potential for realizing high-performance electronics with aligned quasi-1D materials. Despite being known for more than a decade, reports on a precisely controlled system to carry out contact printing are rare and printed nanowires (NWs) suffer from issues such as location-to-location and batch-to-batch variations. To address this problem, we present here a novel design for a tailor-made contact printing system with highly accurate control of printing parameters (applied force: 0–6 N ± 0.3%, sliding velocity: 0–200 mm/s, sliding distance: 0–100 mm) to enable the uniform printing of nanowires (NWs) aligned along 93% of the large printed area (1 cm2). The system employs self-leveling platforms to achieve optimal alignment between substrates, whereas the fully automated process minimizes human-induced variation. The printing dynamics of the developed system are explored on both rigid and flexible substrates. The uniformity in printing is carefully examined by a series of scanning electron microscopy (SEM) images and by fabricating a 5 × 5 array of NW-based photodetectors. This work will pave the way for the future realization of highly uniform, large-area electronics based on printed NWs.

Microtransfer molding (µTM) and microcontact printing (µCP) techniques were demonstrated for the preparation of platinum based catalysts in hexagonally arranged patterns to achieve cathode catalyst layers (CCLs) with microscale patterned features. These soft lithographic techniques, previously demonstrated for use in the preparation of patterned thin films, were adopted to produce patterned CCLs for proton exchange membrane fuel cells (or PEMFCs) with features having a thickness up to 20 µm. The resulting CCLs contained precise microscopic patterns that could be tuned for improving the performance of PEMFCs. It was demonstrated that CCLs containing arrays of microscale, cylindrical holes as prepared by µTM exhibited an improvement in their water management characteristics within PEMFCs when compared to CCLs prepared from continuous catalyst films. Upon further tuning of the CCL transfer procedures for µCP of CCLs, the formation of isolated microscale, disc-like features were demonstrated to have twice the mass activity of that observed for PEMFCs containing CCLs with uniform thin catalyst films. These methods to prepare patterned CCLs are compatible with current manufacturing techniques and could be easily adapted to incorporate other catalyst materials for further improvements in PEMFC performance. The soft lithography techniques used herein could also be scaled up to meet the industrial demand of large volume manufacturing.

A novel platform of microfluidic paper-based analytical devices (μPADs) for dual detection of bisphenol A (BPA), a model analyte, was fabricated using an electronic digital plotter to create the stacked layer of μPADs and generate the lateral-flow channel without using an external pump. Two detection techniques, including electrochemical detection and laser desorption ionization mass spectrometric detection (LDI-MS), were used complementarily to improve the precision in the detection of BPA. The fluid sample was delivered to both detection zones by the capillary action, automatically generated from the fabricated microfluidic device. For an electrochemical sensor, two ballpoint pens filled with silver nanoparticles (AgNPs) and multiwall carbon nanotube (MWCNT) ink were used to print onto the paper with a contact printing method using a digital plotter. To further improve the sensitivity, zinc oxide (ZnO) was used to modify both electrochemical and LDI-MS detection zones. For BPA detection, high electrocatalytic properties and strong UV absorption of ZnO promote the electron transfer in the electrochemical sensor and ionization efficiency in LDI-MS with low interferences compared with a conventional organic matrix. Under optimal conditions, this platform showed a dual detection capability for BPA with a detection limit of 0.35 μM for electrochemical detection and with an ultralow detection limit of 0.01 pM for LDI-MS. This novel platform might be very useful for trace analyses requiring high precision detection of various analytes.

Highlights A dry transfer method for the mass production of transparent conductive carbon nanotube (CNT) films inspired by typography has been proposed.The strain sensors based on the CNT films have high stretchability and repeatability (gauge factor up to 9960 at 85% strain).These ultrathin strain sensors can detect human motion, sound, and pulse, suggesting promising application prospects in wearable devices. Electronic supplementary material The online version of this article (10.1007/s40820-019-0323-8) contains supplementary material, which is available to authorized users., Flexible and wearable sensing devices have broad application prospects in bio-monitoring such as pulse measurement, motion detection and voice recognition. In recent years, many significant improvements had been made to enhance the sensor’s performance including sensitivity, flexibility and repeatability. However, it is still extremely complicated and difficult to prepare a patterned sensor directly on a flexible substrate. Herein, inspired by typography, a low-cost, environmentally friendly stamping method for the mass production of transparent conductive carbon nanotube (CNT) film is proposed. In this dry transfer strategy, a porous CNT block was used as both the seal and the ink; and Ecoflex film was served as an object substrate. Well-designed CNT patterns can be easily fabricated on the polymer substrate by engraving the target pattern on the CNT seal before the stamping process. Moreover, the CNT film can be directly used to fabricate ultrathin (300 μm) strain sensor. This strain sensor possesses high sensitivity with a gauge factor (GF) up to 9960 at 85% strain, high stretchability (> 200%) and repeatability (> 5000 cycles). It has been used to measure pulse signals and detect joint motion, suggesting promising application prospects in flexible and wearable electronic devices. Electronic supplementary material The online version of this article (10.1007/s40820-019-0323-8) contains supplementary material, which is available to authorized users.

