This paper gives an overview of the most commonly used techniques for nanostructuring and nanochannel fabrication employed in nanofluidics. They are divided into two large categories: top-down and bottom-up methods. Top-down methods are based on patterning on large scale while reducing the lateral dimensions to the nanoscale. Bottom-up methods arrange atoms and molecules in nanostructures. Here, we review the advantages and disadvantages of those methods and give some future perspectives. It is concluded that technology in the region of 1–10 nm is lacking and potentially can be covered by using the pulsed-laser deposition method as a controlled way for thin film deposition (thickness of a few nanometers) and further structuring by the top-down method.

Technologies for nanofluidic systems: top-down vs. bottom-up - a review

We present an overview of the different processes that can result from focusing an ultrafast laser light in the femtosecond–nanosecond time regime on a host of materials, e.g., metals, semiconductors, and insulators. We summarize the physical processes and surface and bulk applications and highlight how femtosecond lasers can be used to process various materials. Throughout this paper, we will show the advantages and disadvantages of using ultrafast lasers compared with lasers that operate in other regimes and demonstrate their potential for the ultrafast processing of materials and structures.

Ultrafast laser processing of materials: a review

Scale-up criteria of laser ablation in the liquid phase with nanosecond pulses is studied for efficient generation of pure ceramic nanoparticles in an aqueous environment. Besides high laser fluence and low height of the applied liquid layer, specific pulse overlap and defined laser repetition rate are required for significant enhancement in nanoparticle productivity. The ablation rate increases by 350% by reducing the liquid film from 8 mm to 2.5 mm owing to reduced absorption and scattering of the incident laser beam by previously ablated nanoparticles. The controlled interpulse distance yields a further increase in material removal rate by another 300% compared to machining in the pulse overlap mode. The residual cavitation bubble from the previous laser pulse and the dispersed nanoparticle interaction with the following laser pulse and optimized temperature gradient in the lattice of the target are assumed to alter productivity. This hypothesis is confirmed by varying the repetition rate with equal la...

Gram Scale Synthesis of Pure Ceramic Nanoparticles by Laser Ablation in Liquid

Laser Beam MicroMachining (LBMM) – A review

Femtosecond versus nanosecond laser machining: comparison of induced stresses and structural changes in silicon wafers

Induced stresses and structural changes in silicon wafers as a result of laser micro-machining

Carbon nanocomposites consist of thermoset or thermoplastic materials filled with carbon nano-particles (nanotubes, bucky balls, etc.). This new and innovative group of materials offers many advantages over standard polymers such as electrical/thermal conductivity and improved structural properties. In the current study, direct diode and Nd:YAG solid-state lasers were used to transmission weld -carbon nanocomposite materials. The experimentation was focused on exploiting the infrared absorbing characteristics of the carbon nanocomposites. Polyetheretherketone (PEEK) based polymer was used in the initial experimentation to quantify weld strength. The experimentation included a complete analysis of the transmission characteristics of the base polymer at 810 nm and 1,064 nm wavelengths, an optical microscope view of the weld cross-section, and transmission welding experimentation. The transmission welding experimentation studied the relationship between average power, travel speed, and weld peel strength. A micro-channel welding experiment was also completed using a polycarbonate (PC) based polymer. The experimentation qualified the minimum feature size that could be joined. The resulsts show that the carbon nanocomposites can be welded in a similar way to carbon black filled materials. The carbon nanocomposites exhibited higher peel strengths at lower average laser power at both 810 and 1064 nm. The carbon nanocomposite material exhibited a unique characteristic of being able to be machined and welded by the same laser wavelength.

Transmission welding of carbon nanocomposites with direct-diode and Nd:YAG solid state lasers

Liquid crystal polymer (LCP) is a new and innovative material being used as an alternative to polyimide in the flexible circuit industry. LCP has many intrinsic benefits over polyimide including lower moisture absorption and improved dimensional stability. However, LCP is very resistant to chemical milling or etching. As a result, other methods for processing the material are being investigated including laser micromachining. In this paper, three frequency converted diode-pumped solid-state (DPSS) Nd:YVO 4 lasers at 355 nm were used to micromachine a LCP film and a copper/LCP laminate. Of them, two are Q-switched lasers operating in the nanosecond regime and the other a mode-locked laser in the picosecond regime. The Q-switched lasers can be operated at pulse repetition rates of 1 to 300 kHz while the mode-locked system is operated at 80 MHz. The micromachining experiments consisted of cutting the 50 μm thick LCP film, cutting the 18 μm thick copper on the film, and drilling micro-vias through both the copper coating and the film substrate. The laser/material interactions and processing speeds were studied and compared. The results show that, compared to polyimide film of the same thickness, LCP film can be more efficiently processed by laser micromachining. In addition, each laser has a unique advantage in processing LCP based flexible circuit materials. The Q-switched lasers are more capable of processing the copper coating while the mode-locked laser can cut LCP film faster with the smallest kerf width.

Micromachining of liquid crystal polymer film with frequency converted diode-pumped Nd:YVO4 laser

Carbon nanocomposites consist of thermoset and thermoplastic materials filled with carbon nano-particles (nanotubes, bucky balls, etc.). This new and innovative group of materials offers many advantages over standard polymers such as electrical/thermal conductivity and improved structural properties. In the current study, Nd:YAG and Nd:YVO 4 solid-state lasers were used to micromachine carbon nanocomposite thermoplastic materials. Experimentation was completed to compare the ability to laser micromachine carbon nanomaterial, carbon black, and unfilled polyurethane. The experimentation studied the relationship between repetition rate, travel speed, and material removal rate. The processing consisted of cutting channels into the innerials using an Nd:YV0 4 laser at 1064, 532, and 355 nm wavelengths. The material removal rate and groove width were quantified for all wavelengths and compared versus the experimental variables. Trials were also completed on laser machining deep channels using an Nd:YAG laser and polyetheretherketone (PEEK) filled with carbon black and carbon nanofiber. The results of the experimentation show similar material removal rates for carbon black and carbon nanofiber filled polyurethane. The PEEK material exhibited high aspect ratio channels with both carbon black and carbon nanofiber fillers. Laser micromachining of polymers which were previously unmachinable using infra-red wavelengths has been demonstrated.

Larry R. Dosser

Papers

Femtosecond versus nanosecond laser machining: comparison of induced stresses and structural changes in silicon wafers

Induced stresses and structural changes in silicon wafers as a result of laser micro-machining

Transmission welding of carbon nanocomposites with direct-diode and Nd:YAG solid state lasers

Micromachining of liquid crystal polymer film with frequency converted diode-pumped Nd:YVO4 laser

Micromachining of carbon nanocomposites with Nd:YAG and Nd:YVO4 frequency-converted solid-state lasers