Laser-induced forward transfer (LIFT) has demonstrated its ability for high resolution printing of a large set of materials in solid or liquid phase. The typical dimension of the LIFT-printed structures is of few micrometers. By downscaling the donor film thickness together with the pulse duration and the spot size of the laser, sub-micrometers metal droplets have also been printed. Recently, we have proposed the double pulse LIFT process (DP-LIFT) which relies on the use of two laser beams to transfer metal droplets in liquid phase from a solid donor thin film. First, a quasi-continuous wave laser irradiates the thin metal donor film to locally form a liquid film, then, a second short pulse laser irradiates this area to induce the formation of a liquid jet and the printing of a small droplet on the receiver substrate.
We used time-resolved shadowgraphy to investigate the dynamics of high-velocity nanojets generated from solid copper ﬁlms. These experiments show that this DP-LIFT approach induces the formation of very thin and stable liquid jets that expands over distances of few tens of micrometers for a large range of process conditions. We also demonstrated that the size of the melted metal pool plays an important role in the jet dynamics and allows controlling the size of the printed droplets. This process has been used to print 2D and 3D structures with micro and nano-meter sizes while avoiding the generation of any debris and these results demonstrates the high potential of DP-LIFT as a digital nano-printing process.
The development of organic electronic requires a non contact digital printing process. The European funded e-LIFT project investigated the possibility of using the Laser Induced Forward Transfer (LIFT) technique to address this field of applications. This process has been optimized for the deposition of functional organic and inorganic materials in liquid and solid phase, and a set of polymer dynamic release layer (DRL) has been developed to allow a safe transfer of a large range of thin films. Then, some specific applications related to the development of heterogeneous integration in organic electronics have been addressed. We demonstrated the ability of LIFT process to print thin film of organic semiconductor and to realize Organic Thin Film Transistors (OTFT) with mobilities as high as 4 10-2 cm2.V-1.s-1 and Ion/Ioff ratio of 2.8 105. Polymer Light Emitting Diodes (PLED) have been laser printed by transferring in a single step process a stack of thin films, leading to the fabrication of red, blue green PLEDs with luminance ranging from 145 cd.m-2 to 540 cd.m-2. Then, chemical sensors and biosensors have been fabricated by printing polymers and proteins on Surface Acoustic Wave (SAW) devices. The ability of LIFT to transfer several sensing elements on a same device with high resolution allows improving the selectivity of these sensors and biosensors. Gas sensors based on the deposition of semiconducting oxide (SnO2) and biosensors for the detection of herbicides relying on the printing of proteins have also been realized and their performances overcome those of commercial devices. At last, we successfully laser-printed thermoelectric materials and realized microgenerators for energy harvesting applications.
A comparative study of the ejection dynamic of organic materials by Laser-Induced Forward Transfer technique has
been performed using nanosecond and picosecond pulses for applications in plastic micro-electronics. The ejection of
organic materials has been carried out with various thicknesses and with and without a sacrificial metallic release layer
inserted between the substrate and the organic donor film. The advantage of this technique is to preserve organic layers
from being damaged by thermal and photochemical effects during the interaction. The dynamic of the process has been
investigated by shadowgraphic imaging during 1.5 μs after the laser irradiation, under atmospheric conditions. We have
determined the velocity of the transferred material and studied the influence of the metallic layer during the ejection
using a wide range of fluencies. The high directivity of the ejected material offers the possibilities of high spatial
resolution for the manufacture of micro-structures in non contact LIFT technique. The study of the influence of the
distance between the donor and acceptor substrates on the deposit functionality is discussed.
In order to control the technique of laser-induced forward transfer (LIFT) in ultrashort regimes, it is necessary to understand the different basic mechanisms involved during the three steps: ablation-transfer-deposition. Back ablation of Cr thin film has been studied and compared to the front ablation of the same film in the same conditions. Experiments have been performed using ultrashort laser pulses (800 nm, 100 fs). The dynamics of the plumes have been monitored with a gated intensified charge coupled device (ICCD) camera. Image analysis gave us indications on the velocity and the composition of the ejected material. A parametric study of the ablation thresholds and ablation dynamics has been carried out as a function of the incident laser fluence and the thickness of the metal layer. These results contribute to optimize a process of LIFT. Transfers of Cr on glass and Silicon were obtained with a good spatial resolution.
