Browsing by Subject "Self-cleaning"

Now showing 1 - 6 of 6

Open Access
Blood repellent superhydrophobic surfaces constructed from nanoparticle-free and biocompatible materials
(Elsevier BV, 2021-09) Çelik, N.; Şahin, F; Ruzi, M.; Yay, M.; Ünal, Ekrem; Önses, Mustafa Serdar
Durable and environment friendly superhydrophobic surfaces are needed for a set of important applications. Biomedical applications, in particular, impose stringent requirements on the biocompatibility of the materials used in the fabrication of superhydrophobic surfaces. In this study, we demonstrate the fabrication of mechanically durable superhydrophobic surfaces via an in-situ structuring strategy starting from natural carnauba wax and biocompatible polydimethylsiloxane (PDMS) materials. The transfer of the structure of the paper to a free-standing PDMS film provided the microscale structure. On top of this structured surface, the wax was spray-coated, initially resulting in a relatively homogeneous film with limited liquid repellence. The key in achieving superhydrophobicity was rubbing the surface for in-situ generation of a finely textured wax coating with a water contact angle of 169° and a sliding angle of 3°. The hierarchically structured surface exhibits mechanical robustness as demonstrated with water impact and linear abrasion tests. We finally demonstrate repellence of the surfaces against a range of blood products including platelet suspension, erythrocyte suspension, fresh plasma, and whole blood.
Open Access
Organically modified silica nanostructures based functional coatings for practical applications
(2015) Tuvshindorj, Urandelger
In the past decades, the fabrication of superhydrophobic surfaces have received considerable attention due to the variety of potential applications ranging from biology to industry. Although significant progress has been made in their fabrication and design, there is still need to solve some problems in real-life use of these coatings, such as low stability against external pressure, lack of long term robustness, challenges in presice control over the degree of wettability and the need for facile fabrication methods. In this context, this thesis seeks simple solutions for mentioned problems based on organically modified silica superhyrophobic coatings. First, we investigate the stability of the Cassie state of wetting in transparent superhydrophobic coatings by comparing a single-layer micro-porous coating with a double-layer micro/nanoporous coating. The stability of the Cassie state in coatings were investigated with droplet compression and evaporation experiments, where external pressures as high as a few thousand Pa are generated at the interface. A droplet on a microporous coating gradually transformed to the Wenzel state with increasing pressure. The resistance of the micro/nano-porous surfaces against Wenzel transition during the experiments were higher than microporous single-layer coating and even higher than leaves of Lotus; prevalent natural superhydrophobic surface. Then, we reported a facile method for the preparation hydrophilic patterns on the superhydrophobic ormosil surfaces. On the defined areas of the superhydrophobic ormosil coatings, wetted micropatterns were produced using Ultraviolet/Ozone (UV/O) treatment which modifies the surface chemistry from hydrophobic to hydrophilic without changing the surface morphology. The degree of wettability of the patterns can be precisely controlled depending on the UV/O exposure duration and extremely wetted spots with water contact angle (WCA) of nearly 0º can be obtained. The ormosil coatings and modified surfaces preserve their wettability for months at room conditions. Furthermore, we demonstrated selective and controlled adsorption of protein and adhesion of bacteria on the superhydrophilic patterns which could be potentially used for biological applications.
Open Access
Robust cassie state of wetting in transparent superhydrophobic coatings
(American Chemical Society, 2014) Tuvshindorj, U.; Yildirim, A.; Ozturk, F. E.; Bayındır, Mehmet
This paper investigates the stability of the Cassie state of wetting in transparent superhydrophobic coatings by comparing a single-layer microporous coating with a double-layer micro/nanoporous coating. Increasing pressure resistance of superhydrophobic coatings is of interest for practical use because high external pressures may be exerted on surfaces during operation. The Cassie state stability against the external pressure of coatings was investigated by squeezing droplets sitting on surfaces with a hydrophobic plate. Droplets on the single-layer coating transformed to the Wenzel state and pinned to the surface after squeezing, whereas droplets on the double-layer micro/nanoporous coating preserved the Cassie state and rolled off the surface easily. In addition, the contact angle and contact-line diameter of water droplets during evaporation from surfaces were in situ investigated to further understand the stability of coatings against Wenzel transition. A droplet on a microporous coating gradually transformed to the Wenzel state and lost its spherical shape as the droplet volume decreased (i.e., the internal pressure of the droplet increased). The contact line of the droplet during evaporation remained almost unchanged. In contrast, a water droplet on a double-layer surface preserved its spherical shape even at the last stages of the evaporation process, where pressure differences as high as a few thousand pascals were generated. For this case, the droplet contact line retracted during evaporation and the droplet recovered the initial water contact angle. The demonstrated method for the preparation of robust transparent superhydrophobic coatings is promising for outdoor applications such as self-cleaning cover glasses for solar cells and nonwetting windows.
