Monolayer assisted LIFT printing of nanodroplets
Laser-induced forward transfer (LIFT) is a direct-write technique for printing materials through the thrust provided by an irradiating laser pulse . Because of its simplicity and flexibiltiy over the years this technique has been used for a broad range of applications such as organic electronics, biosensors, intergrated optics and plasmonics.
Serial printing of nanodroplets using conventional LIFT technique needs stringent conditions like tight focusing of the incident laser beam using high NA objective lenses and expensive fs lasers with smaller heat affected zones. This project will focus on printing of metallic nano-droplets using the LIFT technique in assistance with microspheres (Fig. 1). The microsphere when irradiated with the laser pulse focuses and enhances the field intensity just beneath the sphere which in turn provides the push to print nanodroplets onto another receiver substrate. Compared to the conventional method the proposed technique has several advantages such as parallel printing of thousands of dots in single shot, much lower transfer threshold and smaller printed features.
Figure 1: Schematic depicting monolayer assisted LIFT
 Bohandy, et al.,“Metal deposition from a supported metal film using an excimer laser”, J. Appl. Phys., Vol. 60 (4) (1986).
The main aim of the work is to investigate in detail the microsphere-assisted LIFT of metal nano-dots. The project will focus on the following two main areas:
1) Optimization of the key parameters (Surface pressure, pull speed, concentration, particle surface functionalization) for fabricating monolayers based on polystyrene and silica spheres of different diameters using Langmuir Blodgett (LB) method (Fig. 2) onto glass and quartz substrates.
2) LIFT printing of metallic nano-dots employing the monolayer coated samples with the microspheres acting as focusing elements. This will involve optimization of printing parameters (fluence, wavelength, ambient pressure, metal film thickness, distance between the donor and the acceptor substrate).
Figure 2: Illustration of LB method for monolayer fabrication.
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