https://pubs.rsc.org/en/content/articlepdf/2017/PY/C6PY01585A

Stimuli-responsive polymers and their applications

The area of artificial muscle is a highly interdisciplinary field of research that has evolved rapidly in the last 30 years. Recent advances in nanomaterial fabrication and characterization, specifically carbon nanotubes and nanowires, have had major contributions in the development of artificial muscles. However, what can artificial muscles really do for humans? This question is considered here by first examining nature's solutions to this design problem and then discussing the structure, actuation mechanism, applications, and limitations of recently developed artificial muscles, including highly oriented semicrystalline polymer fibers; nanocomposite actuators; twisted nanofiber yarns; thermally activated shape-memory alloys; ionic-polymer/metal composites; dielectric-elastomer actuators; conducting polymers; stimuli-responsive gels; piezoelectric, electrostrictive, magnetostrictive, and photostrictive actuators; photoexcited actuators; electrostatic actuators; and pneumatic actuators.

Artificial Muscles: Mechanisms, Applications, and Challenges.

Pancě Naumov,*,† Stanislav Chizhik,‡,§ Manas K. Panda,† Naba K. Nath,† and Elena Boldyreva*,‡,§ †New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates ‡Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of Russian Academy of Sciences, ul. Kutateladze, 18, Novosibirsk 630128, Russia Novosibirsk State University, ul. Pirogova, 2, Novosibirsk 630090, Russia

Mechanically Responsive Molecular Crystals

Evaluation of water quality using water quality index (WQI) method and GIS in Aksu River (SW-Turkey)

Methods, Morphologies, and Applications Shuai Chen,†,‡ Paul Slattum, Chuanyi Wang,*,† and Ling Zang* †Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011, China ‡The Graduate School of Chinese Academy of Science, Beijing 100049, China Nano Institute of Utah and Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, United States Vaporsens Inc., Salt Lake City, Utah 84112, United States

Self-Assembly of Perylene Imide Molecules into 1D Nanostructures: Methods, Morphologies, and Applications

Water samples have been collected from a part of Surma River along different points and analyzed for various water quality parameters during dry and monsoon periods Effects of industrial wastes, municipal sewage, and agricultural runoff on river water quality have been investigated The study was conducted within the Chattak to Sunamganj portion of Surma River, which is significant due to the presence of two major industries-a paper mill and a cement factory The other significant feature is the conveyors that travel from India to Chattak This study involves determination of physical, biological and chemical parameters of surface water at different points The river was found to be highly turbid in the monsoon season But BOD and fecal coliform concentration was found higher in the dry season The water was found slightly acidic The mean values of parameters were Conductivity 84–805μs; DO: dry- 552 mg/L, monsoon-572 mg/L; BOD: dry-1 mg/L, monsoon-0878 mg/L; Total Solid: dry-1494 mg/L, monsoon- 1457 mg/L A model study was also conducted and values of different model parameters were estimated

/pdf/water-quality-parameters-along-rivers-5di3bul8g7.pdf

Water quality parameters along rivers

Polymer-based stimuli-responsive polymers and materials have been of considerable interest for many years owing to their ability to convert a chemical or physical stimulus into an observable change in a system. Hydrogel-based thin films, assemblies, and particles (microgels and nanogels) have been designed to respond to a variety of stimuli for a number of potential applications in tissue engineering, artificial muscles, valves, and actuators. Hydrogels are of particular interest owing to their mechanical properties, chemical diversity, and hydration properties, which allow them to interface well with biological systems. Recently, responsive hydrogels and polymer-based thin films have been developed as programmable soft matter or motors by exploiting conformational changes of the polymer that affects the system. 6] Of specific interest to the investigation here are responsive polymer-based systems that are able to do work, that is, lift a mass. These systems, often referred to as artificial muscles, have been the subject of intense research owing to their potential to control movements in mechanical motors. One of the most well studied responsive polymers to date is poly(N-isopropylacrylamide) (pNIPAm), which shows random-coil-to-globule transition at temperatures below 32 8C. 15] Charged pNIPAm-based microgels have been synthesized and used for various applications. By far, the most common chemical functionality added to pNIPAm-based microgels is acrylic acid (AAc). AAc is a weak acid, having a pKa of approximately 4.25, therefore at pH> 4.25 the AAc groups are deprotonated, thus making the microgels negatively charged (polyanionic), while they are neutral at pH< 4.25 owing to AAc protonation. At high pH values the microgels swell because of the charge–charge (Coulombic) repulsion in the polymer network of the microgel. Herein we present a pNIPAm-microgel-based device that is able to do work and lift masses many times the mass of the device, in response to simple changes in the humidity of its environment. The device is constructed by depositing a monolayer of poly(N-isopropylacrylamide)-co-acrylic acid, pNIPAm-co-AAc microgels on an Au-coated substrate. Once deposited, the microgels form a homogenous layer, with the thickness defined by their diameter in solution. The pNIPAm-co-AAc microgels used herein had a solution diameter of (1548 69) nm (measured using differential interference contrast microscopy); the films typically have a thickness of approximately 0.5 of the solution diameter. Subsequently, a solution containing oppositely charged poly(diallyldimethylammonium chloride) (pDADMAC) is added to the microgel-coated substrate and allowed to dry. The pDADMAC solution had a pH of 6.55, which rendered the microgel layer polyanionic. The pDADMAC layer contracts when it dries, owing to water evaporation enhancing hydrophobic interactions between the pDADMAC chains. Since the electrostatic interactions between pDADMAC and the microgels, and the interaction between microgels and the Au layer, are strong, the substrate bends when the polymer dries (Figure 1).

Polymer‐Based Muscle Expansion and Contraction

Responsive polymer-based materials have found numerous applications due to their ease of synthesis and the variety of stimuli that they can be made responsive to. In this review, we highlight the group's efforts utilizing thermoresponsive poly (N-isopropylacrylamide) (pNIPAm) microgel-based optical devices for various sensing and biosensing applications.

/pdf/poly-n-isopropylacrylamide-microgel-based-optical-devices-4qdjqclcx9.pdf

Poly (N-isopropylacrylamide) microgel-based optical devices for sensing and biosensing.

Responsive polymers for analytical applications: a review.

4,4′-Di(acrylamido)-azobenzene was used as a crosslinker in poly(N-isopropylacrylamide)-based microgels. The microgels were subsequently used to fabricate microgel-based optical materials (etalons), which exhibited optical properties that were switchable upon exposure to UV irradiation. We also show that the extent of the response depended on the UV exposure time. These materials could find applications for controlled/triggered drug delivery, as well as in various optical applications.

/pdf/light-switchable-optical-materials-from-azobenzene-9lt7tnw9vr.pdf

Molla R. Islam

Papers

Water quality parameters along rivers

Polymer‐Based Muscle Expansion and Contraction

Poly (N-isopropylacrylamide) microgel-based optical devices for sensing and biosensing.

Responsive polymers for analytical applications: a review.

Light switchable optical materials from azobenzene crosslinked poly(N-isopropylacrylamide)-based microgels