Rapid fabrication of large-area concave microlens arrays on PDMS by a femtosecond laser.
26 Sep 2013-ACS Applied Materials & Interfaces (American Chemical Society)-Vol. 5, Iss: 19, pp 9382-9385
TL;DR: It is shown that uniform microlenses with different diameters and depths can be controlled by adjusting the power of laser pulses, which greatly enhances the processing efficiency compared to the classical laser direct writing method.
Abstract: A fast and single-step process is developed for the fabrication of low-cost, high-quality, and large-area concave microlens arrays (MLAs) by the high-speed line-scanning of femtosecond laser pulses. Each concave microlens can be generated by a single laser pulse, and over 2.78 million microlenses were fabricated on a 2 × 2 cm2 polydimethylsiloxane (PDMS) sheet within 50 min, which greatly enhances the processing efficiency compared to the classical laser direct writing method. The mechanical pressure induced by the expansion of the laser-induced plasmas as well as a long resolidifing time is the reason for the formation of smooth concave spherical microstructures. We show that uniform microlenses with different diameters and depths can be controlled by adjusting the power of laser pulses. Their high-quality optical performance is also demonstrated in this work.
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TL;DR: In this article, a femtosecond laser was used to realize periodic line-patterned polydimethylsiloxane (PDMS) surfaces by adjusting the period (D) or average distance of adjacent microgrooves.
Abstract: The superhydrophobicity, controllable water adhesion, anisotropic sliding, and anisotropic wetting, which are four typical aspects of the wettability of solid surfaces, have attracted much interest in fundamental research and practical applications. However, how to use a simple and effective method to realize all those properties is still a huge challenge. Here, we present a method to realize periodic line-patterned polydimethylsiloxane (PDMS) surfaces by a femtosecond laser simply and efficiently. By adjusting the period (D) or average distance of adjacent microgrooves, the as-prepared surfaces can exhibit superhydrophobicity, controllable water adhesion, anisotropic sliding, and anisotropic wetting. We believe that these multifunctional surfaces have enormous potential applications in novel microfluidic devices, microdroplet manipulation, liquid microdroplet directional transfer, and lab-on-chips.
165 citations
TL;DR: In this article, a silicon surface with hierarchical micro/nanostructure is fabricated by a femtosecond laser, and the laser-induced surface shows superhydrophilicity in air and superoleophobicity underwater.
Abstract: Femtosecond laser microfabrication has been recently utilized in interface science to modify the liquid wettability of solid surfaces. In this paper, a silicon surface with hierarchical micro/nanostructure is fabricated by a femtosecond laser. Similar to fish scales, the laser-induced surface shows superhydrophilicity in air and superoleophobicity underwater. The oil contact angles can reach up to 159.4 ± 1° and 150.3 ± 2°, respectively, for 1,2-dichloroethane and chloroform droplets in water. In addition, the surface exhibits ultralow oil-adhesion. In the oil–water–solid three-phase system, water can be trapped in the hierarchical rough structure and form a repulsive oil layer according to the extended Cassie's theory. The contact area between the as-prepared surface and oil droplets is significantly reduced, resulting in superoleophobicity and ultralow oil-adhesion in water. In addition, as a potential application, the working principle diagram of preventing blockage ability of underwater superoleophobic pipes is propounded.
149 citations
TL;DR: In this paper, a kind of rough microstructures was formed on polytetrafluoroethylene (PTFE) sheet by femtosecond laser treatment, which showed durable superhydrophobicity and ultralow water adhesion even after storing in various harsh environment for a long time, including strong acid, strong alkali, and high temperature.
140 citations
TL;DR: In this article, a femtosecond laser microfabrication was used to realize super-hydrophobic patterned polydimethylsiloxane (PDMS) surfaces with tunable adhesion by a femto-conditional laser.
Abstract: We present a rapid, facile, and simple method to realize superhydrophobic patterned polydimethylsiloxane (PDMS) surfaces with tunable adhesion by a femtosecond laser. These surfaces are composed of superhydrophobic laser-induced structures and hydrophobic unstructured square array. The femtosecond laser structured domain shows superhydrophobicity with ultralow water adhesion, while the nonstructured flat PDMS shows ordinary hydrophobicity with ultrahigh water adhesion. By adjusting the relative area fraction of laser structured and nonstructured domains, the as-prepared superhydrophobic surfaces show tunable water adhesion that ranges from ultralow to ultrahigh, on which the sliding angle can be controlled from 1° to 90° (a water droplet cannot slide down even when the as-prepared surface is vertical or turned upside down). The tunable adhesive superhydrophobic surfaces achieved by femtosecond laser microfabrication may be potentially used in microfluidic systems to modulate the mobility of liquid droplets.
137 citations
TL;DR: In this paper, a femtosecond laser is used to successfully fabricate a slippery liquid infused porous surface (SLIPS), which is a kind of 3D porous network microstructure can be directly created on polyamide-6 (PA6) substrate by a one-step femto-cond laser direct writing method.
