Variable wettability control of a polymer surface by selective ultrasonic imprinting and hydrophobic coating

Lee, Hyun‐Joong; Park, Keun

doi:10.1007/s00396-016-3902-y

Cited by 13 publications

(3 citation statements)

References 51 publications

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“…Recently, ultrasonic imprinting was developed to replicate micro/nanoscale patterns on flat polymer surfaces using ultrasonic vibration energy [11,12,13,14,15,16]. Ultrasonic imprinting has the advantage of localized heating capability, and has been employed for selective micropattern replication [17,18,19] and for the development of composite micropatterns [20].…”

Section: Introductionmentioning

confidence: 99%

Development of Micropatterns on Curved Surfaces Using Two-Step Ultrasonic Forming

Park

2019

Micromachines

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Nanoimprint lithography (NIL) is a micro/nanoscale patterning technology on thermoplastic polymer films, and has been widely used to fabricate functional micro/nanoscale patterns. NIL was also used to develop micro/nanoscale patterns on curved surfaces by employing flexible polymer stamps or micropatterned metal molds with macroscopic curvatures. In this study, two-step ultrasonic forming was used to develop micropatterns on a curved surface out of a flat metal stamp, by connecting ultrasonic imprinting and stretching processes. Ultrasonic imprinting was used to replicate functional micropatterns on a flat polymer film, using a flat ultrasonic horn and micropatterned metal stamps with prism and dot micropatterns. An ultrasonic stretching process was then used to form a curvature on the patterned film using a curved ultrasonic horn and a soft mold insert, to avoid damage to the pre-developed micropatterns. The ultrasonic horn was designed to have three different tip radii, and the resulting forming depth and curvature formation were investigated experimentally. As a result, three different curved surfaces containing two different micropatterns were obtained. The developed curved films containing micropatterns were then evaluated optically, and showed different optical diffusion and illumination characteristics according to the film curvature and micropattern type. These results indicate that the proposed technology can extend the functionality of conventional micropatterned products by imposing appropriate curvatures.

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Section: Introductionmentioning

confidence: 99%

Development of Micropatterns on Curved Surfaces Using Two-Step Ultrasonic Forming

Park

2019

Micromachines

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“…The functional surfaces, i.e., single surface exhibiting multiple hydrophobic or hydrophilic properties at different locations, were developed by Lee and Park [21] just by fabricating micro/nano hierarchical patterns over the polycarbonate substrate through selective ultrasonic-HE. It was observed that patterned and coated surfaces resulted in a maximum reduction of surface energy, thus exhibiting superhydrophobic behavior having a contact angle of 155.6 ± 4.3°.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of superhydrophobic surface by a dimensional change in surface topography of microchannel on polymer substrate through induction-aided hot embossing: parametric investigation and optimization

Deshmukh,

Rana,

Goswami

2023

Surf. Topogr.: Metrol. Prop.

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Hot embossing (HE) is a micro-fabrication technique employed to create micron-scale patterns on the polymer substrate. An in-house induction-assisted hot embossing (IHE) setup was fabricated to complete the embossing in a short duration as compared to traditional hot embossing process. This work alters the polymer surface topography to make it superhydrophobic for self-cleaning. Fiber laser machining was used to produce four-microchannel designs on an Aluminum-6061 plate in which the microchannel width was varied from 600 μm to 150 μm while maintaining a constant adjacent distance of 300 μm. This textured plate is employed as a mold in the IHE setup. IHE process parameters, embossing temperature, pressure, time, and deembossing temperature were varied to emboss the mold designs on a polyethylene terephthalate substrate. Thereafter, the embossed microchannel height, surface roughness, and water contact angle perpendicular to the embossed microchannels (WCA⟂) were calculated. The parametric analysis examined how operational factors affected the output. The experiment was done as per the central composite design (experimental design) part of the design-of-experiments useful in the response surface model. Parametric research demonstrates that embossed microchannel height and width had a maximum effect on WCA⟂. Type-IV microchannels with 150 μm width demonstrated the highest WCA⟂. The WCA⟂ was mostly impacted by embossed microchannel height; hence a regression model was created using type-IV channel height data. Analysis of variance showed that embossing temperature mainly impacts microchannel height. The recently invented Jaya-algorithm optimized this model to increase embossed microchannel height and WCA⟂. Setting the parameters at the best level predicted by Jaya-algorithm yielded an embossed microchannel height inaccuracy of 2.18%. The WCA⟂ measured on the surface of a sample prepared at the best parameters was found to be 154.71°± 2°. Lastly, FTIR (Fourier-transform-infrared-spectroscopy) test showed no chemical composition change between the embossed and bare samples.

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“…It has been shown that the cycle time of hot embossing micro structures from thermoplastic polymers can be shortened to some seconds if the polymer is heated by ultrasonic vibrations instead of heating up the entire tool (Sackmann et al 2015;Lee and Park 2016;Š akalys et al 2016;Mekaru and Yano 2016;Zhu et al 2017;Liu et al 2018). Obviously, the polymer is held longer at an elevated temperature even when it gets into contact to a cold tool.…”

Section: Introductionmentioning

confidence: 99%

Process windows of ultrasonic thermoforming of micro structures

Peng

Schomburg

2020

Microsyst Technol

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Ultrasonic thermoforming of micro structures is similar as usual thermoforming, but the heat required for softening of the polymer is at least partly generated by ultrasonic vibrations. Cycle times as short as a few seconds are achieved by ultrasonic thermoforming and not much more than a commercially available ultrasonic welding machine is required for the process. This paper describes the process window of this fabrication process for polypropylene foils, 200 lm in thickness, as a function of preheating of the tool. Best results have been obtained at room temperature. Since the process is a function of temperature, it is concluded that production should be performed with a tool preheated to 45°C to avoid an influence by a changing room temperature. The overall size of the samples is limited by the size of the available sonotrodes. The experiments described in this paper were performed on an area of 2 9 2 cm 2 , but larger sonotrodes with an area of, e.g., 8 9 12 cm 2 could also be employed. The size of the process window is a function of both the properties of the polymer and the inclination angle of the side walls of the structures on the tools.

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Variable wettability control of a polymer surface by selective ultrasonic imprinting and hydrophobic coating

Cited by 13 publications

References 51 publications

Development of Micropatterns on Curved Surfaces Using Two-Step Ultrasonic Forming

Development of Micropatterns on Curved Surfaces Using Two-Step Ultrasonic Forming

Fabrication of superhydrophobic surface by a dimensional change in surface topography of microchannel on polymer substrate through induction-aided hot embossing: parametric investigation and optimization

Process windows of ultrasonic thermoforming of micro structures

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