Experiments of laser-induced forward transfer (LIFT) have been performed using ultrashort laser pulses (800nm, 100fs). 40nm of Cr thin film have been transferred on glass and Silicon acceptor substrates in different conditions. The analysis of the deposits was carried out by optical and electronic scanning microscopy. An optimisation of the process has been carried out and a good resolution of the patterns was obtained. The dynamics of the plume has been monitored with a gated ICCD camera and the images analysis gave us indications on the transfer of the material.
We studied the extension of LIFT method to the deposition of Cr thin film in the nanosecond regime. The major objective was to perform high-speed visualisation of the different phenomena involved in LIFT process using a CCD camera.
The Cr thin films (40 nm thickness), previously deposited on glass substrates by a conventional technique, were irradiated by a SPECTRA PHYSICS 2ω Nd:YAG laser (λ=532 nm, τ=7ns, 500mJ/pulse, 10Hz).
The dynamics of the plume was monitored using a CCD camera. Photos were taken at different delay times after laser irradiation. The timing of both the laser pulse and the gate opening of the CCD camera was controlled by a programmable pulse generator. For plasma visualization we have set the gate width at 5 ns.
Standard anodized aluminum samples with about 20 micrometer thick oxide layer were investigated for cleaning study by means of laser pulses. The removal mechanism was studied for short laser pulses at 1064 nm, 532 nm and 248 nm wavelength in air and water. The samples were examined using scanning electron, optical microscopy. Photoacoustic, shock wave measurements and high-speed visualization have been set-up. The experiments were carried out in a new cleaning set-up, which allows a liquid surrounding medium. We investigate the influence of the surrounding medium and the dependence of the laser cleaning efficiency on energy densities and number of pulses. The ablation threshold and ablation mechanisms vary due to the different absorptance of the oxide and aluminum at different wavelength. The surroundings influence has been shown.
In former laser removal experiments of 20 micrometers anodized aluminum layer in air, we found at 1064 nm and 532 nm wavelength a mechanical breaking of the film. In this paper, we present our photoacoustic measurement with a piezoceramic. The experiments were carried out with the aim to investigate the ablation mechanism in dependence on the energy density for 1064 nm and 248 nm laser wavelength. The main result is a strong change of the acoustic signal and shock wave velocity for the first and second laser pulse in amplitude and temporal behavior. To verify this, the experiments are repeated with an ultra fast camera, which allows to record the shock wave in the surrounding air and to visualize the breaking particles of 100 micrometers size. We found a changing of the ablation mechanism with the pulse number.
This paper deals with an experimental study on the mechanisms of laser surface cleaning process in a liquid medium. Experiments have been performed with oxides of different compositions irradiated with two different wavelengths: 1064 nm, 532 nm. Interpretations have been inferred from high speed visualizations, pressure recordings and surface samples analysis. Interesting results on the dynamics of the cavity resulting from ablation and its potential contribution to the cleaning effects have been carried out.
We have characterized laser-induced shock wave in water. Pressure measurements have been carried out using piezoelectric sensors and optical methods (interferometer, high-speed visualization). These experiments give us information on the pressure amplitude, the rise time, the pressure pulse duration, the energy, the shock wave velocity, and the pressure decay. These researches find applications in various fields such as: laser cleaning of sensitive surface, pressure probes calibration, medical treatments (intraocular surgery, lithotripsy).
This paper deals with an experimental and numerical approach of laser induced dielectric breakdown in a liquid. The experimental set-up and especially the high speed visualization device involved, are presented. Results on physical characteristics of the phenomena are obtained with the visualization techniques and compared with numerical investigations.
This paper is concerned with a basic study of vapor bubbles induced by a high power laser beam. It described preliminary studies which should lead to the validation of a laser/ matter interaction code and an hydrodynamic code by optical cavitation experiments. In a first time the experimental arrangements for the generation of a centimeter bubble and for the diagnosis are presented. Visualisations of shock waves and bubbles, pressure and energy mesurements leading to determine a distribution of energy are shown. Then a moderation of the energy depositing and its insertion in a laser/ matter interaction calculation code is presented. A version of the hydrodynamic calculation code PISCES adapted to the study of vapor bubble dynamic and propagation of pressure waves generated during the breakdown and during the collapses is then described (utilization of a multiphase equation of state adapted to the problem).