The handcrafted fabrication of a pyramidal mold on a silicon wafer for nanopatterning was investigated. This process started with the manual delivery of an aqueous glycerol solution onto the SiO2/Si wafer using a micropipette and subsequent drying to form a hemisphere whose diameter is in the range of hundreds of micrometers. A coating of polystyrene (PS) onto this wafer generates a circular hole caused by dewetting. Subsequently, anisotropic wet-etching with the PS film as a mask produces a pyramidal trench, whose apex approaches hundreds of nanometers. Various elastomeric materials were casted into this pyramidal mold. A pyramidal tip mounted on a simple micropositioner was used for electrochemistry and patterning of a protein. First, an agarose hydrogel was cast with a hydrogel pen for the electrochemical reaction (HYPER). The redox reaction at the HYPER-electrode interface demonstrated the characteristics of an ultramicroelectrode or bulk electrode based on the contact area. Second, the pyramidal polydimethylsiloxane served as a polymer pen for the contact printing of silane on a glass substrate. After the successive immobilization of biotin and avidin with fluorescence labeling, the resulting fluorescence image demonstrated the successful patterning of the protein. This new process for the creation of a pyramidal mold, referred to as a "do-it-yourself" process, offers advantages to nonspecialists in nanotechnology compared to conventional lithography, specifically simplicity, rapidity, and low cost.

Six high molecular weight, soluble, and stable elastomers were prepared derived from −O(CH2)3Si(CH3)3/–OCH2CF3 cosubstituted polyphosphazenes with 1–92 mol % of the organosilicon component. The surface and morphological properties are appropriate for biomaterials, soft contact printing, or other elastomeric applications. Full substitution by either side group yields thermoplastics. The syntheses were facilitated by small molecule model reactions to establish appropriate reaction conditions.

This paper reports the fabrication of subwavelength nano-structures on the curved surface of a glass lens for the purposes of anti-reflection. It utilizes a flexible PDMS mold to transfer metallic patterns to the lens surface which is pre-coated with a polymer layer. Using the transferred metal pattern as an etching mask, nano-structures are directly fabricated on the lens surface by plasma dry-etching processes. A plano/convex lens made of BK-7 glass with a lens diameter of 12.7 mm and a radius of curvature of 25.8 mm is used in this paper. Hexagonally arrayed nano-structures with a truncated conical profile, a center-to-center pitch of 300 nm, and a maximum structure height of 290 nm are experimentally achieved. Measurement results show the optical transmittance is increased by about 2.4% in average for wavelength within visible light spectrum. The directly fabricated nano-structures also exhibit good anti-glaring effects and the potentials for further optical applications.

Novel, printed contacts for single crystal CVD grown diamond particle detectors are reported. Silver contacts with guard-rings were formed by three-dimensional metal printing. The resulting devices exhibit similar properties to the current state-of-the-art diamond detectors employing carbide layer contacts, yet detectors with the printed contacts retain high charge collection efficiency even after exposure to 450 °C (unlike aluminum contact devices for instance). The printed silver contacts do not require high temperature annealing steps as carbide based contacts. The contact printing process is performed within a few minutes in ambient conditions. The novel printed contact method enables contact deposition without expensive vacuum equipment; furthermore, contact patterning can be designed and performed instantaneously, without design and fabrication of expensive photolithography masks and without the need for clean room facilities.

Contact printing of inorganic nanostructures such nanowires (NWs) has shown great potential for development of high-performance large area electronics (LAE) by printing. The LAE requires printing of electronic layer at selected locations, defined by the circuit layouts. In this paper, we demonstrate that simply with tailored surface morphology of the receiver substrate it is possible to obtain selective printing of electronic layers. The contact printing process has been used here to obtain NW (d=100nm) arrays on the receiver substrates, which is patterned with 3D features of varying height (20 – 200nm). The result show that for larger feature heights, the surface morphology has an impact on the printing uniformity. The effects of surface morphology are also studied in the context of multi-layer devices where uneven surfaces can be found. Surface planarization is investigated as a means for restoring the printing uniformity on uneven surfaces. The conducted studies demonstrate that surface features of a device can be exploited to aid in device fabrication while the planarization technique is able to negate unwanted effects resulting from uneven printing surfaces.

Background: Decomposing an observed variation in critical dimension (CD) into its sources of variation is an important analysis, but it is often tedious and prone to error. For EUV processes, identifying the magnitude of stochastic variations is especially important and relevant. Aim: An automated process for decomposing CD errors into its sources will aid in the analysis of a specific EUV process. Approach: MetroLER offline metrology software has been updated to perform automated sources of variation analysis, including the measurement and subtraction of systematic and random components, such as across-SEM-field signatures and random metrology errors. Results: For a staggered array of 24 nm contacts holes on an 80X46 nm pitch, the total CD uniformity (CDU) of about 3.3 nm included a global CDU across wafer of about 1.0 nm, a systematic mask contribution of 1.7 nm, systematic metrology contribution of 1.0 nm, and a random metrology contribution of 0.67 nm (all 3σ), leaving a stochastics-only CDU of about 2.6 nm. Conclusions: Careful consideration of the systematic and random components in CD measurement variations enables measurement of the stochastic contribution to a state-of-the-art EUV contact printing process. The contribution of metrology error

