Soluble Metal Oxo Alkoxide Inks with Advanced Rheological Properties for Inkjet-Printed Thin-Film Transistors

Effect of Polyol Molecular Structure on Fluidity, Surface Tension, and Printed Pattern Sharpness of Disperse Dye Inks

In the present study, density functional theory (DFT) has been used in simulating and calculating the molecular geometries of differently structured polyols (within a water phase), as well as the weak interactions between these polyols and the water molecules. Furthermore, low field nuclear magnetic resonance (LF-NMR) has been used in studying the transverse relaxation times of different polyols, in addition to their (20.00 wt %) fluidity in an aqueous environment. Moreover, the influence of polyols, with different molecular structures, on the ink fluidity, was also explored. A bubble pressure tensiometer was also used to characterize the surface tension of the aqueous polyol (20.00 wt %) solution, the sodium dodecyl sulfate (SDS, 0.50 wt %) solution, and the ink. This was made to clarify the influence of polyol and SDS on the surface tension of ink. In addition, the particle size, zeta potential, pH value, viscosity, and rheological properties of the ink, were also investigated. The resulting data showed that polyols have certain effects on the particle size, stability, and viscosity of the ink. The jetting performances of different polyol inks were, under certain conditions of the inkjet drive waveform, also explored. The results showed that the fluidity, viscosity, and surface tension of the ink will render a certain influence on the inkjet performances. The prepared polyol ink was thereafter used for polyester fabric printing, and the contour sharpness and color fastness of the printed fabric were accordingly evaluated. The data showed that the increase in ink viscosity, and decrease in fluidity, promote the improvement in contour sharpness. In addition, the printed fabric demonstrated an excellent color fastness.

Numerical Analysis of Droplets from Multinozzle Inkjet Printing

Multinozzle printing processing with the fabrication of a functional material film lays the foundation for the development of efficient scale production of a photoelectric device. However, a prominent challenge is how to realize the volume uniformity of the droplets. Here, a classical analysis method is introduced first by printing poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) to analyze the behavior of droplets. It relies on a variance calculation for the clarification of the law of implicit behavior of droplets in terms of digitizing. This method reveals the effect of printing parameters on the uniformity of the volume of droplets in multinozzle printing. Overall, by combining both ink formulations and printing parameter optimization, it is concluded that the minimum volume variance of nozzles with different numbers is less than 0.5% and the influence of various parameters in multinozzle printing is found to be ranked. The feasibility of this analysis method is presented and is of great significance to achieving a very stable, large-scale multinozzle printing device.

Solution-processed metal-oxide thin-film transistors: a review of recent developments

Driven by the rapid development of novel active-matrix displays, thin-film transistors (TFTs) based on metal-oxide (MO) semiconductors have drawn great attention during recent years. N-type MO TFTs manufactured through vacuum-based processes have the advantages of higher mobility compared to the amorphous silicon TFTs, better uniformity and lower processing temperature compared to the polysilicon TFTs, and visible light transparency which is suitable for transparent electronic devices, etc. However, the fabrication cost is high owing to the expensive and complicated vacuum-based systems. In contrast, solution process has the advantages of low cost, high throughput, and easy chemical composition control. In the first part of this review, a brief introduction of solution-processed MO TFTs is given, and the main issues and challenges encountered in this field are discussed. The recent advances in channel layer engineering to obtain the state-of-the-art solution-processed MO TFTs are reviewed and summarized. Afterward, a detailed discussion of the direct patterning methods is presented, including the direct photopatterning and printing techniques. Next, the effect of gate dielectric materials and their interfaces on the performance of the resulting TFTs are surveyed. The last topic is the various applications of solution-processed MO TFTs, from novel displays to sensing, memory devices, etc. Finally, conclusions are drawn and future expectations for solution-processed MO TFTs and their applications are described.

Hand-Fabricated CNT/AgNPs Electrodes using Wax-on-Plastic Platforms for Electro-Immunosensing Application

Fabrication of inexpensive and flexible electronic and electrochemical sensors is in high demand for a wide range of biochemical and biomedical applications. We explore hand fabrication of CNT modified AgNPs electrodes using wax-on-plastic platforms and their application in electrochemical immunosensing. Wax patterns were printed on polyethylene terephthalate-based substrates to laydown templates for the electrodes. Hand painting was employed to fabricate a silver conductive layer using AgNPs ink applied in the hydrophilic regions of the substrate surrounded by wax. CNT was drop cast on top of the working electrodes to improve their electrochemical signal. The device layers were characterized by scanning electron microscopy. The electrochemical performance of the hand fabricated AgNPs and CNT/AgNPs electrodes was tested using cyclic voltammetry, differential pulse voltammetry, and amperometry. The electrochemical response of CNT/AgNPs electrodes was relatively faster, higher, and more selective than unmodified AgNPs sensing electrodes. Finally, the hand-painted CNT/AgNPs electrodes were applied to detect carcinoembryonic antigen (CEA) by measuring the end-product of immunoassay performed on magnetic particles. The detection limit for CEA was found to be 0.46 ng/mL.

Influence of Local Heating on Marangoni Flows and Evaporation Kinetics of Pure Water Drops

The effect of localized heating on the evaporation of pure sessile water drops was probed experimentally by a combination of infrared thermography and optical imaging. In particular, we studied the effect of three different heating powers and two different locations, directly below the center and edge of the drop. In all cases, four distinct stages were identified according to the emerging thermal patterns. In particular, depending on heating location, recirculating vortices emerge that either remain pinned or move azimuthally within the drop. Eventually, these vortices oscillate in different modes depending on heating location. Infrared data allowed extraction of temperature distribution on each drop surface. In turn, the flow velocity in each case was calculated and was found to be higher for edge heating, due to the one-directional nature of the heating. Additionally, calculation of the dimensionless Marangoni and Rayleigh numbers yielded the prevalence of Marangoni convection. Heating the water drops also affected the evaporation kinetics by promoting the "stick-slip" regime. Moreover, both the total number of depinning events and the pinning strength were found to be highly dependent on heating location. Lastly, we report a higher than predicted relationship between evaporation rate and heating temperature, due to the added influence of the recirculating flows on temperature distribution and hence evaporation flux.