Scaling and mechanism of droplet array formation on a laser-ablated superhydrophobic grid

Farshchian, Bahador,Gatabi, Javad R.,Bernick, Steven M.,Lee, Gwan-Hyoung,Droopad, Ravindranath,Kim, Namwon Elsevier 2018 Colloids and surfaces. A, Physicochemical and engi Vol.547 No.-

<P><B>Abstract</B></P> <P>Superhydrophobic grid patterns were ablated on a hydrophobic polydimethylsiloxane (PDMS) substrate using a nanosecond pulsed laser. The substrate with a wettability contrast (superhydrophobic-hydrophobic) was vertically immersed in a pool of water and withdrawn at different speeds to form droplet arrays spontaneously. The size of droplets was tuned by controlling the withdrawal speed (<I>S</I> <SUB>w</SUB>), which resulted in different contact line speeds on non-irradiated cell (NIC) and laser-irradiated grid (LIG) areas with different surface properties of no-slip and partial-slip conditions, respectively. The ratio of the contact line speeds on NIC and LIG areas (<I>S</I> <SUB>NIC</SUB>/<I>S</I> <SUB>LIG</SUB>) decreased exponentially with the withdrawal speed, leading to formation of larger droplets on NIC. A geometric scaling model predicted the size of droplets formed on NIC arrays over a range of contact line speeds on NIC and LIG, the ratio of the contact line speeds, the withdrawal speed, and the size of NIC.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Laser-induced superhydrophobic grid patterns on PDMS for droplet arrays formation

Farshchian, Bahador,Gatabi, Javad R.,Bernick, Steven M.,Park, Sooyeon,Lee, Gwan-Hyoung,Droopad, Ravindranath,Kim, Namwon Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.396 No.-

<P><B>Abstract</B></P> <P>We demonstrate a facile single step laser treatment process to render a polydimethylsiloxane (PDMS) surface superhydrophobic. By synchronizing a pulsed nanosecond laser source with a motorized stage, superhydrophobic grid patterns were written on the surface of PDMS. Hierarchical micro and nanostructures were formed in the irradiated areas while non-irradiated areas were covered by nanostructures due to deposition of ablated particles. Arrays of droplets form spontaneously on the laser-patterned PDMS with superhydrophobic grid pattern when the PDMS sample is simply immersed in and withdrawn from water due to different wetting properties of the irradiated and non-irradiated areas. The effects of withdrawal speed and pitch size of superhydrophobic grid on the size of formed droplets were investigated experimentally. The droplet size increases initially with increasing the withdrawal speed and then does not change significantly beyond certain points. Moreover, larger droplets are formed by increasing the pitch size of the superhydrophobic grid. The droplet arrays formed on the laser-patterned PDMS with wettability contrast can be used potentially for patterning of particles, chemicals, and bio-molecules and also for cell screening applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Superhydrophobic grid patterns were processed on the surface of PDMS using a pulsed nanosecond laser. </LI> <LI> Droplet arrays form instantly on the laser-patterned PDMS with the superhydrophobic grid pattern when the PDMS sample is simply immersed in and withdrawn from water. </LI> <LI> Droplet size can be controlled by controlling the pitch size of superhydrophobic grid and the withdrawal speed. </LI> </UL> </P>

3D nanomolding and fluid mixing in micromixers with micro-patterned microchannel walls

Farshchian Bahador,Amirsadeghi Alborz,Choi Junseo,Park Daniel S.,Kim Namwon,Park Sunggook 나노기술연구협의회 2017 Nano Convergence Vol.4 No.4

Microfluidic devices where the microchannel walls were decorated with micro and nanostructures were fabricated using 3D nanomolding. Using 3D molded microfluidic devices with microchannel walls decorated with microscale gratings, the fluid mixing behavior was investigated through experiments and numerical simulation. The use of microscale gratings in the micromixer was predicated by the fact that large obstacles in a microchannel enhances the mixing performance. Slanted ratchet gratings on the channel walls resulted in a helical flow along the microchannel, thus increasing the interfacial area between fluids and cutting down the diffusion length. Increasing the number of walls decorated with continuous ratchet gratings intensified the strength of the helical flow, enhancing mixing further. When ratchet gratings on the surface of the top cover plate were aligned in a direction to break the continuity of gratings from the other three walls, a stack of two helical flows was formed one above each other. This work concludes that the 3D nanomolding process can be a cost-effective tool for scaling-up the fabrication of microfluidic mixers with improved mixing efficiencies.