In August 1889, the Eastman Dry Plate Company made its first thin and flexible cellulose nitrate base on which to coat a light-sensitive emulsion for photographic film for its consumer snapshot cameras. Vicious nitrate dope was poured onto glass plates and when dry was peeled off as thin sheets, after which they were coated with photographic gelatin emulsion. Eastman intended that this flexible transparent film would replace the paper substrate stripping film used in his Kodak No. 1 camera of 1888. Stripping film, after removal from the customer’s camera at Rochester, was developed, and its image-bearing gelatin emulsion was stripped from the paper backing and laid onto a glass sheet for making contact prints. Modern photography was inaugurated with the new Eastman Transparent Film that made it far easier to make prints (Belton 1992). This product was exactly what Thomas Edison’s hands-on lab assistant William Kennedy Laurie Dickson needed for Kineto Project experiments. As recounted earlier in these pages, in a letter dated March 18, 1925, George Eastman wrote: “I received a call from a representative of Mr. Edison’s (probably Dickson) who told me of Mr. Edison’s experiments in motion pictures and how necessary it was for him to have some of this film.” (Richardson 1925) Dickson sent a $2.50 purchase order for a 1 in. wide strip of 50 feet of film, which Eastman received on September 2, 1899 (Bowen 1955). The film would be driven through experimental Kinetograph, and Kinetoscope machines after perforations were added in Dickson’s darkroom using a machine of his devising. Dickson had to make a decision about the direction of the film’s travel, horizontal or vertical; at first the film was horizontal-traveling, but Edison and Dickson settled on vertical-traveling 35 mm film cutdown from 70 mm stock.

Green electronics is an emerging environment-friendly process of the design and manufacture [...]

The ‘coffee stain ring’ is a particle deposit, that forms naturally, when the liquid of a suspension drop evaporates, leaving the particles at the edge of the deposit. Although observed in coffee cups in everyday life, such deposits appear in a wide range of liquid, particle and surface combinations and have attracted vivid research attention. Previous studies focused on the fluidics of evaporating suspension droplets on rigid materials, where the ring formation was shown to occur for pinned contact lines, and possible suppression of the coffee stain effect with surfactants, or other externally driven means, was investigated. Here, we show that, on soft materials, we can control the topography of the deposit on demand – promoting or suppressing the coffee ring effect – by simply changing the environmental humidity, regulating the evaporative flux. We perform particle tracking of droplets drying on soft substrates at varied environmental conditions and show with experimental observations and theoretical analysis that, at an expedited contact line velocity, particles are advected towards the receding contact line. We relate this advection to the viscous dissipation within the soft solid, retarding the contact line motion. The coffee ring formation in the presence of a receding contact line and its control by the environmental humidity, bring a new perspective to the conditions of the manifestation of this frequent deposit topography. We demonstrate the importance of our findings during the printing of a colloidal line, showing the ability to trigger line bifurcation on soft substrates by regulating the evaporative flux, introducing another degree of controllability for contact printing. ISSN:0022-1120 ISSN:1469-7645

Quasi-1D nanowires (NWs) have shown a great potential for the large-area flexible electronics due to their excellent electronic and optoelectronic properties and high mechanical flexibility. The growth of high-quality NWs often requires a high temperature process, which is incompatible with most of flexible substrates. In this regard, a printing strategy has been adopted to decouple the synthesis process from thermally sensitive polymeric substrates. This paper presents a detailed study on the selective printing of NWs using contact printing. In situ scanning electron microscope (SEM) characterizations have been employed here to illustrate the robustness of printed NWs after carrying out various standard microfabrication processes. This study improves our understanding of the NW printing process and lays a strong foundation for the realization of devices and systems such as electronic skin using the NW printing approach.

Radio frequency identification (RFID) is a well-established technology, which finds use in applications including inventory management, security, logistics, product marketing, as well as next generation flexible sensor platforms. Meanwhile, there is growing interest to use 2D materials like graphene in sensing due to its high surface to volume ratio, excellent electrical, mechanical and thermal properties. This paper capitalizes on the unique properties of graphene and ordinary fabrics and reports on the development of graphene textile-based RFID tags operating at 13.56 MHz for potential application in wearable and flexible electronics. Patterning of graphene on textile surfaces was achieved by low-cost technologies including spray, dispense and contact printing to yield circular and rectangular RFID tags with a maximum range of 3 cm and induced voltage of up to 78 mV peak-to-peak at an area of 18 cm2. Operation of the graphene textile RFID tags under different bending scenarios was tested to demonstrate the proof-of-concept in flexible and wearable sensing applications.

Printed electronics is a technology in which conductive ink or functional materials are printed as a flexible material passes between rolls. It is possible to apply various applications such as solar cell, sensor, and display, and it is the next generation process that can mass-produce eco-friendly within a short time. However, if the printing pressure between rolls cannot be made uniform in a roll-to-roll process, it is difficult to commercialize printed electronics due to the deterioration of print quality. In our previous work, initial conditions were selected using pre-measured roll shape information to minimize printing pressure variations, and the printing pressure unevenness due to repeated runout was reduced. In order to equalize the contact printing pressure, this paper designs a controller model similar to the half car model considering the relationship between the two servomotors of the two degree of freedom individual drive system and the pressures at both ends of the impression roll. In addition, the control system to uniform the contact printing pressure using the roll-to-roll two degree of freedom individual drive system was confirmed by simulation and experiment.

