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2021

174. S. N. Subraveti, S. R. Raghavan

A simple way to synthesize a protective “skin” around any hydrogel.
ACS Applied Materials & Interfaces, 13, 37645 (2021)

173. L. G. Corcoran,…S. R. Raghavan,…A. T. McCormick

Using microemulsion phase behavior as a predictive model for lecithin-Tween 80 marine oil dispersant effectiveness.
Langmuir, 37, 8115 (2021)

172. X. Yue, S. N. Subraveti, G. John, S. R. Raghavan

Phase-selective gelation of the water phase in an oil-water mixture.
Langmuir, 37, 8107 (2021)

171. N. R. Agrawal,…V. John, S. R. Raghavan

Spontaneous formation of stable vesicles and vesicle-gels in polar organic solvents.
Langmuir, 37, 7955 (2021)

170. L. K. Borden, A. Gargava, S. R. Raghavan

Reversible electroadhesion of hydrogels to animal tissues for suture-less repair of cuts or tears.
Nature Communications, 12, 4419 (2021)

169. S. H. Ahn, M. Rath,…S. R. Raghavan

Single-step synthesis of alginate gels with a covalent shell: A simple way to protect encapsulated cells.
ACS Applied Materials & Interfaces, 13, 18432 (2021)

168. B. C. Zarket, H. Wang,…S. R. Raghavan

Multilayer tubes that constrict, dilate, and curl in response to stimuli.
Soft Matter, 17, 4180 (2021)

167. H. Choudhary, M. B. Rudy,…S. R. Raghavan

Foams with enhanced rheology for stopping bleeding.
ACS Applied Materials & Interfaces, 13, 13958 (2021)

166. F. Horkay, J. F. Douglas, S. R. Raghavan

Rheological properties of cartilage glycosaminoglycans and proteoglycans.
Macromolecules, 54, 2316 (2021)

165. M. Fornasier…S. R. Raghavan,…S. Murgia

Surface-modified nanoerythrosomes for potential optical imaging diagnostics.
Journal of Colloid and Interface Science, 582, 246 (2021)

Paper 170

Reversible electroadhesion of hydrogels to animal tissues for suture-less repair of cuts or tears.

We have discovered that cationic gels can be adhered to animal tissues by placing gel and tissue in an electric field (DC, 10 V) for 20 seconds. Applying the DC field with reversed polarity reverses the adhesion. Such electroadhesion can be used to seal cuts or tears in tissues. Our studies suggest that electroadhesion could be potentially used for performing surgery without the need for sutures.

Paper 174

A simple way to synthesize a protective “skin” around any hydrogel.

Fruits and vegetables retain water because they are covered by a hydrophobic skin. In this paper, we devised a way to form a hydrophobic “skin” around hydrogels. The skin is thin, transparent and peelable. For a gel in water, the skin protects it from acids or microbes. For a gel exposed to air, the skin helps resist drying. Skin-covered gels could be used in robotics or other areas.

2020

164. M. Z. Jora, E. Sabadini, S. R. Raghavan

Light-triggered rheological changes in a system of cationic wormlike micelles formulated with a photoacid generator.
Langmuir, 36, 13408 (2020)

163. J. Zhang,..H. Choudhary, S. R. Raghavan,..C. Wang

“Water-in-salt” polymer electrolyte for Li-ion batteries.
Energy & Environmental Science, 9, 8357 (2020)

162. I. C. MacIntire, M. B. Dowling, S. R. Raghavan

How do amphiphilic biopolymers gel blood? An investigation using optical microscopy.
Langmuir, 36, 8357 (2020)

161. B. R. Thompson, B. C. Zarket,…S. R. Raghavan

Liposomes entrapped in biopolymer hydrogels can spontaneously release into the external solution.
Langmuir, 36, 7268 (2020)

160. N. R. Agrawal, X. Yue, S. R. Raghavan

The unusual rheology of wormlike micelles in glycerol: Comparable timescales for chain reptation and segmental relaxation.
Langmuir, 36, 6370 (2020)

Paper 161

Liposomes entrapped in biopolymer hydrogels can spontaneously release into the external solution.

Liposomes are soft nanocontainers used to deliver drugs or cosmetics. They can be entrapped in gels of biopolymers like agar. We found, to our surprise, that entrapped liposomes can escape out of the gel network into water – possibly by squeezing through the pores in the network.

Paper 162

How do amphiphilic biopolymers gel blood? An investigation into the mechanism.

One of our key discoveries is the ability of amphiphilic biopolymers like hmC to convert liquid blood into a gel that retains its weight in an inverted vial. In this paper, we used optical microscopy to probe the underlying mechanism. We found that hmC induces blood cells to cluster, and these clusters connect into a network.

2019

159. J. C. Fernandes, N. R. Agrawal,…S. R. Raghavan

Does the solvent in a dispersant impact the efficiency of crude-oil dispersion?
Langmuir, 35, 16630 (2019)

158. H. Guo,…K. C. DeMella, S. R. Raghavan, Z. H. Nie

Programming the shape transformation of a composite hydrogel sheet via erasable and rewritable nanoparticle patterns.
ACS Applied Materials & Interfaces, 11, 42654 (2019)

157. K. C. DeMella, S. R. Raghavan

Catalyst-loaded capsules that spontaneously inflate and violently eject their core.
Langmuir, 35, 13718 (2019)

156. A. Gargava, S. Ahn,…S. R. Raghavan

Rapid electroformation of biopolymer gels in prescribed shapes and patterns: A simpler alternative to 3-D printing.
ACS Applied Materials & Interfaces, 11, 37103 (2019)

155. N. R. Agrawal, X. Yue,…S. R. Raghavan

Wormlike micelles in polar organic solvents: Extending surfactant self-assembly to new systems and sub-zero temperatures.
Langmuir, 35, 12782 (2019)