Fabrication of perforated micro/nanopore membranes via a combination of nanoimprint lithography and pressed self-perfection process for size reduction.

Choi, Junseo,Farshchian, Bahador,Kim, Jinsoo,Park, Sunggook American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.6

<P>Artificial membranes with perforated nanopores in defined locations provide an important biomimicking platform for sensing and analysis of biomolecules. This study presents a simple and flexible method to fabricate a freestanding polymer membrane with perforated micro- and nanopores using a combination of nanoimprint lithography (NIL) and pressed self-perfection (PSP) process. NIL was used to define initial pores of a few micrometers in diameter in the SU-8 membrane layer, which was followed by the PSP process where the patterned SU-8 membrane is pressed with a blank silicon wafer at an elevated temperature. This PSP process results in a lateral flow of the SU-8 resist and consequently reduces the pore size in the membrane. With this method, we have demonstrated fabrication of a SU-8 membrane with perforated pores down to approximately 300 nm in diameter. The results indicate that by employing a pore reduction process nanopore membranes can be manufactured without requirements of having a stamp with nanoscale structures and high aspect ratio imprinting with the stamp.</P>

The Role of Oral Contraceptive Pills on Increased Risk of Breast Cancer in Iranian Populations: A Meta-analysis

Ali Soroush,Negin Farshchian,Saeid Komasi,Neda Izadi,Nasrin Amirifard,Afshar Shahmohammadi 대한암예방학회 2016 Journal of cancer prevention Vol.21 No.4

Background: Cancer is one of the main public health issues in the world. Breast cancer is one of the most common types of cancer among women. It is also the second cause of mortality in women. The association between the use of oral contraceptive pills and breast cancer is controversial and a main issue in public health. Some findings have shown that taking these pills does not have a significant effect in increasing the risk of breast cancer, while others have confirmed the carcinogenic effect of these products. These contradictory findings necessitated this meta-analysis, through of all correlated studies in Iran. Methods: All published studies were considered from June 2000 until June 2015, using reliable Latin databases like PubMed, Google Scholar, Google search, Scopus, and Science Direct, and Persian database like SID, Irandoc, IranMedex, and Magiran. Finally, 26 papers were selected: 24 studies were case control while two were population based studies. A total of 26 papers with 46,260 participants were assessed since 2001. Results: Overall estimate of OR for the effect of oral contraceptive pills on breast cancer is 1.521 (CI = 1.25-1.85), which shows that the intervention group had more chance (52%) compared to the control group (P = 0.001). Using these pills increased the risk of breast cancer up to 1.52 times. Conclusions: Because of directly increasing levels of estrogen and the role of estrogen in gaining weight indirectly, oral contraceptive pills can stimulate the occurrence of breast cancer. More studies should be conducted for controlling the period of pill use.

Low cost fabrication of a superhydrophobic V-grooved polymer surface.