Printed electronics has attracted significant interest in recent years due to simple, cost-effective fabrication, reduced e-waste and potential for the development of multifunctional devices over large areas. Over the years, various printing technologies have been developed to pattern flexible surfaces to develop wide range of electronic devices. A large part of the research so far has focussed on organic semiconductors based devices, even if the modest performance they offer is insufficient for several emerging applications (e. g. internet of things (IoTs), smart cities, robotics, etc.) where fast computation and communication are required. The high-performance requirements could be addressed with printed devices from high-mobility materials such as single crystal silicon (Si) and graphene. This paper presents the printing methodologies (i.e. contact and transfer printing) that are being explored for highperformance devices and circuits using nano to macro scale structures such as semiconductor nanowires (NWs), nanoribbon (NR), and ultra-thin chips (UTCs) as well as graphene. Few examples of high-performance devices obtained using contact and transfer printing are also presented.

Graphene film materials have a wide range of applications. The accurate and non-destructive measurement of the sheet resistance plays an important role in the graphene application. The probe of traditional four-probe resistance measuring instruments is made of hard metal materials, which probably result in mechanical damage of graphene in the measurement processing. Besides, the accuracy and reproducibility are also poor. In this paper, conductive rubber was used as a probe due to their flexibility and conductivity. The mechanical damage of the probe to the graphene film and other film materials can be effectively avoided, and the repeatability and reproducibility of the sheet resistance measurement data can be obtained. This provides an alternative technique to measure the sheet resistance of fragile thin film materials.

We report a simple and reliable approach to fabricate composite hydrogel sheets with spatially patterned regions of plasmonic gold nanoparticles using a combination of contact printing and diffusion-controlled galvanic replacement reaction. In response to near-infrared laser irradiation, the localized increase in temperature induced the controlled shape deformation of the composite hydrogels, due to the combined effect of photothermal heating of the loaded gold nanoparticles and the thermal responsiveness of the hydrogel matrix. The same hydrogel can be designed to exhibit different modes of shape deformation depending on the direction of light irradiation, which has rarely been reported previously. The composite hydrogels may find applications in biomedicine and soft robots.

This paper presents a back-gated ZnO nanowires (NWs) field-effect transistor (FET) realized through the contact printing process. A low-stress $\mathbf{SiN}_{\mathbf{x}}$ deposited at room temperature by inductively coupled plasma (ICP) process was employed as the back-gate dielectric. Importantly, the adopted fabrication process evades any high-temperature process including for the deposition of the high-quality gate dielectric. The temperature fabrication is critical for development of electronic devices on flexible substrates. The ZnO NW FET shows excellent performance, which is reflected through transconductance (477 nS) and $\mathbf{I}_{\mathbf{on}}/\mathbf{I}_{\mathbf{off}}$ ratio $(\sim\mathbf{10}^{\mathbf{6})}$ . Finally, the developed ZnO NW FET was investigated for UV detection and it exhibited a gate tunable photoresponsivity.

Quasi-1D ZnO nanowire (NW) is one of the most promising materials for sensing applications because of its high surface to volume ratio and high sensitivity to external stimulus. Due to their low dimension nature, the NWs are also excellent candidates for flexible electronics. In this work, we used a printing method to achieve highly aligned ZnO NWs on polyimide substrate for flexible UV photodetector application. The as-fabricated devices shows high photo to dark current ratio up to 106 and exhibits a stable performance under extensive mechanical bending tests up to 1000 cycles. This work is believed to advance the research on large area flexible electronics.

A simple programmable contact printing method using ballpoint pens with silver nanoparticle (AgNP) and carbon nanotube (CNT) ink and a digital plotter were developed for quick patterning of electrodes on paper. This printing method enables sequential and programmable printing with two different inks and with ink consisting of high viscosity materials and is amenable to reproducibility of printed electrodes and customized designs. With this printing method, AgNP and CNT patterns with low electrical resistance and high density of the material can be printed. Using these AgNP and CNT inks, we fabricated disposable electrochemical sensors (ECSs) on paper. The ECSs were successfully used to detect glucose at various concentrations from 0 to 15 mM. The characteristics of the printed AgNP and CNT patterns, such as the printing resolution, surface morphology, and electrical properties, were also studied. The proposed contact printing method opens an avenue for printing paper-based electronics and devices.

The kinematics and dynamics of the vehicle, road safety depend on the interaction of the elastic wheel with the supporting surface. The paper analyzes the features of the elastic wheel of a car and identifies such indicators as the rolling resistance coefficient, the twisting angle of the tire body, the radius of the movement path, and the stabilizing torque of the tire. An inspection of recent studies and publications has been conducted, according to which it has been established that mathematical models that describe the interaction of a tire with a support surface exist only for the simplest case of movement i.e. straight-line motion along a solid surface at a fixed speed. As for the general case of movement, so that the movement along a curvilinear trajectory of a changeable radius of curvature with a changeable speed of movement; today there are no universal mathematical dependencies applicable to practical use. The definition of the twisting angle of the tire body and the lateral displacement of the unit wheel disc, as well as the lateral displacement of the wheels of the first and third axles of the three-axle bogie, which multiaxle trucks have (e.g. KraAZ-7140N6) or three-axle semi-trailers are considered in detail. Dependencies are presented for calculating the stabilizing moment of a tire, which is formed by such parameters as the angular stiffness of the tire relative to the vertical axis, the angle of withdrawal, the twisting angle of the tire, etc. The features of the portable and relative movement of the contact print of a tire during its rotation in place and during movement are determined depending on the design parameters, in particular, on the length of the hub. It was found out in which cases during the turn an additional roll of the steerable wheel occurs relative to the supporting surface. The results of these studies are useful for engineers and researchers who are working to improve the performance properties of vehicles.

