Browsing by Author "Rafique, Muzaffar"

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Open Access
Hydrogel integrated optical fiber sensors and their applications a comprehensive review
(Royal Society of Chemistry, 2023-07-13) Sadeque, Sazid Bin; Chowdhury, Hussain Kawsar; Rafique, Muzaffar; Durmuş, Mehmet Atıf; Ahmed, Kawsar; Hasan, Mehdi; Erbaş, Aykut; Sarpkaya, İbrahim; İnci, Fatih; Ordu, Mustafa
Hydrogel-integrated optical fiber sensors have garnered momentous interest due to their optical properties, biocompatibility, and biodegradability. Integrating active materials with hydrogels facilitates hydrogels to be employed as a smart material that responds to external stimuli in biological or chemical media, allowing them to be a potential candidate for sensing applications. Although substantial research efforts have been made on integrating hydrogels with optical fibers, this field has never been reviewed extensively. In this paper, hydrogel-integrated optical fiber sensors are reviewed comprehensively, including the fundamentals of hydrogels, the synthesis process, and the working principle of various sensing methods. The light-guiding and sensing mechanism adopted by hydrogel-integrated optical fibers is discussed. The current progress in their fabrication procedures is categorized and explained. Finally, we have briefly evaluated the applications of hydrogel-integrated optical fiber sensors in various fields spanning from biosensing to environmental sensing.
Open Access
Molecular investigation of polyelectrolyte hydrogel under mechanical deformation
(2023-07) Rafique, Muzaffar
Polyelectrolyte hydrogels are fascinating materials that can produce electromechanical responses when they are electrically or mechanically deformed. However, the accurate molecular origins of such phenomenon are still unknown, even though it is often ascribed to the change in condensation of counterion levels or alteration of ionic conditions in the pervaded volume of the hydrogel. We used all-atom molecular dynamics (MD) simulations to investigate this behavior by utilizing a polyacrylic acid (PAA) hydrogel immersed in an explicit polar solvent as our model system. In the atomistic MD simulation, we investigated the swelling behavior of polyelectrolyte hydrogels, traditionally computed through the equilibrium of chemical potential and pressure between the system and reservoir. However, we discovered that achieving the equilibrium swelling state was non-trivial, as faster relaxation of the simulation box resulted in lower swelling ratios, while slower relaxation led to larger swelling ratios. To address this challenge, we employed theoretical calculations with a Gaussian state as the reference to estimate the hydrogel’s swelling ratio effectively. In our computational study, we investigated the response of PAA polyelectrolyte hydrogel from weak to highly swollen (i.e., between 60 to 90% solvent content) when subjected to uniaxial mechanical compression and extension. Our primary aim is to compute the condensed counterions at different deformations at the microscopic level. We found out that condensation of counterion shows highly non-monotonic behavior when they are mechanically deformed, with an overall increase in total counterion condensation when the PAA hydrogel is uniaxially compressed or stretched. However, this effect diminishes for weakly swollen gel because a large fraction of counterions are already condensed on the polyelectrolyte polymer. Upon closer examination, we found that counterion condensation increases along the stretched chains in the hydrogel. on the one hand, this increase reaches to maximum value for certain deformation ratios after that, we see a decline in the condensation of counterions when the hydrogel chains are stretched further. On the other hand, we see a very minimal increase in condensation when the hydrogel is compressed, and chains are collapsed state. We also analyzed the single polyelectrolyte chains, which also displayed a qualitatively similar response. This observation gives us insight that polymer chain conformations affect the distribution of counterions in the gel. We further investigated the counterion condensation behavior for polyelectrolyte solutions at their critical concentration level. However, we don’t see any deformation-dependent counterion condensation. This suggests the importance of hydrogel topology, which constrains the polyelectrolyte chain ends and leads to the observed behavior. These extensive molecular dynamics simulations shed light on the interesting and heterogeneous behavior of counterion condensation when the hydrogel is deformed, showing a rich electrostatic response behavior. These findings contribute significantly to the understanding of the underlying behavior of mechanically deformed polyelectrolyte hydrogels.
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Services of edith cold during and after Armenian Deportation from Hacin
(Bilkent University, 2018) Haque, Umar Ul; Rafique, Muzaffar; Abazeed, İbrahim Alrshied; Ashok, Vanshdeep; Arshad, Muhammad Nauman
Bu makale, bir misyoner olan Edith Cold’un Mayıs 1915’te ermenilerin Hacin’den sınır dışı edilmelerinden önce, bu vaka esnasında ve bunun sonrasında verdiği hizmetleri ele alıyor. Ele alınan konular arasında Cold tarafından yürütülen amerikan okulu da var. ermenilerin Makale, Aralık 1918’de ermenilerin Osmanlı İmparatorluğu’ndan göç edişinde Rusya’nın; durumun restorasyonunda ise Fransa’nın rolünü de kısaca açıklıyor. Makalenin oluşturulmasında temel kaynak olarak ABCFM arşivlerinde bulunan “Statements by Edith Cold” kullanılmıştır, bunun yanında çeşitli gazete haberleri, kitaplar ve internetten faydalanılmıştır. Araştırma, Cold’un barışa yönelik çabalarının ve göç süresince oluşan zor durumlardaki tarafsız tutumunun önemini vurguluyor