In an article published in Nanomaterials, researchers accomplished laser-induced forward transfer (LIFT) of silica nanoparticle films by utilizing an inexpensive nanosecond laser with a central wavelength of 1064 nm.
The fumed silica was mixed with a small quantity of graphene oxide (GO) to increase the light absorption ability of silica. Experiments were performed to gain insights into the function of GO in the laser-induced forward transfer procedure. A basic line width of 221 mm was sufficient for pattern deposition. The scattering could be adjusted from approximately 2.5% to 17.5% by adjusting the laser fluence.
Additionally, the multi-level information delivery capabilities of the patternable transparent displays based on laser-transferred nanosilica (LTNS) films were exhibited. This laser-induced forward transfer-based method promoted rapid, adaptable, and affordable production of scattering-based translucent patterns or screens for transparent displays.
Advancements in Laser Printing Via the Laser-Induced Forward Transfer Process
Laser printing has emerged as an attractive option for non-contact, on-demand, and highly controllable large-scale production of electrical and optical devices.
A focused laser beam can alter the deposit materials or surface features through sintering, laser-induced ablation, carbonization, reduction, polymerization, metallization, etc. One of these processes, called the laser-induced forward transfer, deposits materials onto target samples using a transfer mechanism.
Typically, a laser-induced forward transfer setup consists of the receiver substrate placed close to the donor layer and a thin donor layer already deposited onto the transparent carrier. The donor material is ejected toward the receiver substrate when the donor layer and transparent carrier interface are exposed to a laser pulse.
Therefore, as a non-destructive, single-step, and additive deposition process, the laser-induced forward transfer is compatible with many potential materials. It also lacks the drawbacks like nozzle clogging in inject printing. As a result, the laser-induced forward transfer attracts increased interest in various electrical and optical applications.
The silica nanoparticle can disperse incident light for various uses, including lighting, diffusion optics, solar cells, and displays. Also, the silica nanoparticle is especially useful for scattering-based transparent displays. Here, the transparent screens packed with the silica nanoparticle are frequently used in scattering-based transparent displays to diffuse incident light from projectors.
As a result, a person can simultaneously view the information on the screen and the real-world content concealed behind it. However, inducing laser-induced forward transfer for laser printing scattering and transparent silica nanoparticle films for transparent displays would be more advantageous.
In this study, the authors described laser-induced forward transfer manufacturing of silica nanoparticle films for transparent displays employing a less expensive nanosecond laser with a central wavelength of 1064 nm.
A small quantity of GO was introduced to the silica since it could not absorb enough light. Experiments were performed to gain an understanding of the function of GO in the laser-induced forward transfer process.
Additionally, the deposition of patterns was accomplished and demonstrated. The study also showed that the scattering could be customized by altering the laser fluence. Patternable transparent displays made of LTNS film were also put on exhibit, demonstrating how information could be delivered on several levels.
With the aid of this laser-induced forward transfer-based technology, translucent patterns or screens for transparent displays could be produced quickly, affordably, and flexibly.
A silica/GO ethanol dispersion was spin-coated onto a microscope glass slide to create the donor film for performing the investigations. Specifically, the modified Hummers method produced GO from graphite flakes. The authors conducted the LIFT process in an ambient air environment and at room temperature. With a pulse width of 10 ns and a repetition frequency of 45 kHz, a nanosecond fiber laser with a wavelength of 1064 nm was employed to fabricate samples.
It should be noted that pure fumed silica donor film devoid of GO was incapable of being transferred, even at the maximum laser fluence of 40 J/cm2 that the laser could produce. Thus, the silica dispersion was mixed with a small quantity of GO at a weight ratio of 1: 5 to lower the transfer threshold.
Then, laser transfer was performed with common laser fluence varying from 4 to 24 J/cm2. When GO was present, the transfer process began at a substantially decreased laser fluence of 8 J/cm2, resulting in relatively matt white colors on the glass substrate of the receiver.
At a laser fluence of 16 J/cm2, the average silica nanoparticle film thickness increased to a peak value of around 4 mm, and the value was sustained while the laser fluence was increased. The transferred silica's light scattering was intense and resulted in bright images.
GO generally supported two elements of silica nanoparticle laser transfer. First, GO increased the donor's ability to absorb light at 1064 nm. The absorption was increased from 7.7% to 16.9% by mixing a small quantity of GO into the fumed silica at a weight ratio of 1:5.
As a result, laser transfer was facilitated by a more vital light-matter interaction. Second, local heat and a significant temperature rise were produced by laser irradiation. These thermal changes resulted in the oxidative combustion of GO to volatile gases.
Transparent displays with silica nanoparticle films were dependent on light transmission and scattering. Some laser fluencies were used to measure the optical spectrum of the LTNS films.
For the scattering transparent displays described here, it was necessary to have a high transmission for visibility and a suitable scattering for efficiency reasons. The experiments used a laser fluence value of 16 J/cm2, which considered the trade-off between transmission and scattering.
Significance and Findings of the Study
In this paper, a less expensive nanosecond laser with a central wavelength of 1064 nm was successfully used for the laser-induced forward transfer fabrication of silica nanoparticle films. The fumed silica was treated with a small quantity of GO to initiate the laser transfer at laser fluences greater than 8 J/cm2. Also, the laser-induced forward transfer procedure involved two GO components - gas generation due to laser-induced breakdown and reduction and improving light absorption.
Pattern deposition with a minimum line width of 221 mm was possible using the laser-induced forward transfer technique. By altering the laser fluence, it was possible to control the scattering from approximately 2.5% to 17.5%.
The paper also presented the patternable transparent displays built using LTNS film, demonstrating its capacity to convey information on various levels. This laser-induced forward transfer-based method encouraged the production of scattering-based translucent patterns or screens for transparent displays in a quick, adaptable, and affordable manner.
Li, R. Z., et al. (2022). Laser-Induced Forward Transferred Optical Scattering Nanosilica for Transparent Displays. Nanomaterials, 12(20), 3674. https://www.mdpi.com/2079-4991/12/20/3674