Black phosphorus (BP) has distinctive properties of tunable direct band gap as a semiconductor material, and both high carrier mobility and on/off switching performance for electronic devices, but has a significant drawback of material degradation in ambient atmosphere. Also, unlike graphene or MoS2, BP is only synthesized in bulk shapes limiting the fabrication of thin film-based devices. We demonstrated a contact printing process for BP field effect transistors (FET) with the steps of mechanical exfoliation of BP flakes and their randomized stamping in dry-transfer regime. The contact printing featured by fast, continuous and solvent-free process on the pre-patterned electrodes guarantees high process efficiency providing immunity against the chemical degradation of BP layers. With asymmetric I-V characteristics, the resultant BP-channelized FET shows the electrical properties of on/off current ratio, hole mobility, and subthreshold swing as > 102, ~ 130 cm2/Vs, and ~ 4.6 V/dec, respectively.

Realizing high-performance electrochemical biosensors in a simple contact-printing-based approach significantly increases the applicability of integrated flexible biosensors. Herein, an enzyme-sticker-based approach that enables flexible and multielectrochemical sensors via simple contact-transfer printing is reported. The enzyme sticker consists of an enzymatic conductive network film and a polymeric support. The enzyme-incorporated nanostructured conductive network showing an efficient electrical coupling was assembled via the hydrodynamic layer-by-layer assembly of redox enzymes, polyelectrolytes, single-walled carbon nanotubes, and a biological glue material, M13 phage. The enzymatic conductive network on a polymeric membrane support was facilely wet contact-transfer printed onto integrated electrode systems by exploiting varying degrees of hydrophilicity displayed by the enzymatic electronic film, polymeric support, and receiving electrodes of the sensor system. The glucose sensors fabricated using the enzyme sticker detected glucose at a concentration of as low as 35 μM and showed high selectivity and stability. Furthermore, a flexible dual-sensor array capable of detecting both glucose and lactate was demonstrated using the versatile enzyme sticker concept. This work presents a new route toward assembling and integrating hybrid nanomaterials with efficient electrochemical coupling for high-performance biosensors and health-monitoring devices as well as for emerging bioelectronics and electrochemical devices.

Rapid progress in micro- and nanotechnologies such as lab-on-a-chip (microfluidic networks, sensors, actuators, and connectors), soft lithography (replica moulding, microcontact printing and affinity contact printing), and stretchable transparent electronics has strongly benefitted from high-performance polymers like poly(dimethyl)siloxane (PDMS) that are suited for high-fidelity microsystem construction and rapid prototyping. While basic PDMS has been a unique enabling material, recent progress in tailoring PDMS to specific requirements will render this material even more valuable in the future. Basic PDMS is elastic, transparent, biocompatible, gas-permeable, and forms conformal contact with surfaces. Surface modifications of PDMS, inducing properties such as hydrophilicity, electrical conductivity, anti-fouling, energy harvesting, and energy storage (supercapacitors) are of major interest. Bulk modifications can alter PDMS properties such as elasticity, electrical and thermal conductivity. Such bulk modified PDMS composite materials can be created by embedding free molecules (e.g., dyes), nanoparticles (graphene, carbon nanotubes, and various other of organic and inorganic nature) or microparticles, or by altering the composition of the prepolymers before polymerization. Both, surface and bulk modifications of PDMS open avenues to a multitude of tuneable characteristics optimized for a diverse set of applications ranging from integrated micro- (lab-on-a-chip) to macro-systems (biomedical devices and epidermal electronics). In microfluidic systems design exploiting modified PDMS, a key aspect of this review, the unique features of these materials permit rapid, easy, and reproducible construction without the need for elaborate facilities and trained personnel as compared to other materials like silicon. This review focuses on recent progress in modification strategies to alter deliberately PDMS surface and bulk properties, especially for microfluidic, biological, flexible electronics, e-skin, and self-healing applications.

Using molecular dynamics simulation, we study the thermal healing of a mixed-thiol monolayer grown by contact printing. By simulating the monolayers with various compositions of octadecanethiol and decanethiol molecules, we show that a mixed-thiol monolayer grown by contact printing contains a significant portion of unbound molecules which fail to bind their sulfur atoms to the underlying gold surface. A subsequent thermal annealing (300–370 K) however removes the unbound thiol molecules and gives an ordered and compact monolayer. We uncover the molecular pathways behind the removal of the unbound molecules during thermal annealing.

Herein, we developed an automated and flexible system for performing miniaturized liquid-liquid reactions and assays in the femtoliter to picoliter range, by combining the contact printing and the droplet-based microfluidics techniques. The system mainly consisted of solid pins and an oil-covered hydrophilic micropillar array chip fixed on an automated x- y- z translation stage. A novel droplet manipulation mode called "dipping-depositing-moving" (DDM) was proposed, which was based on the programmable combination of three basic operations, dipping liquids and depositing liquids with the solid pins and moving the two-dimensional oil-covered hydrophilic pillar microchip. With the DDM mode, flexible generation and manipulation of small droplets with volumes down to 179 fL could be achieved. For overcoming the scale phenomenon specially appeared in picoliter-scale droplets, we used a design of water moat to protect the femtoliter to picoliter droplets from volume loss through the cover oil during the droplet generation, manipulation, reaction and assay processes. Moreover, we also developed a precise quantitative method, quantitative droplet dilution method, to accurately measure the volumes of femtoliter to picoliter droplets. To demonstrate its feasibility and adaptability, we applied the present system in the determination of kinetics parameter for matrix metalloproteinases (MMP-9) in 1.81 pL reactors and the measurement the activity of β-galactosidase in single cells (HepG2 cells) in picoliter droplet array. The ultrasmall volumes of the droplet reactors avoided the excessive dilution to the reaction solutions and enabled the highly sensitive measurement of enzyme activity in the single cell level.

