Fabrication of an Anti-Reflective Microstructure on ZnS by Femtosecond Laser Bessel Beams

As an important mid-infrared to far-infrared optical window, ZnS is extremely important to improve spectral transmission performance, especially in the military field. However, on account of the Fresnel reflection at the interface between the air and the high-strength substrate, surface optical loss occurs in the ZnS optical window. In this study, the concave antireflective sub-wavelength structures (ASS) on ZnS have been experimentally investigated to obtain high transmittance in the far-infrared spectral range from 6 μm to 10 μm. We proposed a simple method to fabricate microhole array ASS by femtosecond Bessel beam, which further increased the depth of the microholes and suppressed the thermal effects effectively, including the crack and recast layer of the microhole. The influence of different Gaussian and Bessel beam parameters on the microhole morphology were explored, and three ASS structures with different periods were prepared by the optimized Bessel parameters. Ultimately, the average transmittance of the sample with the ASS microhole array period of 2.6 μm increased by 4.1% in the 6 μm to 10 μm waveband, and the transmittance was increased by 5.7% at wavelength of 7.2 μm.

3-D aluminum nanostructure with microhole array synthesized by femtosecond laser radiation for enhanced light extinction

This article presents 3-D aluminum micro-nanostructures for enhanced light absorption. Periodic microhole arrays were created by firing a train of femtosecond laser pulses at megahertz pulse frequency onto the surface of an aluminum target at ambient conditions. The laser trains ablated the target surface and created microholes leading to the generation of deposited nanostructures inside and around the microholes. These micro-nanostructures showed enhanced light absorption, which is attributed to surface plasmonics induced by the generation of both nano- and microstructures. These micro-nanostructures may be promising for solar cell applications.

3-D aluminum nanostructure with microhole array synthesized by femtosecond laser radiation for enhanced light extinction

This article presents 3-D aluminum micro-nanostructures for enhanced light absorption. Periodic microhole arrays were created by firing a train of femtosecond laser pulses at megahertz pulse frequency onto the surface of an aluminum target at ambient conditions. The laser trains ablated the target surface and created microholes leading to the generation of deposited nanostructures inside and around the microholes. These micro-nanostructures showed enhanced light absorption, which is attributed to surface plasmonics induced by the generation of both nano- and microstructures. These micro-nanostructures may be promising for solar cell applications.

Self-limiting electrospray deposition on polymer templates

Electrospray deposition (ESD) applies a high voltage to liquids flowing through narrow capillaries to produce monodisperse generations of droplets down to hundreds of nanometers in diameter, each carrying a small amount of the delivered solute. This deposition method has been combined with insulated stencil masks for fabricating micropatterns by spraying solutions containing nanoparticles, polymers, or biomaterials. To optimize the fabrication process for micro-coatings, a self-limiting electrospray deposition (SLED) method has recently been developed. Here, we combine SLED with a pre-existing patterned polymer film to study SLED’s fundamental behavior in a bilayer geometry. SLED has been observed when glassy insulating materials are sprayed onto conductive substrates, where a thickness-limited film forms as charge accumulates and repels the arrival of additional charged droplets. In this study, polystyrene (PS), Parylene C, and SU-8 thin films of varying thickness on silicon are utilized as insulated spraying substrates. Polyvinylpyrrolidone (PVP), a thermoplastic polymer is sprayed below its glass transition temperature (Tg) to investigate the SLED behavior on the pre-deposited insulating films. Furthermore, to examine the effects of in-plane confinement on the spray, a microhole array patterned onto the PS thin film by laser dewetting was sprayed with dyed PVP in the SLED mode. This was then extended to an unmasked electrode array showing that masked SLED and laser dewetting could be used to target microscale regions of conventionally-patterned electronics.

Performance Optimization of Microvalves Based on a Microhole Array for Microfluidic Chips

A microfluidic chip with a microvalve based on a microhole array is proposed in this paper for the POCT of tumor marker proteins. In order to control the biochemical reaction time accurately and obtain a higher testing sensitivity, the parameters of the microhole array are optimized basing on the investigation of the effects of the variation of those parameters on the fluid rate and the residual liquid value in the microvalve region. By conducting liquid flow experiments using microvalves based on microhole arrays with varying microstructural parameters, the residual rate of reaction products is demonstrated to be proportional to the depth and diameter of the microholes and inversely proportional to the distance between the microhole centers. A comprehensive analysis indicates that a microhole depth of 95 μm, a microhole diameter of 230 μm, and a distance between microhole centers of 250 μm not only ensure a sufficiently long delay time, but also reduce the residual rate of reaction products, thereby providing an optimum microvalve performance that maximizes the detection efficiency and accuracy of microfluidic chips.