154. M. Omarova,…S. R. Raghavan, V. T. John

Biofilm formation by hydrocarbon-degrading marine bacteria and its effects on oil dispersion.
ACS Sustainable Chemistry & Engineering, 7, 14490 (2019)

153. V. S. Balachandran,…S. R. Raghavan,…G. John

Freestanding organogels by molecular Velcro of unsaturated amphiphiles.
Soft Matter, 15, 6263 (2019)

152. J. P. Goertz, K. C. DeMella,…S. R. Raghavan

Responsive capsules that enable hermetic encapsulation of contents and their thermally triggered burst release.
Materials Horizons, 6, 1238 (2019)

151. J. Zheng,…K. DeMella, S. R. Raghavan, C. Wang

High-fluorinated electrolytes for Li-S batteries.
Advanced Energy Materials, 9, 1803774 (2019)

150. M. T. Logun,…S. R. Raghavan,….L. Karumbaiah

Expanding hydrophobically modified chitosan foam for internal surgical hemostasis: Safety evaluation in a murine model.
Journal of Surgical Research, 239, 269 (2019)

149. H. Guo,…K. DeMella, S. R. Raghavan, Z. H. Nie

A shape-shifting composite hydrogel sheet with spatially patterned plasmonic nanoparticles.
Journal of Materials Chemistry B, 7, 1679 (2019)

Paper 155

First example of wormlike micelles in polar solvents like glycerol and formamide.

Self-assembly of surfactants has been well-studied in water, but not in other polar solvents. This paper shows for the first time that one can form long chains (‘wormlike micelles’) by self-assembly in polar solvents like glycerol. The resulting fluids remain viscoelastic at temperatures down to -20°C. They could be useful as anti-icing sprays for aircraft.

Paper 152

Capsules that are leak-proof at room temperature and release contents upon heating.

This paper demonstrates a capsule that can protect its contents with a hermetic seal, i.e., one that is perfectly leak-proof. This is done by making the capsule shell out of a wax with a defined melting temperature. Above this temperature, the shell melts and the contents are released in a burst.

Paper 159

Does the solvent in a dispersant impact the efficiency of crude-oil dispersion?

This paper is part of our ongoing efforts to clear oil spills using food-grade ‘dispersants’. All dispersants contain an organic solvent, but the role of this solvent is usually neglected. It is shown in this paper that the solvent can significantly impact the efficiency with which the oil is dispersed into seawater. Criteria for selecting the optimal solvent are presented.

Paper 156

Electroformation of alginate gels in various shapes and patterns: A simpler alternative to 3D printing.

Making gels by 3D-printing requires special ‘inks’ and an expensive printer. This paper shows a simple way to create gels of the biopolymer alginate. The key is to induce gelation by an electric field, a process called ‘electroformation’. It can be done in any lab at low cost and it yields robust gels in precise shapes and patterns. Cells can be readily embedded in these gels.

Paper 157

Capsules that inflate and explode due to an internal chemical reaction.

The capsule in this paper is designed with catalytic particles in its core. When a fuel is present in the water, a reaction occurs in the capsule, generating oxygen gas. The gas bubbles inflate the capsule until it finally explodes and ejects the core – behavior that is reminiscent of the pufferfish and jellyfish.

2018

148. S. Gharazi, B. C. Zarket,…S. R. Raghavan

Nature-inspired gels with soft and stiff zones that exhibit a 100-fold difference in elastic modulus.
ACS Applied Materials & Interfaces, 10, 34664 (2018)

147. J. Zheng,…S. R. Raghavan,…C. S. Wang

Manipulating electrolyte and solid electrolyte interphase to enable safe and efficient Li-S batteries.
Nano Energy, 50, 431 (2018)

146. O. Owoseni,…S. R. Raghavan,…V. T. John

Microstructural features of surfactant assembly into a gel for application as an oil spill dispersant.
Journal of Colloid and Interface Science, 524, 279 (2018)

145. J. C. Athas, C. P. Nguyen,…S. R. Raghavan

Cation-induced folding of alginate-bearing bilayer gels: Spontaneous folding along the long axis.
Soft Matter, 14, 2735 (2018)

144. S. R. Raghavan, N. J. Fernandes, B. H. Cipriano

Shape-changing tubular hydrogels.
Gels, 4, 18 (2018)

143. S. D. Lacey,…S. R. Raghavan,…L. Hu

Extrusion-based 3D printing of hierarchically porous advanced battery electrodes.
Advanced Materials, 30, 170561 (2018)

142. M. K. Rhoads,…S. R. Raghavan,…W. E. Bentley

Incorporating LsrK AI-2 quorum quenching capability in a functionalized biopolymer capsule.
Biotechnology & Bioengineering, 115, 278 (2018)

Paper 148

Nature-inspired gels with soft and stiff zones that exhibit a 100-fold difference in stiffness.

This paper shows how to create a hydrogel that has many zones, each of which has different mechanical properties. Such multi-zone materials are often found in nature such as the beak of a squid or the spinal discs in our spinal cord. The gel above has four zones, which stretch to different extents. The stiffest zone has a modulus 100 times that of the softest zone.

Paper 145

Cation-induced folding of alginate-bearing gels: Spontaneous folding along the long axis

This paper reports two unusual findings regarding the spontaneous folding of certain gel strips. First, these gels are shown to fold when divalent cations like Ca2+ are added to the water. Second, the rectangular gel folds along its long-axis, as shown above. In contrast, typical gels fold along their short-axis.