In this work, we evaluate a novel jetink printing method with silver nano particle ink for fabrication of metal–semiconductor–metal structures based on Cd 1 − x Zn x Te for gamma-ray detector applications. Contact printing technology offers several advantages in terms of infrastructure and prototype cycle time. For comparison and reference similar samples with thermally evaporated silver and indium contacts were processed and analyzed. The MSM devices were investigated by various static and dynamic characterization methods including current–voltage (I–V), power spectral density of noise (PSD), transient current technique (TCT), and gamma-spectroscopy. In addition, impact of thermal annealing up to 200 °C was studied. The devices with the printed contacts exhibit comparable performance with the reference benchmark detectors. Preliminary study indicate that the printed contacts are immune to moderate thermal treatment, and moreover, show signs of improvement with annealing.

Poly-dimethylsiloxane (PDMS) is known to provide ubiquitous platform for micro Total Analysis System (μ-TAS) and Lab-On-Chip (LOC) development. Although soft lithography is extensively accepted as a fabrication tool for PDMS, direct write lithography techniques also have drawn considerable attention due to some of its own advantages. Even though e-beam lithography in PDMS is reported previously, the present manuscript reveals establishment of doped PDMS as a positive tone, self-standing and self-developable resist platform for 6 MeV e-beam lithography in normal ambience. For microstructures fabrication, undoped PDMS and photoinitiator doped PDMS as resist materials are processed using contact printing mode lithography with use of the mask containing array of circles on it. Effects of lithography processing parameters on various resist compositions are investigated to achieve improved geometry and surface profile of the fabricated microstructures. Lithographic investigations on the undoped PDMS shows microstructures with sloppy sidewalls depicting inverted bell shape geometry and cone like nanostructures inside it deteriorating surface profile. Whereas in case of doped PDMS cone like nanostructures are completely vanished and inverted bell shape geometry transformed into clean and uniform concave shape profile, which is then identified as finely produced micro lens array (MLA). The lensing quality of MLA is tested and the images produced by MLA are clear and uniform in size and shape, which confirms formation of microlenses accountable as an optical component in many applications. The observed concave geometry of fabricated MLA is resulted out of energy gradient generated during the e-beam exposure of resist stamp through mask. Similarly, an electrostatic interaction is recognized as governing mechanism for e-beam interaction with PDMS. Photoinitiator plays crucial role in energy absorption and distribution which resulted in seamless control over formation of lateral and vertical dimensions thereby giving optical smoothness to surface of MLA. The optimized lithographic parameters and composition of the resist platform, can be used to fabricated MLA with fine imaging quality and desired location of focal plane according to demand of application.

Multiprotein micropatterning allows the creation of complex, controlled microenvironments for single cells that can be used for the study of the localized effects of various proteins and signals on cell survival, development, and functions. To enable analysis of cell interactions with microprinted proteins, the multiprotein micropattern must have low cross-contamination and high long-term stability in a cell culture medium. To achieve this, we employed an optimized plasma ion immersion implantation (PIII) treatment to provide polystyrene (PS) with the ability to covalently immobilize proteins on contact while retaining sufficient transparency and suitable surface properties for contact printing and retention of protein activity. The quality and long-term stability of the micropatterns on untreated and PIII treated PS were compared with those on glass using confocal microscopy. The protein micropattern on the PIII treated PS was more uniform and had a significantly higher contrast that was not affected by long-term incubation in cell culture media because the proteins were covalently bonded to PIII treated PS. The immunostaining of mouse pancreatic β cells interacting with E-cadherin and fibronectin striped surfaces showed phosphorylated paxillin concentrated on cell edges over the fibronectin stripes. This indicates that multiprotein micropatterns printed on PIII treated PS can be used for high-resolution studies of local influence on cell morphology and protein production.

Self-assembly of colloidal nanospheres combined with various nanofabrication techniques produces an ever-increasing range of two-dimensional (2D) ordered nanostructures, although the pattern periodicity is typically bound to the original interparticle spacing. Deformable soft lithography using controlled deformation of elastomeric substrates and subsequent contact printing transfer offer a versatile method to systematically control the lattice spacing and arrangements of the 2D nanosphere array. However, the anisotropic nature of uniaxial and biaxial stretching as well as the strain limit of solvent swelling makes it difficult to create well-separated, ordered 2D nanosphere arrays with large-area hexagonal arrangements. In this paper, we report a simple, facile approach to fabricate such arrays of polystyrene nanospheres using a custom-made radial stretching apparatus. The maximum stretchability and spatial uniformity of the poly(dimethylsiloxane) (PDMS) elastomeric substrate is systematically investigated. A pitch increase as large as 213% is demonstrated using a single stretching-and-transfer process, which is at least 3 times larger than the maximum pitch increase achievable using a single swelling-and-transfer process. Unlike the colloidal arrays generated by the uniaxial and biaxial stretching, the isotropic expansion of radial stretching allows the hexagonal array to retain its original structure across the entire substrate. Upon radial strain applied to the PDMS sheet, the nanosphere array with modified pitch is transferred to a variety of target substrates, exhibiting different optical behaviors and serving as an etch mask or a template for molding.

