Printing and patterning system


Liquid transfer analysis for contact printing process


-      Objective

      Experimental investigations of the liquid transfer between two separating plates have been carried out, with the aim of increasing the ink transfer ratio in micro-gravure-offset printing.


Typical contact printing System (micro gravure offset printer)



Liquid transfer between two separating plates experiment

      -       Droplet separation process


-       Experimental setup


-       Results

(a) droplet filament between the upper plate and the lower plate, (b) captured image of a satellite droplet.


       Variation of the transfer ratio with the surface contact angle


       Transfer ratio for =



      Sequential pictures of droplet separation between two parallel plates with = 45o and (a) = 78o, (b) = 50o, (c) = 45o






Simulation of ink transfer for micro-gravure-offset printing


-      The micro-gravure-offset printing technique has recently received much attention as a potential method for the cost-effective mass-production of micro-scale electrical circuits.

-      Ink transfer between two parallel separating plates and between a trapezoidal cavity and an upward moving plate are simulated, as models of the printing of ink from the offset pad onto the substrate and the picking up of ink from the gravure plate by the offset pad, respectively.




Schematic of gravure-offset printing



Computational model


Instantaneous contours of the volume fraction of the liquid between two parallel plates




Transfer ratio of the liquid between two parallel plates




Instantaneous contours of the volume fraction of the liquid between cavity and plate




Variations of the final width of liquid on the upper plate (a) and the maximum cut height (b) as functions of and .






Animations of ink transfer process





Printed electronics on microstructured surface

-       Microstructured surface

(a) Geometry of the microstructured surface and (b) the unit cube.

-       Contact angle of conductive silver ink droplet on microstructured surface

Variations of the contact angle as a function of gap

-       Screen printing with conductive silver ink

(a) Schematic diagram of the screen-printing process, (b) geometry of the test pattern and (c) test patterns.


-       Printed conductive line pattern on microstructured surface

Images showing the printed patterns.


-       Printability



Variations in the printability as a function of linewidth for various gap distances




Direct micro/nano imprinting


-       Schematic diagram of QD direct micro/nano imprinting


  1)       the substrate (e.g., Si/SiO2 wafer) was cleaned with acetone and isopropanol and then  dried with N2 gas. The QD solution was dispensed onto the Si/SiO2 wafer.

2)       The solution was squeezed into a PDMS mold at low temperatures (80 C) and low pressures

3)       The Si/SiO2 wafer was heated at 80 C for 20 min to allow the QDs to form structures and to evaporate the solvent.

4)       After the substrate was cooled to room temperature, the PDMS mold was carefully removed from the substrate to leave an imprinted QD pattern.



-       Multiple colored QD patterning in the large area/ QD structure array  

1)     Fluorescence images of imprinted CdSe QD patterns

Circular or circle shaped dot arrays of multiple colored (red, green and blue) emitting

2)     The circle shaped/ donut shaped microdot (SEM and confocal image)



-       Multilayered and multicolored QD patterns by self-alignment  


(iiii) Direct imprinting of cylindrical red QD patterns on the first layer and an imprinted red QD SEM picture (inset). (iv) Subsequent PVP deposition and cross-linking at 150 C on the imprinted red QD patterns. (vvii) Green QD direct imprinting on top of the PVP/cylindrical red QD patterns. Note that the second PDMS mold is flat, whereas the first PDMS mold has the target patterns