2017

141. C. Arya, C. A. Saez, H. Huang, S. R. Raghavan

Clustering of cyclodextrin-functionalized microbeads by an amphiphilic biopolymer.
ACS Applied Materials & Interfaces, 9, 37238 (2017)

140. J. Wang, Y. Feng, N. R. Agrawal, S. R. Raghavan

Wormlike micelles vs water-soluble polymers as rheology-modifiers: Similarities and differences.
Physical Chemistry Chemical Physics, 19, 24458 (2017)

139. A. X. Lu, H. Oh,…W. E. Bentley, S. R. Raghavan

A new design for an artificial cell: Polymer microcapsules with inner compartments that can harbor colloids or microbes.
Chemical Science, 8, 6893 (2017)

138. B. C. Zarket and S. R. Raghavan

Onion-like multilayered polymer capsules synthesized by a bioinspired inside-out technique.
Nature Communications, 8, 193 (2017)

137. Y. Zhang,…S. R. Raghavan, D. Zhang, V. T. John

Amphiphilic polypeptoids transform liposomes into multilamellar structures with close bilayers.
Langmuir, 33, 2780 (2017)

136. A. Chaturvedi,…S. R. Raghavan, M. M. Narayan

Hydrophobically-modified chitosan gauze: A new and effective topical hemostat.
Journal of Surgical Research, 207, 45 (2017)

Paper 139

A new design for an artificial cell: Polymer microcapsules with inner compartments.

This work is inspired by the architecture of eukaryotic cells, which are containers with smaller containers (organelles) in them. In an attempt to mimic this architecture, this paper describes the synthesis of multicompartment capsules (MCCs). The MCCs are made from common biopolymers by a microfluidic approach that uses only water and gas. The number of inner compartments and the contents of each can be tuned; the contents can be particles, enzymes, or bacteria. It is shown that, when two strains of bacteria are placed in separate compartments, a signal from one can trigger a response in the adjacent one.

Paper 138

Onion-like multilayered polymer capsules synthesized by an inside-out technique.

Many materials in nature, including the onion, the egg, and tissues in our body have multiple concentric layers. To mimic this architecture, a simple synthesis technique is shown in this paper that can yield onion-like multilayered polymer capsules. The technique proceeds ‘inside-out’, i.e., each layer grows outward from the previous one. The composition and thickness of each polymer layer can be varied, and by this means, the release of drugs stored in the capsule lumen can be controlled.

This work was highlighted in a variety of news media.

2016

135. C. Arya, H. Oh, S. R. Raghavan

“Killer” microcapsules that can selectively destroy target microparticles in their vicinity.
ACS Applied Materials & Interfaces, 8, 29688 (2016)

134. M. B. Dowling,…S. R. Raghavan,…M. M. Narayan

Determination of efficacy of novel alginate dressing in a lethal arterial injury model in swine.
Injury, 47, 2105 (2016)

133. J. C. Athas, C. P. Nguyen,…S. R. Raghavan

Enzyme-triggered folding of hydrogels: Towards a mimic of the Venus flytrap.
ACS Applied Materials & Interfaces, 8, 19066 (2016)

132. A. Gargava, C. Arya, S. R. Raghavan

Smart hydrogel-based valves inspired by the stomata in plants.
ACS Applied Materials & Interfaces, 8, 18430 (2016)

131. H. Oh, A. X. Lu,…S. R. Raghavan

Light-directed self-assembly of robust alginate gels at precise locations in microfluidic channels.
ACS Applied Materials & Interfaces, 8, 17529 (2016)

130. A. X. Lu,…D. L. DeVoe, S. R. Raghavan

Catalytic propulsion and magnetic steering of microcapsules: Ability to pick-up and drop-off cargo.
ACS Applied Materials & Interfaces, 8, 15676 (2016)

129. R. Ghaffarian,…H. Oh, S. R. Raghavan, S. Muro

Chitosan-alginate microcapsules provide gastric protection and intestinal release of nanocarriers.
Advanced Functional Materials, 26, 3382 (2016) (Cover)

128. Y. C. Kuo,…W. D. D’Souza, S. R. Raghavan

Colloidal properties of nanoerythrosomes derived from bovine red-blood-cells.
Langmuir, 32, 171 (2016)

Paper 135

“Killer” microcapsules that can selectively destroy target microparticles.

One kind of immune cells in our body are the ‘killer’ cells, which target pathogens and deliver a deadly dose of proteins to kill them. In the same vein, this paper puts forward the idea of ‘killer capsules’ that can target another kind of capsule. When the killer is near its target, it delivers a molecule that destroys the target, as shown in the above movie.

Paper 133

Enzyme-triggered folding of hydrogels: Towards a mimic of the Venus flytrap.

This paper describes a hydrogel that folds from a flat sheet to a tube when an enzyme is added to the water at low concentrations. Such self-folding gels are reminiscent of natural structures such as the Venus flytrap, a plant that folds its leaves to entrap its prey (top images). In the bottom images, the self-folding gel is used as the hinge between two rigid gels in a mimic of the Venus flytrap.

Paper 130

Catalytic propulsion and magnetic steering of microcapsules: Pick-up and drop-off of cargo.

This paper is our first foray into the field of robotics. It shows the preparation of ‘micromotors’, which can swim by harvesting a chemical fuel in the water. The path of the motor can be controlled by a magnet. The motor can thus be directed to pick up a cargo, move it to a destination, and finally drop off this cargo.

Paper 132

Smart hydrogel-based valves inspired by the stomata in plants.

Valve-like structures on plant leaves called stomata regulate the flow of water. This paper reports polymer gel-based valves inspired by the stomata. The central pore in the gel opens and allows flow of a liquid only if the liquid satisfies certain properties. For example, in one design, the pore opens to let hot water through, but not cold water. In a second design, water will flow through only if it is both hot and acidic.