ZnO thin-film transistors (TFTs) with scaled channel lengths of 10 μ m, 5 μ m, 4 μ m, and 2 μ m exhibit increasing intrinsic channel electron mobility at a gate bias of 10 V (15 V) from 0.782 cm2/Vs (0.83 cm2/Vs) in the 10 μ m channel length TFT to 8.9 cm2/Vs (19.04 cm2/Vs) for the channel length scaled down to 2 μ m. Current-voltage measurements indicate an n-type channel enhancement mode transistor operation, with threshold voltages in the range of 8 . 4 V to 5 . 3 V, maximum drain currents of 41 μ A/ μ m, 96 μ A/ μ m, 193 μ A/ μ m, and 214 μ A/ μ m at a gate bias of 10 V, and breakdown voltages of 80 V, 70 V, 62 V, and 59 V with respect to channel lengths of 10 μ m, 5 μ m, 4 μ m, and 2 μ m. The channel electron mobility (excluding contact resistance) is extracted by the transmission line method (TLM) from the effective electron mobility (including contact resistance). The contact sheet resistance of 4 . 6 × 10 5 Ω /sq extracted from the measurements, which is 3.5× larger than the contact sheet resistance of 1 . 3 × 10 5 Ω /sq obtained from the DFT calculation and the 1D self-consistent Poisson-Shrodinger simulation, largely limits the drive current in the scaled ZnO TFTs.

We demonstrate the utility of non-contact printing to fabricate the mAST&mdash, an easy-to-operate, microwell-based microfluidic device for combinatorial antibiotic susceptibility testing (AST) in a point-of-care format. The wells are prefilled with antibiotics in any desired concentration and combination by non-contact printing (spotting). For the execution of the AST, the only requirements are the mAST device, the sample, and the incubation chamber. Bacteria proliferation can be continuously monitored by using an absorbance reader. We investigate the profile of resistance of two reference Escherichia coli strains, report the minimum inhibitory concentration (MIC) for single antibiotics, and assess drug&ndash, drug interactions in cocktails by using the Bliss independence model.

Patterning materials with different properties in a single film is a fundamental challenge and essential for the development of next-generation (opto)electronic functional components. This work introduces the concept of ion exchange lithography and demonstrates spatially controlled patterning of electrically insulating films and semiconductors with tunable optoelectronic properties. In ion exchange lithography, a reactive nanoparticle “canvas” is locally converted by printing ion exchange “inks.” To demonstrate the proof of principle, a canvas of insulating nanoporous lead carbonate is spatioselectively converted into semiconducting lead halide perovskites by contact printing an ion exchange precursor ink of methylammonium and formamidinium halides. By selecting the composition of the ink, the photoluminescence wavelength of the perovskite semiconductors is tunable over the entire visible spectrum. A broad palette of conversion inks can be applied on the reactive film by printing with customizable stamp designs, spray-painting with stencils, and painting with a brush to inscribe well-defined patterns with tunable optoelectronic properties in the same canvas. Moreover, the optoelectronic properties of the converted canvas are exploited to fabricate a green light-emitting diode (LED), demonstrating the functionality potential of ion exchange lithography.

A simple way for high-performance planar Si-PEDOT:PSS hybrid solar cells have been demonstrated in this work. Contact-printed, hydrophobically-recovered ultrathin siloxane layer has been employed as insertion layers at interfaces in Si-PEDOT:PSS hybrid solar cells. The printing has been done at room ambient in dry state for 510min, which has led to 13% cell efficiency with non-textured planar Si substrate. Interestingly, the layer has been found to be equally effective at both interfaces (top interface between Si and PEDOT:PSS, and bottom interface between Si and bottom electrode), while other insertion layers suggested in literature works at one interface only. Furthermore, the sheet resistance of PEDOT:PSS layer, rather than resistivity or conductivity, has been found to be the relevant characteristics in the hybrid solar cells, because the carrier conduction in 2-dimension is utmost importance in such devices. The suggested method can be a valuable help for low-cost, high-performance Si-PEDOT:PSS hybrid solar cells and can expedite the commercialization of the hybrid photovoltaics in near future. Display Omitted Above 13% efficiency for planar Si-PEDOT:PSS hybrid solar cell has been demonstrated.Sheet resistance of PEDOT:PSS layer has been found to be of primary importance for the cell.Printed ultrathin siloxane layer at interfaces enhanced the cell efficiency by suppressing carrier recombination.

A direct printing of liquid droplet matrix on various surfaces is demonstrated using a stamp that can be recycled for over 100 times. The technique can be applied to pattern functional organic materials and nanoparticles and fabricate microlens arrays in one step. By controlling the printing pressure and the surface wettability, a feature size that is smaller than that of the stamp was achieved in a tunable manner.

Contact printing of Quantum Dot (QD) and organic polymer (OP) composites is explored as an alternate method of fabricating a cross-reactive chemical sensor array. Sensing layers fabricated by inkjet printing and contact printing methods are compared, showing that contact printing methods demonstrate a more uniform distribution of the QDs and higher signal to noise ratios (SNRs) when exposed to chemical vapors. A cross-reactive array was then fabricated with CdSe QDs and five OPs and exposed to the vapor of 15 common laboratory solvents. Principal component analysis (PCA) of the data showed high dimensionality of the sensor array response and linear discriminant analysis (LDA) produced correct classification of the target analytes in 100% of test cases.