Abstract: In this Communication, femtosecond laser is first used to successfully fabricate a slippery liquid infused porous surface (SLIPS). A kind of 3D porous network microstructure can be directly created on polyamide-6 (PA6) substrate by a one-step femtosecond laser direct writing method. The preparation process of SLIPS mainly includes three steps: femtosecond laser ablation, fluoroalkyl layer modification, and infusion of lubricating liquid. The porous layer and the substrate layer of this as-prepared SLIPS are inherent one material. Such SLIPS has many advantages over the most reported SLIPS fabricated based on “deposition/coating” methods whose porous layers are foreign materials against the substrates. A broad range of liquids including water, hexadecane, lake water, ink, glycerol, coffee, milk, egg white, and egg yolk can easily slide down the 10° tilted SLIPS, revealing that the resultant SLIPS has excellent liquid-repellent ability. Even though the SLIPS suffers from heavily physical damage, the surface can rapidly self-repair without any additional treatment and obtain slippery property again. The developed SLIPS promises to contribute to the achievement of omniphobic materials in self-cleaning, antifouling, biomedical devices, and fuel transport.
128 citations
References
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TL;DR: In this article, the optical breakdown threshold and ablation depth in dielectrics with different band gaps for laser pulse durations ranging from 5 ps to 5 fs at a carrier wavelength of 780 nm.
Abstract: We report measurements of the optical breakdown threshold and ablation depth in dielectrics with different band gaps for laser pulse durations ranging from 5 ps to 5 fs at a carrier wavelength of 780 nm. For t, 100 fs, the dominant channel for free electron generation is found to be either impact or multiphoton ionization (MPI) depending on the size of the band gap. The observed MPI rates are substantially lower than those predicted by the Keldysh theory. We demonstrate that sub-10-fs laser pulses open up the way to reversible nonperturbative nonlinear optics (at intensities greater than 10 14 Wycm 2 slightly below damage threshold) and to nanometer-precision laser ablation (slightly above threshold) in dielectric materials. [S0031-9007(98)05969-9]
805 citations
TL;DR: In this article, the initial modification and ablation of crystalline silicon with single and multiple Ti:sapphire laser pulses of 5 to 400 fs duration was investigated, and the authors found the phenomena amorphization, melting, re-crystallization, nucleated vaporization, and Ablation to occur with increasing laser fluence down to the shortest pulse durations.
Abstract: We investigated the initial modification and ablation of crystalline silicon with single and multiple Ti:sapphire laser pulses of 5 to 400 fs duration. In accordance with earlier established models, we found the phenomena amorphization, melting, re-crystallization, nucleated vaporization, and ablation to occur with increasing laser fluence down to the shortest pulse durations. We noticed new morphological features (bubbles) as well as familiar ones (ripples, columns). A nearly constant ablation threshold fluence on the order of 0.2 J/cm2 for all pulse durations and multiple-pulse irradiation was observed. For a duration of ≈100 fs, significant incubation can be observed, whereas for 5 fs pulses, the ablation threshold does not depend on the pulse number within the experimental error. For micromachining of silicon, a pulse duration of less than 500 fs is not advantageous.
725 citations
TL;DR: An elastomer-based tunable liquid-filled microlens array integrated on top of a microfluidic network is fabricated using soft lithographic techniques and can be used potentially in dynamic imaging systems and adaptive optics.
Abstract: An elastomer-based tunable liquid-filled microlens array integrated on top of a microfluidic network is fabricated using soft lithographic techniques. The simultaneous control of the focal length of all the microlenses composing the elastomeric array is accomplished by pneumatically regulating the pressure of the microfluidic network. A focal length tuning range of hundreds of microns to several millimeters is achieved. Such an array can be used potentially in dynamic imaging systems and adaptive optics.
399 citations
TL;DR: In this paper, the authors describe the physical processes which come into play in laser-solid interaction on the ultrafast time scale open new routes of modifying the structure and the morphology of materials and offer interesting perspectives in laser materials processing.
391 citations
TL;DR: Compared to the conventional femtosecond two-photon fabrication, this work provides an alternative, effective and cheap processing method for the fabrication of micro optic device that requires arbitrary shape with high surface quality and small scale.
Abstract: We report the fabrication of micro lens using an alternative annular scanning mode with continuous variable layer thickness by two-photon polymerization after multi-parameter optimization. Laser scanning mode and scanning pace parameter are optimized to achieve good appearance. As examples of the results, a 2 × 2 micro spherical lens array with diameter of 15 μm and a micro Fresnel lens with diameter of 17 μm are fabricated. Their optical performances are also tested. Compared to the conventional femtosecond two-photon fabrication, this work provides an alternative, effective and cheap processing method for the fabrication of micro optic device that requires arbitrary shape with high surface quality and small scale.
227 citations