2015

127. D. A. Riehm,…S. R. Raghavan, A. V. McCormick

Efficient dispersion of crude oil by food-grade surfactants: Toward greener oil-spill treatments.
Marine Pollution Bulletin, 101, 92 (2015)

126. K. R. Pandit,…S. R. Raghavan, I. M. White

Capture and direct amplification of DNA on chitosan particles in a single PCR-optimal solution.
Analytical Chemistry, 87, 11022 (2015)

125. M. S. Wiederoder,…S. R. Raghavan, D. L. DeVoe

Optical detection enhancement in microfluidic elements using refractive index matching fluids.
Analyst, 140, 5724 (2015)

124. J. S. Arora,…S. R. Raghavan,…V. T. John

Spatially directed vesicle capture in the ordered pores of breath-figure polymer films.
Soft Matter, 11, 5188 (2015)

123. M. B. Dowling, I. C. MacIntire,…S. R. Raghavan

Sprayable foams based on an amphiphilic biopolymer for hemorrhage control without compression.
ACS Biomaterials Science and Engineering , 1, 440 (2015)

122. H. Oh, N. Yaraghi, S. R. Raghavan

Gelation of oil upon contact with water: A bioinspired scheme for the self-repair of oil leaks.
Langmuir, 31, 5259 (2015)

121. G. Peters,…S. R. Raghavan, J. T. Davis

G4-quartet.M+ borate hydrogels.
JACS, 137, 5819 (2015)

120. K. Q. Jiang,…D. L. DeVoe, S. R. Raghavan

Microfluidic generation of uniform water droplets using gas as the continuous phase.
Journal of Colloid and Interface Science, 448, 275 (2015)

119. K. R. Pandit,…S. R. Raghavan, I. M. White

Assessment of surfactants for efficient droplet PCR in mineral oil using the pendant drop technique.
Colloids and Surfaces B, 126, 489 (2015)

118. M. B. Dowling,…S. R. Raghavan, D. R. King

Hydrophobically-modified chitosan foam: Description and hemostatic efficacy.
Journal of Surgical Research, 193, 316 (2015)

Paper 122

Gelation of oil upon contact with water: A scheme for the self-repair of oil leaks.

This paper explores an idea for the self-repair of leaks from a tube. An oily fluid flows through the tube, which is submerged in water. If the tube is damaged, the oil leaks out into the water. At this point, ‘gelator’ molecules in the oil get activated, and they assemble into a fibrous network, thereby sealing the leak. This process is reminiscent of blood clotting, where again blood platelets are activated to aggregate only at the site of a wound.

Paper 123

Sprayable foams based on a biopolymer for hemorrhage control without compression.

This paper extends our work on amphiphilic polymers that can stop severe bleeding and thereby achieve hemostasis. Here, the polymer is used to make a hemostatic foam, which is sprayed onto a bleeding wound in a pig liver. The foam is able to stop the bleeding without any compression being applied. This technology is being commercialized by Gel-e, Inc., a company run by Matt Dowling, who was the first author of this paper.

This work was featured in a variety of scientific media including C&EN.

Paper 120

Microfluidic generation of uniform water droplets using gas as the continuous phase.

Microfluidic techniques are commonly used to form uniform droplets of water. However, this is typically done using water and an immiscible second liquid, i.e., an oil. This paper shows that the oil can be avoided and replaced with air, while still generating uniform aqueous droplets. As demonstrated in the above movie, water droplets at the end of an inner capillary are sheared off by an annular flow of air.

2014

117. R. Zheng,…S. R. Raghavan, N. Pesika, V. T. John

Liposomes tethered to a biopolymer film create a highly effective lubricating surface.
Soft Matter, 10, 9226 (2014)

116. Z. Wei,…J. Athas,…S. R. Raghavan, T. Li, Z. H. Nie

Hybrid hydrogel sheets that undergo pre-programmed shape transformations.
Soft Matter, 10, 8157 (2014)

115. C.-Y. Cheng,…S. R. Raghavan, S.-H. Tung

Mixtures of lecithin and bile salt can form highly viscous wormlike micellar solutions in water.
Langmuir, 30, 10221 (2014)

114. N. A. Burns,…S. R. Raghavan, S. A. Khan

Nanodiamond gels in nonpolar media: Colloidal and rheological properties.
Journal of Rheology, 58, 1599 (2014)

113. J. C. Athas, K. Jun,…V. T. John, S. R. Raghavan

An effective dispersant for oil spills based on food-grade amphiphiles.
Langmuir, 30, 9285 (2014)

112. Y-C. Kuo, C. Hung,…S. R. Raghavan, W. D’Souza

Liposomal nanoprobes that combine anti-EGFR antibodies and MRI contrast agents.
RSC Advances, 2, 33756 (2014)

111. B. H. Cipriano, S. Banik,…R. Briber, S. R. Raghavan

Superabsorbent hydrogels that are robust and highly stretchable.
Macromolecules, 47, 4445 (2014)

110. A. Higham, C. Bonino, S. R. Raghavan, S. A. Khan

Photo-activated ionic gelation of alginate: Real-time monitoring of the crosslinking mechanism.
Soft Matter, 10, 4990 (2014)

109. V. Javvaji, M. B. Dowling,…S. R. Raghavan

Reversible gelation of cells using self-assembling biopolymers: Towards self-assembly of tissue.
Biomaterials Science, 2, 1016 (2014)

108. K. K. Diehn, H. Oh,…R. G. Weiss, S. R. Raghavan

Insights into organogelation from Hansen solubility parameters. Toward a priori predictions of molecular gelation.
Soft Matter, 10, 2632 (2014)

107. Y. Liu,…V. Javvaji,…S. R. Raghavan,…G. F. Payne

Tyrosinase-mediated grafting and crosslinking of phenols confers functional properties to chitosan.
Biochemical Engineering Journal, 89, 21 (2014)

Paper 113

An effective dispersant for oil spills based on food-grade amphiphiles.