Wrinkling of thin films in micro- and nanoscale has found wide applications in stretchable electronics, optical gratings, material characterization, and biology. However, most wrinkling work is in planar fashion and only limited work on 3D wrinkling has been reported. In this paper, we present experimental demonstration of 3D Cr film wrinkling on PDMS micro-ridges induced by strain mismatch. We first fabricated PDMS micro-ridges using replication from a silicon mold, prepared by conventional microfabrication processes. While pre-stretching the PDMS specimen along the ridge direction, thin Cr film was deposited through physical sputtering. After releasing the prestrain, two wrinkling waves formed on the two inclined surfaces of the PDMS ridges with the same wavelength but opposite phases. These two wrinkling waves twist the top of the ridge into a wavy shape, forming wrinkling waves oscillating in the direction parallel to the substrate plane. In contrast, 2D wrinkling waves oscillate in the direction perpendicular to the substrate plane. Using finite element simulations, we demonstrate that the 180° phase shift between the two sides is favored by the dominant buckling modes. While the 3D wrinkling wavelength is consistent with 2D theoretical prediction, wrinkles on the ridge feature non-uniform wrinkling wave amplitude along the width of the inclined surface. This 3D wrinkling work opens new opportunities in manufacturing curved-shape mold for contact printing and increases surface to volume ratio for wetting and battery applications.

We report a novel and simple method to fabricate a high-sensitivity fully nanostructured photodetector by using CdS nanotubes (NTs) aligned arrays as active layer and Ag nanowires (NWs) transparent film as electrodes. The assembly of highly ordered and aligned CdS NTs arrays is obtained by a simple modified contact printing process. A fully nanostructured photodetector is fabricated by transferring the electrodes produced by Ag NWs network on the aligned CdS NTs arrays substrate, such that the aligned CdS NTs arrays as active layer are in contact with Ag NWs network as transparent electrodes. The resulting photodetector exhibits lower dark currents (

The structural and thermal properties of the nanometer-wide lines of a self-assembled monolayer (SAM) were investigated using molecular dynamics simulations. When grown by contact printing, a linear SAM contained a significant portion (8%) of unbound molecules that are inverted among upright molecules. This paper proposes thermal annealing (300–400 K) as an efficient method to remove the unbound molecules and improve the quality of the linear SAM. The partial melting of the SAM during heating enabled the unbound molecules to flip and adsorb. With subsequent cooling, the linear SAM recovered its compact ordered structure. The molecular mechanisms and activation energies involved in the thermal annealing were elucidated.

This work introduces photography-based photometry, as complementary to digital image colorimetry, by demonstrating that historical photography can be repurposed to enable UV photometric analysis, using inexpensive and ubiquitous materials. Analysis is performed by illuminating the samples with UV radiation and then capturing the transmitted irradiation on the surface of a photographic paper through photochemical reduction of its photosensitive coating. A visible image is then formed on the paper surface and is recorded as a digital photograph. The color intensity of the image is directly proportional to the concentration of the analytes in the sample and is quantified in the RGB color system. By selecting the appropriate light source and photosensitive paper, sensitivity to light can be selected to approximate the absorbance spectra of the target analyte thus accomplishing good selectivity and high sensitivity. On the basis of this principle, a variety of assays were used to demonstrate that photography-based photometry, can be used to perform accurate UV absorbance measurements over a wide spectral range, in a high throughput format (i.e. microtiter plates) and at low cost as compared to expensive microplate spectrophotometers. Depending on the photosensitivity of the photographic paper, linear ranges and detection limits that are similar or lower up to an order of magnitude to those obtained with standard spectrophotometry were achieved. Importantly, a single device configuration can be used for all assays, irrespectively of the maximum absorbance wavelength, which significantly simplifies its operation thus holding great promise for routine applications in resource-limited settings even by non-experts.

The incorporation of organic polymeric materials into chemical sensors and electro-optic devices has the potential to greatly advance these fields. A major challenge to their incorporation is the fabrication of thin films due to their intolerance of thermal deposition methods and solvent compatibility challenges. Here, a method for contact printing of quantum dot (QD) and organic polymer (OP) composites for the production of thin-film chemical sensors is described. The method described here allows for the repeatable, low-cost, and relatively simple production of thin films of QD/OP composites for use in chemical sensor arrays by a dry transfer process of the polymer on an elastomer stamp to the sensor substrate.

A simple method for fabricating a liquid metal (LM) pattern on a polydimethylsiloxane substrate through the process of contact printing is introduced in this paper. This material is easily oxidized when it is exposed to air; consequently, it is difficult to manipulate. Contact printing is a fabrication process based on an adhesive force between interfaces. Adhesion is enhanced by forming a new oxide layer; thus, the LM film on a flat mold is transferred to another mold by contact printing. Electrical conductivity of the transferred LM is 1.93 × 106 S/m, which is sufficiently high for its usage as an electrode in electric circuits. The resolution of the LM pattern can be controlled at ~20 μm and a complex pattern can be fabricated. Furthermore, the LM is semi-transparent and it is visually imperceptible when observed from a distance. Using the semi-transparent LM electrode, a LM triboelectric nanogenerator is fabricated. The device demonstrates normal performance as an energy harvesting system; consequently, the LM patterned by contact printing can be applied to wearable self-powered electronics.