Open Access
Robust superhydrophobic fabrics by infusing structured polydimethylsiloxane films
(John Wiley & Sons, Inc., 2021-06-22) Celik, N.; Torun, I.; Ruzi, M.; Mustafa Serdar, Önses
Superhydrophobic coatings have large application potential in self-cleaning textiles. Low durability, high cost of fabrication, and environmental concerns over the usage of chemicals such as fluorocarbons limit the utilization of superhydrophobic coatings. This study reports a convenient and inexpensive approach to fabricate robust and fluorine-free superhydrophobic fabrics based on the transfer of structured polymer films and hydrophobic nanoparticles. In this approach, polydimethylsiloxane (PDMS) is infused between sheets of fabric and paper, followed by curing and removal of the paper. This process results in a fabric infused with PDMS whose structure is a negative replica of the paper surface. Then, hydrophobic nanoparticles are sprayed onto the structured PDMS side of the fabric. The infusion of PDMS and subsequent deposition of the hydrophobic nanoparticles enables strong bonding, as shown by the excellent solvent stability of the superhydrophobic fabric under ultrasonication. The proposed approach is universal in that it can be applied to almost any textiles, which upon coating, exhibited superhydrophobicity with a water contact angle of 172° and a sliding angle of 3°. Furthermore, the superhydrophobic fabric showed robust durability against water spray impact and mechanical bending where it can keep superhydrophobicity for at least 200 cycles of each test.
Open Access
Superhydrophobic and omnidirectional antireflective surfaces from nanostructured ormosil colloids
(American Chemical Society, 2013-02-13) Yildirim, A.; Khudiyev, T.; Daglar, B.; Budunoglu, H.; Okyay, Ali Kemal; Bayındır, Mehmet
A large-area superhydrophobic and omnidirectional antireflective nanostructured organically modified silica coating has been designed and prepared. The coating mimics the self-cleaning property of superhydrophobic lotus leaves and omnidirectional broad band antireflectivity of moth compound eyes, simultaneously. Water contact and sliding angles of the coating are around 160 and 10, respectively. Coating improves the transmittance of the glass substrate around 4%, when coated on a single side of a glass, in visible and near-infrared region at normal incidence angles. At oblique incidence angles (up to 60) improvement in transmission reaches to around 8%. In addition, coatings are mechanically stable against impact of water droplets from considerable heights. We believe that our inexpensive and durable multifunctional coatings are suitable for stepping out of the laboratory to practical outdoor applications.
Open Access
Superhydrophobic coatings for food packaging applications: A review
(Elsevier, 2022-06) Ruzi, M.; Celik, N.; Onses, M. Serdar
Food waste is a serious problem in our modern era, causing economic loss and exacerbating issues like hunger, environmental pollution, and water shortage. Residual food is one main culprit that can be easily eliminated by proper packaging. Advanced packaging techniques with self-cleaning and anti-fouling capabilities are critically important to tackle this issue. In this regard, superhydrophobic coatings are emerging as an innovative approach to address many critical issues in the food industry. Superhydrophobic coatings can prevent fouling and contamination of food packages. An additional capability is the minimization of food waste and improving consumer experience due to the easy sliding of food from the inner side of the package. In this article, we provide an overview of recent studies on the application of superhydrophobic coatings and surfaces for food packaging applications, with a focus on studies aimed at reducing residual food waste via superhydrophobic coatings prepared from edible, nontoxic, and ecofriendly materials.