Oil spills on the ocean are usually cleared by spraying dispersants, which break up the oil into small droplets. In typical dispersants, some of the components can be toxic. In this paper, an alternative dispersant is designed – one made from food-grade, non-toxic components. The key components are lecithin (a lipid extracted from soy) and Tween 80 (a surfactant used in ice cream), and the two work synergistically to form stable emulsions of crude oil in seawater.

This work was highlighted by a variety of news media, including the UMD Diamondback newspaper.

Paper 111

Superabsorbent hydrogels that are robust and highly stretchable.

Gels that absorb a lot of water, called superabsorbent gels, are used in many products, including diapers. This paper reports a new kind of superabsorbent gel that beats the world record for water-absorption – it can absorb 3000 times its weight in water. The gel is made from commercial monomers using a variation of the typical polymerization strategy. In addition to its superabsorbency, the gel is also notable for its mechanical robustness. In its unswollen state, the gel can be stretched up to 14 times its original length.

This paper was one of the ‘Most Read‘ papers in Macromolecules in 2014.

Citations: > 100 (Google Scholar)

Paper 109

Reversible gelation of cells using self-assembling biopolymers: Towards self-assembly of tissue.

This paper generalizes our results on the effects of amphiphilic polymers on biological cells. Such polymers can embed their hydrophobic side chains in cell membranes. Thereby, the cells get connected into a 3-D network, i.e., into a gel. Gelation in this manner is shown with various cell types, including blood. The end result is a self-assembled network in which the cells form the nodes, much like in a tissue. Gelation can be reversed by adding molecules that capture the hydrophobes.

This work was highlighted by Biomaterials Science.

Paper 108

Insights into molecular gelation from solubility parameters. Toward a priori predictions.

Many ‘gelator’ molecules self-assemble into long fibers, which entangle to produce molecular gels. Such gels form in some organic solvents, but not in others. Can one predict a priori if a gel would arise in a given solvent? This paper puts forward a framework to predict molecular gelation using thermodynamic parameters of the solvents. On a 3-D plot of Hansen solubility parameters, the solvents in which gels are formed cluster into spherical regions, as shown.

The MATLAB program developed for this paper is freely available to the scientific community. If interested, email Prof. Raghavan.

Citations: > 100 (Google Scholar)

2013

106. Y. Chen, V. Javvaji, I. C. MacIntire, S. R. Raghavan

Gelation of vesicles and nanoparticles using water-soluble hydrophobically modified chitosan.
Langmuir, 29, 13624 (2013)

105. H. Oh, V. Javvaji,…D. Danino, S. R. Raghavan

Light-induced transformation of vesicles to micelles and vesicle-gels to sols.
Soft Matter, 9, 11576 (2013)

104. A. X. Lu, K. Q. Jiang, D. L. DeVoe, S. R. Raghavan

Microfluidic assembly of Janus-like dimer capsules.
Langmuir, 29, 13624 (2013)

103. C. Arya,…S. R. Raghavan, S. P. Forry

Capturing rare cells from blood using a packed bed of custom-synthesized chitosan microparticles.
Journal of Materials Chemistry B, 1, 4313 (2013)

102. N. Yan,…S. R. Raghavan, Y. Fang, R. G. Weiss

How do liquid mixtures solubilize insoluble gelators?
JACS, 135, 8989 (2013)

101. M. B. Dowling, A. S. Bagal, S. R. Raghavan

Self-destructing “mothership” capsules for timed release of encapsulated contents.
Langmuir, 29, 7993 (2013)

100. P. Venkataraman,…S. R. Raghavan,…V. T. John

Attachment of a hydrophobically modified biopolymer to oil droplets in the treatment of oil spills.
ACS Applied Materials & Interfaces, 5, 3572 (2013)

99. H. Oh, A. M. Ketner,…D. E. Falvey, S. R. Raghavan

A simple route to ﬂuids with photo-switchable viscosities based on vesicle-micelle transitions.
Soft Matter, 9, 5025 (2013)

98. N. Yan,…K. K. Diehn, S. R. Raghavan,…R. G. Weiss

Pyrenyl-linker-glucono gelators. Correlations of gel properties with gelator structures.
Langmuir, 29, 793 (2013)

97. V. R. Basrur, J. Guo, C. S. Wang, S. R. Raghavan

Synergistic gelation of nanoparticles and molecules to yield conductive free-standing gel electrolytes.
ACS Applied Materials & Interfaces, 5, 262 (2013)

96. H. Shi, W. Ge, H. Oh,…S. R. Raghavan, J. L. Zakin

Photoreversible micellar solutions as smart drag-reducing fluids for district heating/cooling systems.
Langmuir, 29, 102 (2013)

95. H-Y. Lee, K. Hashizaki, K. Diehn, S. R. Raghavan

Reverse self-assembly of lipid onions induced by gadolinium and calcium ions.
Soft Matter, 9, 200 (2013)

94. A. Gupta,…S. R. Raghavan, W. E. Bentley

Encapsulated protein confers “sense and respond” activity to capsules to control quorum sensing.
Biotechnology & Bioengineering, 110, 552 (2013)

Paper 105

Light-induced transformation of vesicles to micelles and vesicle-gels to sols.

Vesicles are nanoscale (~ 100 nm) containers that find application in drug delivery. This paper describes a simple way, using cheap, widely available molecules, to create vesicles that are responsive to light. When exposed to UV light, the vesicles are transformed into much smaller (~ 5 nm) spherical micelles.

Paper 101

Self-destructing “mothership” capsules for timed release of encapsulated contents.

