The rheological properties of silver inks are analyzed, and the printing results are presented based on the inks and roll-to-roll printing speed. The shear viscosity, shear modulus, and extensional viscosity of the inks are measured using rotational and extensional rheometers. The inks exhibit the shear thinning power law fluids because the concentration of dispersed nanoparticles in the solvent is sufficiently low, which minimizes elasticity. After the inks are printed on a flexible substrate through gravure printing, the optical images, surface profiles, and electric resistances of the printed pattern are obtained. The width and height of the printed pattern change depending on the ink viscosity, whereas the printing speed does not significantly affect the widening. The drag-out tail is reduced at high ink viscosities and fast printing speeds, thereby improving the printed pattern quality in the roll-to-roll process. Based on the results obtained, we suggest ink and printing conditions that result in high printing quality for complicated printings, such as overlay printing registration accuracy, which imposes pattern widening and drag-out tails in printed patterns.
We study particle dynamics in drying colloidal solutions using the numerical simulation with discrete particle method (DPM). Simulations of two different systems were conducted; the drying dynamics of monodispersed and binary mixture of colloidal solution, and compared with those from the previous studies. In the monodispersed colloidal solution, the time evolution of particle concentration profile for varying Péclet number was simulated with the same initial particle concentration. In the binary colloidal solution, when the particle size ratio α is 3, three different stratification modes were observed varying Péclet number and initial particle concentration. By comparison, our method was in a good agreement with the existing methods. Additionally, because of the mesh-based Eulerian approach in our model, other various multi-physical phenomena, such as effect of thermal Marangoni or chemical reaction, can be included in an easy way. From the results, we expect that this work can provide a physical insight for predicting the quality of colloidal drying in a complicated situation.
Printed electronics have been considered to bring about the ICT (Information Communication Technology) revolution. The high-throughput production of the ultra-low-cost printed devices along with the level of integration of logic gates via an all roll-to-roll (R2R) printing method has been the major axes in the revolution. However, there have been certain concerns related to the integration of logic gates via the R2R printing methods. This review paper focuses on the key issues that must be resolved to maintain a uniform threshold voltage (V
th) value, which can otherwise impede the commercial viability of such devices. Amongst the various factors contributing to the ΔV
th value, the ink rheology, web handling, and the disparity in alignment amongst the drain-source electrodes and the gate electrodes due to the limitations of an overlay printing registration accuracy (OPRA) were reviewed to effectively control the variations during the R2R printing process, without including the material’s intrinsic instability factors. Accordingly, a unique design rule for the R2R printing foundry concept was introduced for manufacturing the devices with the available integration level of the logic gates, incorporating the printing parameters including ink rheology, ink transfer, web handling, and OPRA.
Extensive research is focused on the development of highly sensitive, rapid on-site diagnostic devices. The lateral flow strip (LFS) is a paper-based point-of-care diagnostic device, which is highly promising because of its ease of use and low cost. Despite these advantages, LFS device is still less popular than other methods such as enzyme-linked immunosorbent assay (ELISA) or real-time polymerase chain reaction (qPCR) due to its low sensitivity. Here, we have developed a fluorescence-based lateral flow strip (f-LFS) device for DNA detection using a molecular beacon (MB), a short hairpin-forming DNA strand tagged with a fluorophore-quencher pair. Each paper and membrane component of f-LFS device was carefully selected based on their physicochemical properties including porosity, surface functionality, and autofluorescence. The limit of detection (LOD) of this device was substantially improved to 2.1 fg/mL by adding MgCl2 to the reaction buffer and narrowing the test membrane dimension. Also, a portable fluorescence detection system for f-LFS was developed using a multi-pixel photon counter (MPPC), a sensitive detector detecting the signal on site. We anticipate that this highly sensitive paper-based diagnostic device can be utilized for on-site diagnosis of various diseases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.