Self-Limiting Electrospray Deposition on Polymer Templates

<p>Electrospray deposition (ESD) applies a high voltage to liquids flowing through narrow capillaries to produce monodisperse generations of droplets down to hundreds of nanometers in diameter, each carrying a small amount of the delivered solute. This deposition method has been combined with insulated stencil masks for fabricating micropatterns by spraying solutions containing nanoparticles, polymers, or biomaterials. To optimize the fabrication process for micro-coatings, a self-limiting electrospray deposition (SLED) method has recently been developed. Here, we combine SLED with a pre-existing patterned polymer film to study SLED’s fundamental behavior in a bilayer geometry. SLED has been observed when glassy insulating materials are sprayed onto conductive substrates, where a thickness-limited film forms as charge accumulates and repels the arrival of additional charged droplets. In this study, polystyrene (PS), Parylene C, and SU-8 thin films of varying thickness on silicon are utilized as insulated spraying substrates. Polyvinylpyrrolidone (PVP), a thermoplastic polymer is sprayed below its glass transition temperature (T_g) to investigate the SLED behavior on the pre-deposited insulating films. Furthermore, to examine the effects of in-plane confinement on the spray, a microhole array patterned onto the PS thin film by laser dewetting was sprayed with dyed PVP in the SLED mode. This was then extended to an unmasked electrode array showing that masked SLED and laser dewetting could be used to target microscale regions of conventionally patterned electronics.</p>

Self-Limiting Electrospray Deposition on Polymer Templates

<p>Electrospray deposition (ESD) applies a high voltage to liquids flowing through narrow capillaries to produce monodisperse generations of droplets down to hundreds of nanometers in diameter, each carrying a small amount of the delivered solute. This deposition method has been combined with insulated stencil masks for fabricating micropatterns by spraying solutions containing nanoparticles, polymers, or biomaterials. To optimize the fabrication process for micro-coatings, a self-limiting electrospray deposition (SLED) method has recently been developed. Here, we combine SLED with a pre-existing patterned polymer film to study SLED’s fundamental behavior in a bilayer geometry. SLED has been observed when glassy insulating materials are sprayed onto conductive substrates, where a thickness-limited film forms as charge accumulates and repels the arrival of additional charged droplets. In this study, polystyrene (PS), Parylene C, and SU-8 thin films of varying thickness on silicon are utilized as insulated spraying substrates. Polyvinylpyrrolidone (PVP), a thermoplastic polymer is sprayed below its glass transition temperature (T_g) to investigate the SLED behavior on the pre-deposited insulating films. Furthermore, to examine the effects of in-plane confinement on the spray, a microhole array patterned onto the PS thin film by laser dewetting was sprayed with dyed PVP in the SLED mode. This was then extended to an unmasked electrode array showing that masked SLED and laser dewetting could be used to target microscale regions of conventionally patterned electronics.</p>

Engineering Micropatterned Surfaces for Controlling the Evaporation Process of Sessile Droplets

Controlling the evaporation process of a droplet is of the utmost importance for a number of technologies. Also, along with the advances of microfabrication, micropatterned surfaces have emerged as an important technology platform to tune the wettability and other surface properties of various fundamental and applied applications. Among the geometrical parameters of these micropatterns, it is of great interest to investigate whether the arrangement of the patterns would affect the evaporation process of a sessile liquid droplet. To address this question, we fabricated four microhole arrays with different arrangements, quantified by the parameter of “eccentricity”. The results suggested that, compared to smooth substrates, the evaporation mode was not only affected by engineering the microhole arrays, but also by the eccentricity of these micropatterns. The values of contact angle hysteresis (CAH) were used to quantify and test this hypothesis. The CAH could partially explain the different evaporation modes observed on the microhole arrays with zero and non-zero values of eccentricity. That is, on microhole arrays with zero eccentricity, CAH of water droplets was comparatively low (less than 20 ° ). Consistently, during the evaporation, around 60% of the life span of the droplet was in the mixed evaporation mode. Increasing the eccentricity of the microhole arrays increases the values of CAH to above 20 ° . Unlike the increasing trend of CAH, the evaporation modes of sessile droplets on the microhole array with non-zero values of eccentricity were almost similar. Over 75% of the life span of droplets on these surfaces was in constant contact line (CCL) mode. Our findings play a significant role in any technology platform containing micropatterned surfaces, where controlling the evaporation mode is desirable.