This paper puts forward the idea of capsules that self-destruct after a set time. The capsules have enzymes in their lumen, which slowly degrade the capsule shell. As the microscale structures (termed ‘motherships’) degrade, they release their internal cargo of nanoscale vesicles (termed ‘babyships’). The time it takes for the capsule to degrade can be tuned by the internal enzyme concentration.

Paper 99

A simple route to ﬂuids with photo-switchable viscosities.

This paper represents the culmination of our work on fluids with light-tunable flow properties. It reports a simple, surfactant-based fluid whose viscosity can be reversibly switched a million-fold by two kinds of light. UV light increases the viscosity while visible light decreases it back to its initial value.

Paper 97

Synergistic gelation of nanoparticles and a gelator to yield free-standing gel electrolytes.

Lithium-ion batteries currently use liquid electrolytes for their high conductivity, but the liquids can leak out of the battery. This paper reports electrolytes with liquid-like conductivities but solid-like mechanical properties. This combination of properties is achieved by gelling a Li⁺ salt solution using a molecular gelator coupled with silica nanoparticles. The gel is strong enough that it can be held in one’s hand.

2012

93. K. Jiang,…S. R. Raghavan, D. L. DeVoe

Microfluidic synthesis of macroporous polymer immunobeads.
Polymer, 53, 5469 (2012)

92. J. H. Lee,…S. R. Raghavan, R. Blumenthal

Biopolymer-connected liposome networks as injectable materials capable of sustained drug delivery.
Biomacromolecules, 13, 3388 (2012)

91. Y. Liu, V. Javvaji, S. R. Raghavan,…G. F. Payne

Glucose-oxidase mediated gelation: A simple test to detect glucose in food products.
J. Agricultural & Food Chemistry, 60, 8963 (2012)

90. O. A. Ogunsola,…R. L. Bronaugh, S. R. Raghavan

Structural analysis of “flexible” liposomes: New insights into their skin-penetrating ability.
Soft Matter, 8, 10226 (2012)

89. H-Y. Lee, H. Oh, J. H. Lee, S. R. Raghavan

Shedding light on helical tubules: Real-time observations of tubule self-assembly.
JACS, 134, 14375 (2012)

88. S. J. Banik,…P. Thomas, S. R. Raghavan

A new approach for creating polymer hydrogels with regions of distinct properties.
Macromolecules, 45, 5712 (2012)

87. S. R. Raghavan and J. F. Douglas

The conundrum of gel formation by nanofibers, micelles, and proteins: Gelation without cross-links?
Soft Matter, 8, 8539 (2012)

86. P. Sahoo,…S. R. Raghavan, P. Dastidar

Gel sculpture: Moldable, load-bearing and self-healing supramolecular gel.
Chemistry: A European Journal, 18, 8057 (2012) (Cover)

85. Y. Liu,…S. R. Raghavan, W. Bentley, G. F. Payne

Biofabricating multi-functional soft matter with enzymes and stimuli-responsive materials.
Advanced Functional Materials, 22, 3004 (2012)

84. G. DeCastro,…S. R. Raghavan,..G. Bochicchio

Efficacy of novel modified chitosan sponge dressing in a lethal arterial injury model in swine.
Journal of Trauma, 72, 899 (2012)

83. K. Sun, H. Oh, J. F. Emerson, S. R. Raghavan

A new method for centrifugal separation of blood components using a UV-curable gel.
Journal of Materials Chemistry, 22, 2378 (2012) (Cover)

82. K. Jiang, P. Thomas,…D. DeVoe, S. R. Raghavan

Microfluidic synthesis of monodisperse PDMS microbeads as discrete oxygen sensors.
Soft Matter, 8, 923 (2012)

Paper 88

A new approach for creating polymer hydrogels with regions of distinct properties.

This paper shows a simple, new method to synthesize ‘hybrid gels’ where different zones of the gel have distinct properties. For example, one zone is ‘written’ in a pattern (‘UMD’) within the other. Initially, the hybrid gel appears homogeneous and the pattern is hidden. Subsequently, the pattern can be revealed either optically or thermally.

This work was featured by New Scientist magazine.

Paper 89

Real-time observations of helical tubule assembly by optical microscopy.

This paper reports two interesting discoveries. First, a mixture of a diacetylenic surfactant and an alcohol is shown to form a gel of close-packed vesicles. Next, when this gel is diluted, the vesicles transform first into helical ribbons and then into closed tubules. The transition of ribbons to tubules is visualized in real-time using optical microscopy.

Paper 90

New insights into the skin-penetrating ability of 'flexible' liposomes.

Nanoscale structures that can penetrate through skin have been highly sought after. In this regard, there are many reports on ‘flexible’ liposomes, which are believed to be able to squeeze through pores in the Stratum Corneum, i.e., the outermost layer of skin. This paper examines the structure of a typical formulation of ‘flexible’ liposomes and finds that the liposomes are not really flexible. Instead, the samples are in fact mixtures of liposomes and micelles. Penetration through skin is indeed achieved, and an alternative hypothesis is advanced in the paper as to why this occurs.

Paper 87

The conundrum of gel formation by nanofibers, micelles, proteins: Gelation without cross-links?

Self-assembly into chains is ubiquitous in nature: e.g., wormlike micelles of surfactants, protein filaments such as F-actin, and fibers of molecular gelators. The chains are not cross-linked; yet, all these systems behave as elastic gels. Why? This paper suggests that gelation can occur simply by physical entanglements if the chains are long and stiff.

Times Cited: > 100 (Google Scholar)

Paper 82

Microfluidic synthesis of monodisperse PDMS microbeads as discrete oxygen sensors.

Polydimethylsiloxane (PDMS or silicone) is an inert, nontoxic elastomer. This paper uses a microfluidic approach to create uniform microbeads of PDMS. Moreover, an oxygen-sensitive phosphorescent dye is embedded in these beads during synthesis. The resulting beads can then be used to sense the local oxygen concentration in a sample.