Hurst, Steven M,Farshchian, Bahador,Brumfield, Lance,Ok, Jeong Tae,Choi, Junseo,Kim, Jinsoo,Parkl, Sunggook American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.3

<P>Engineering of polymer surfaces to control their wetting properties has shown a wide range of potential applications. In this paper we show low cost fabrication of a superhydrophobic polymer surface via a hierarchical combination of hot embossing, O2 reactive ion etching (RIE) and deposition of a hydrophobic silane. The hot embossing and O2 RIE were used to produce respective micro and nanoscale surface roughness which is a requirement for obtaining superhydrophobic surfaces, while the deposition of a hydrophobic silane modified surface chemistry. In order to increase the water/air interface in the Cassie-Baxter composite wetting model, a brass mold with microscale V-grooves was used for hot embossing. Images of droplets in both static water contact angles and dynamic impact tests with the surface clearly show that the wetting state follows the Cassie-Baxter wetting model. The results of this study indicate that our design of the dual level surface roughness and the fabrication process allow for low cost and easy production of a highly superhydrophobic surface.</P>

Evaluation of KRAS Gene Mutations in Metastatic Colorectal Cancer Patients in Kermanshah Province

Amirifard, Nasrin,Sadeghi, Edris,Farshchian, Negin,Haghparast, Abbas,Choubsaz, Mansour Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.7

Background: Worldwide, colorectal cancer (CRC) is reported to be the fourth most common cancer in men and the third most common in women. KRAS is a proto-oncogene located on the short arm of chromosome 12. The aim of this study was to evaluate the KRAS oncogene and its relationship it with clinicopathologic features in 33 Kurdish patients. Materials and Methods: Metastatic CRC between 2012 and 2016 that came to Imam Reza hospital, Kermanshah province, Iran, were analysed for KRAS mutations using allele specific PCR primers and pyrosequencing. Correlations between variables was analyzed in PASW SPSS and overall survival curves were plotted in Graph Pad prism 5. Results: The mean age for them at diagnosis was $51.5{\pm}12.6$ years (range, 22-76 years). Among the 33 patients that were sequenced, 12 samples in the KRAS gene had a nucleotide change, 11 in codon 12 and 1 in codon 13.There was no significant relationship between the mutation and clinical and pathological aspects of the disease. Conclusions: Knowledge of the KRAS status can help in decision-making to treat metastatic colorectal cancer patients more efficiently and increase survival. However, many Kurdish people due to economic problems are not able to do this valuable genetic test. In addition, we need more careful research of KRAS oncogene at the molecular level in young populations with more patients.

The Evaluation of p53 Polymorphism at Codon 72 and Association With Breast Cancer in Iran: A Systematic Review and Meta-analysis

Abozar Soleimani,Yousef Rahmani,Negin Farshchian,Ali Delpisheh,Kivan Khassi,Afshar Shahmohammadi,Nasrin Amirifard 대한암예방학회 2016 Journal of cancer prevention Vol.21 No.4

Background: Breast cancer is the most common cancer among women in Iran and the world. Multiple environmental factors and genetic variations such as genetic polymorphisms are of its main causes. p53 gene plays an important role in conserving and sustaining the genome as a tumor suppressing gene. Change and polymorphism at codon 72 of p53 gene are correlated with increased risk of lung, mouth, endometrial, prostate, and colorectal cancers, and could be considered an indicator of susceptibility to breast cancer. Methods: Twelve studies (1,190 cases and 1,145 control studies with evaluation of three types of Arg/Arg, Arg/Pro, and Pro/Pro genotypes) have been conducted using keywords, such as polymorphism at codon 72, gene p53 polymorphisms, and the relation between polymorphisms and breast cancer, from databases in Iran, including Magiran, Medlibe, Sid, and Iranmedex, as well as Latin databases such as PubMed, Google Scholar, Science Direct, and Scopus. Results: The OR for Arg/Arg is 1.58 (95% CI: 2.45 to 1.01), the OR for Arg/Pro is 0.75 (95% CI: 1.10 to 0.51), and the OR for Pro/Pro is 0.62 (95% CI: 0.93 to 0.42). p53 gene polymorphism at codon 72 is statistically significant in Arg/Arg and Pro/Pro genotypes. Conclusions: Arg/Arg genotype can be considered as a risk factor for breast cancer, and Pro/Pro genotype can be accounted for as a protective factor against breast cancer.