• Light Scattering

Light scattering by particles is the process by which small particles (macromolecues, micelles, blood cells) scatter light causing optical phenomena such as the blue color of the sky, and halos. We are using a process when incident light of energy is absorbed by a system (polymers, micelles, blood cells) and subsequently light of energy is emitted. Static light scattering measures the average scattered intensity of a population of particles in solution by integrating the scattered signal over a period of time. ... Dynamic light scattering monitors the fluctuations of the scattered photons over very short time intervals from the sample. (Macromolecules, 49(5), 1873-1881, 2016)

• Small Angle X-ray and Neutron Scattering

Small-angle X-ray scattering (SAXS) is an analytical technique that measures the intensities of X-rays scattered by a sample as a function of the scattering angle. ... A SAXS signal is observed whenever a material contains structural features on the length scale of nanometers, typically in the range of 1-100 nm. 

Small-angle neutron scattering (SANS) is an experimental technique that uses elastic neutron scattering at small scattering angles to investigate the structure of various substances at a mesoscopic scale of about 1–100 nm.

Small angle neutron scattering is in many respects very similar to small-angle X-ray scattering (SAXS); both techniques are jointly referred to as small-angle scattering (SAS). Advantages of SANS over SAXS are its sensitivity to light elements, the possibility of isotope labelling, and the strong scattering by magnetic moments. (Macromolecules, 2019, 52, 6502-6513)

• Langmuir Blodgett 

A Langmuir–Blodgett (LB) film is a nanostructured system formed when Langmuir films—or Langmuir monolayers (LM)—are transferred from the liquid-gas interface to solid supports during the vertical passage of the support through the monolayers. LB films can contain one or more monolayers of an organic material, deposited from the surface of a liquid onto a solid by immersing (or emersing) the solid substrate into (or from) the liquid. A monolayer is adsorbed homogeneously with each immersion or emersion step, thus films with very accurate thickness can be formed. This thickness is accurate because the thickness of each monolayer is known and can therefore be added to find the total thickness of a Langmuir–Blodgett film. The monolayers are assembled vertically and are usually composed either of amphiphilic molecules with a hydrophilic head and a hydrophobic tail or nowadays commonly of nanoparticles. (Colloids and Surfaces A: Physicochem. Eng. Aspects 484, 184–189, 2015)

• XRR (X-ray reflectivity)

X-ray reflectivity (XRR) is a surface-sensitive analytical technique used in chemistry, physics, and materials science to characterize surfaces, thin films and multilayers. It is a form of reflectometry based on the use of X-rays and is related to the techniques of neutron reflectometry and ellipsometry. The basic principle of X-ray reflectivity is to reflect a beam of X-rays from a flat surface and to then measure the intensity of X-rays reflected in the specular direction (reflected angle equal to incident angle). If the interface is not perfectly sharp and smooth then the reflected intensity will deviate from that predicted by the law of Fresnel reflectivity. The deviations can then be analyzed to obtain the density profile of the interface normal to the surface. (Langmuir,21(13), 5647, 2005)

• Polymer Hydrogel

A hydrogel is a network of crosslinked polymer chains that are hydrophilic, sometimes found as a colloidal gel in which water is the dispersion medium. A three-dimensional solid results from the hydrophilic polymer chains being held together by cross-links. The crosslinks which bond the polymers of a hydrogel fall under two general categories: physical and chemical. Physical crosslinks consist of hydrogen bonds, hydrophobic interactions, and chain entanglements (among others). (Macromolecules, 2019, 52, 6502-6513)

• Gelation Kinetics

Metal complexation–based gelation imparts load-bearing hydrogels with striking properties like reversibility, self-healing, and mechanical tunability. Using a bio-inspired metal-catechol complex, these properties have been introduced to a variety of polymer hydrogels, except hyaluronic acid, which is widely used in biological applications. In this research, we developed two different hyaluronic acid (HA) hydrogels by regulating the gelation kinetics of Fe3+ and a catechol cross-linker, including Fe3+-induced covalent bonding and coordination bonding. Dual roles of Fe3+ in catechol-modified HA (HA-CA), Fe3+-catechol coordination, and catechol oxidation followed by a coupling reaction, were selectively applied for different gelations. (Macromolecules, 49(19), 7450-7459, 2016)

• Hydrogel Composites

There have been many strategies and efforts to develop nanocomposite gels for wide applications that display desirable strength and properties, such as self-healing. In this study, self-healable laponite-poly(N-isopropylacrylamide) hydrogels were prepared by γ-ray radiation employing stepwise processes that provide gelation without any chemicals for crosslinking and initiation. This method achieved self-healable properties similar to that of  typical gels crosslinked using crosslinkers and initiators. We found that the main factor of the property is the homogeneous distribution of laponite particles, based on comparisons of samples prepared using various synthetic strategies. Regarding the relationship between synthetic methods and their respective properties, the samples were characterized via swelling ratios, rheological properties, cross-sectional images, and nanostructures. (Polymer, 2021, 214, 123365)

• Flow Cytometry

Flow cytometry (FC) is a technique used to detect and measure physical and chemical characteristics of a population of cells or particles. In this process, a sample containing cells or particles is suspended in a fluid and injected into the flow cytometer instrument. The sample is focused to ideally flow one cell at a time through a laser beam, where the light scattered is characteristic to the cells and their components. Cells are often labeled with fluorescent markers so light is absorbed and then emitted in a band of wavelengths. Tens of thousands of cells can be quickly examined and the data gathered are processed by a computer.

• Microfluidics 

Microfluidics refers to the behavior, precise control, and manipulation of fluids that are geometrically constrained to a small scale (typically sub-millimeter) at which surface forces dominate volumetric forces. It is a multidisciplinary field that involves engineering, physics, chemistry, biochemistry, nanotechnology, and biotechnology. It has practical applications in the design of systems that process low volumes of fluids to achieve multiplexing, automation, and high-throughput screening. Microfluidics emerged in the beginning of the 1980s and is used in the development of inkjet printheads, DNA chips, lab-on-a-chip technology, micro-propulsion, and micro-thermal technologies. (Chemistry Letters, 39, 8, 2010)

• Polymer Characterization

Applied to materials research, combinatorial methodologies allow efficient testing of structure–property hypotheses (fundamental characterization) as well as accelerated development of new materials (materials discovery). Recent advances in library preparation and high-throughput screening have extended combinatorial methods to a wide variety of phenomena encountered in polymer processing. NIST first presents techniques for preparing continuous-gradient polymer “libraries” with controlled variations in temperature, composition, thickness, and substrate surface energy. These libraries are then used to characterize fundamental properties such as polymer-blend phase behavior, thin-film dewetting, block-copolymer order–disorder transitions, and cell interactions with surfaces of biocompatible polymers. (Chemistry Letters, 36(10), 1210-1211, 2007)