Paper 83

A new method for centrifugal separation of blood components using a UV-curable gel.

Blood is separated from serum by centrifugation in tubes that contain a thixotropic gel. This gel forms a weak barrier between the phases based on density differences. A new concept is described in this paper, which is to make the gel UV-curable. The gel can then be solidified by UV light, thus creating a strong, ‘perfect’ barrier between blood and serum. This technology has been licensed by a startup company, BioSpecimen Technologies, that is being run by our collaborator, Dr. Jane Emerson from USC.

This work was selected for the Back Cover of the issue by J. Mater. Chem. and was highlighted in a variety of news media, including Chemistry World.

2011

81. P. C. Thomas, S. R. Raghavan, S. P. Forry

Regulating oxygen levels in a microfluidic device.
Analytical Chemistry, 83, 8821 (2011)

80. V. Javvaji, A. Baradwaj, G. Payne, S. R. Raghavan

Light-activated ionic gelation of common biopolymers.
Langmuir, 27, 12591 (2011) (Cover)

79. P. C. Thomas, B. H. Cipriano, S. R. Raghavan

Nanoparticle-crosslinked hydrogels as a class of efficient materials for separation and ion exchange.
Soft Matter, 7, 8192 (2011)

78. H. Y. Lee, K. K. Diehn,…S. R. Raghavan

Reversible photorheological fluids based on spiropyran-doped reverse micelles.
JACS, 133, 8461 (2011)

77. K. Q. Jiang, C. Xue,…D. L. DeVoe, S. R. Raghavan

A new approach to micro-manufacturing: Microfluidic magnetic/fluorescent chains.
Small, 7, 2470 (2011) (Frontispiece)

76. H. Shi,…S. R. Raghavan, J. L. Zakin

Light-responsive wormlike micelles as drag reducing fluids with enhanced heat-transfer capabilities.
Langmuir, 27, 5806 (2011)

75. J. E. St.Dennis,…S. R. Raghavan, V. T. John

Carbon microspheres as network nodes in a novel biocompatible gel.
Soft Matter, 7, 4170 (2011)

74. M. B. Dowling, R. Kumar,…S. R. Raghavan

A self-assembling hydrophobically modified chitosan capable of reversible hemostatic action.
Biomaterials, 32, 3351 (2011)

73. L. Ziserman,…S. R. Raghavan,…D. Danino

Unraveling the mechanism of nanotube formation by chiral self-assembly of amphiphiles.
JACS, 133, 2511 (2011) (Cover)

72. H. Y. Lee, K. R. Tiwari, S. R. Raghavan

Biopolymer capsules with polydiacetylenic vesicles as colorimetric sensors of pH and temperature.
Soft Matter, 7, 3273 (2011)

71. M. B. Dowling, V. Javvaji,…S. R. Raghavan

Vesicle capture on patterned surfaces coated with amphiphilic biopolymers.
Soft Matter, 7, 1219 (2011)

70. P. Sahoo, D. Kumar, S. R. Raghavan, P. Dastidar

Supramolecular synthons in designing low molecular mass gelling agents.
Chemistry: An Asian Journal, 6, 1038 (2011) (Cover)

Paper 80

Light-activated ionic gelation of biopolymers including alginate and pectin.

This paper shows how a biopolymer such as alginate can be gelled using light. This is done without any chemical modification to the polymer backbone. The idea is to mix the polymer with certain photoactive molecules and CaCO3 particles. Under UV light, Ca2+ ions are generated, which gel the polymer. Gels can be formed in precise patterns using a photomask.

This paper was selected for the cover of Langmuir.

Paper 79

Nanoparticle-crosslinked hydrogels for efficient separation and ion exchange.

This paper shows the application of a hydrogel containing laponite nanoparticles in separations. The particles have a strong affinity for cationic solutes. Thus, the gel selectively removes a cationic dye from a mixture of cationic and anionic dyes (see above).

Paper 78

Reversible photorheological fluids based on spiropyran-doped reverse micelles.

This paper describes a simple fluid whose viscosity could be reversibly altered by shining light at different wavelengths. The initial yellow fluid contains commercially-available lipids and photosensitive molecules dissolved in cyclohexane. The molecules self-assemble into long chains, and thus the fluid has a high viscosity. Upon irradiation with UV light, the molecules re-assemble into shorter chains, and hence the red fluid has a lower viscosity. Next, upon irradiation with visible light, the original yellow fluid with a high viscosity is recovered.

Citations: > 100 (Google Scholar)

Paper 77

Micro-manufacturing of magnetic and fluorescent chains using a microfluidic device.

Micro-manufacturing implies the use of a microfluidic chip as a miniature factory. Towards this end, this paper uses a chip that takes in a polymer (chitosan) solution as feed, creates polymer droplets, converts them into particles, and then connects those on-chip into functional microchains. Magnetic and/or fluorescent chains can thus be created.

This paper was selected as a Frontispiece by Small.

Paper 72

Biopolymer capsules with polydiacetylenic vesicles as colorimetric sensors of pH and temperature.

This paper demonstrates capsules that non-invasively sense solution pH and temperature. The capsules contain polymerized vesicles of a diacetylene-based amphiphile. Due to the vesicles, the capsules show a blue or red color under different conditions.

Paper 74

A self-assembling biopolymer capable of reversible hemostatic action.

This paper shows that an amphiphilic polymer is able to convert liquid blood into a gel (see above) by a self-assembly mechanism. The same polymer acts as a ‘hemostatic‘ agent, i.e., it rapidly stops bleeding from severe injuries in animal models. This technology won the Invention of the Year award at UMD in 2009. It is being commercialized by Gel-e, Inc., a company run by Matt Dowling, who was the first author of this paper.

This work was highlighted in a variety of scientific media including C&EN.

Citations: > 150 (Google Scholar)

2010

69. J. B. Borak, H-Y. Lee, S. R. Raghavan, D. E. Falvey

Application of PET deprotection for orthogonal photocontrol of aqueous solution viscosity.
Chemical Communications, 46, 8983 (2010)

68. H-Y. Lee,…S-H. Tung, S. R. Raghavan

Can simple salts influence self-assembly in oil? Multivalent cations as gelators of lecithin organosols.
Langmuir, 26, 13831 (2010)

67. S. R. Jadhav,…S. R. Raghavan, G. John

Sugar derived phase-selective molecular gelators as model solidifiers for oil spills.
Angewandte Chemie Int. Edition, 49, 7695 (2010) (Cover)

66. C. Ropp,…S. R. Raghavan, E. Waks, B. Shapiro

Manipulating quantum dots to nanometer precision by control of flow.
Nano Letters, 10, 2525 (2010)

65. J. S. Hong,…S. R. Raghavan, M. Gaitan

Microfluidic directed self-assembly of liposome-hydrogel hybrid nanoparticles.
Langmuir, 26, 11581 (2010)

64. K. Sun and S. R. Raghavan

Thermogelling fluids containing low concentrations of Pluronic F127 and laponite nanoparticles.
Langmuir, 26, 8015 (2010)

63. R. Kumar, A. M. Ketner, S. R. Raghavan

Non-aqueous photorheological fluids based on light-responsive reverse wormlike micelles.
Langmuir, 26, 5405 (2010)

62. R. Kumar and S. R. Raghavan

Thermo-thickening in solutions of telechelic associating polymers and cyclodextrins.
Langmuir, 26, 56 (2010)

Paper 68

Can simple salts influence self-assembly in oil? Multivalent cations as gelators of lecithin sols.

Can salts be dissolved in oil? Indeed they can, as shown by this paper, provided a lipid is also present. Moreover, the type of cation has a key influence on the self-assembly of the lipid. While Na⁺ has no effect, divalent cations like Ca²⁺ and trivalent cations like La³⁺ induce the lipid to form long chains. These chains entangle to produce an organogel.

Paper 64

Thermogelling fluids containing low concentrations of Pluronic F127 and laponite nanoparticles.

This paper shows that a mixture of clay nanoparticles and a polymeric surfactant show thermogelling, i.e., a transition from liquid to gel upon heating to 75°C. The effect is synergistic, i.e., it is exhibited by the mixture, but not the individual components. The hypothesis advanced in the paper for the thermogelling is that it is induced by ‘depletion interactions‘, which arise between the nanoparticles when the surfactant forms micelles at high temperatures.

Paper 63

Non-aqueous photorheological fluids based on light-responsive reverse wormlike micelles.

This paper reports a simple recipe for an oil-based fluid whose viscosity could be tuned by shining light. The fluid contains lipid molecules that self-assemble into long cylindrical chains initially. Irradiation with UV light alters the geometry of the lipids, which makes them re-assemble into short cylinders, causing a 1000-fold drop in viscosity.

2009

61. P. C. Thomas,…S. R. Raghavan, S. P. Forry

A non-invasive thin-film sensor for monitoring oxygen tension during in vitro cell culture.
Analytical Chemistry, 81, 9239 (2009)

60. L. Ziserman,…S. R. Raghavan, D. Danino

Origins of the viscosity peak in wormlike micellar solutions based on catanionics: A cryo-TEM study.
Langmuir, 25, 10483 (2009)

59. W-C. Lai,…S-H. Tung,…S. R. Raghavan

Nanostructured polymers using a self-assembled nanofibrillar scaffold as a reverse template.
Journal of Physical Chemistry B, 113, 8026 (2009)

58. K. Sun, R. Kumar, D. E. Falvey, S. R. Raghavan

Photogelling colloidal dispersions based on light-activated assembly of nanoparticles.
JACS, 131, 7135 (2009)

57. P. Sahoo,…S. R. Raghavan,…P. Dastidar

A combinatorial library of primaryalkylammonium dicarboxylate gelators: A synthon approach.
Langmuir, 25, 8742 (2009)

56. M. B. Dowling, J. H. Lee, S. R. Raghavan

pH-responsive Jello: Gelatin gels containing fatty acid vesicles.
Langmuir, 25, 8519 (2009)

55. B. H. Cipriano, T. Kashiwagi,…S. R. Raghavan

A simple method to improve the clarity and rheological properties of polymer/clay nanocomposites.
ACS Applied Materials & Interfaces, 1, 130 (2009)

54. J. H. Lee, D. Danino, S. R. Raghavan

Polymerizable vesicles based on a single-tailed fatty acid: A simple route to robust nano-containers.
Langmuir, 25, 1566 (2009)

53. B. D. Frounfelker,…D. Danino, S. R. Raghavan

Persistence of birefringence in sheared solutions of wormlike micelles.
Langmuir, 25, 167 (2009)

52. R. Kumar and S. R. Raghavan

Photogelling fluids based on light-activated growth of zwitterionic wormlike micelles.
Soft Matter, 5, 797 (2009)

Paper 58

Photogelling colloidal dispersions based on light-activated assembly of nanoparticles.

This paper shows how to endow a suspension of clay nanoparticles with photoresponsive properties. The low-viscosity suspension (sol) contains a photoacid generator (PAG). The particles are discrete and stabilized. When irradiated with UV light, the PAG generates acid, and the lowering of pH induces the clay particles to assemble into a gel network.

Paper 56

pH-responsive Jello: Gelatin gels containing fatty acid vesicles.

Vesicles (size ~ 100 nm) of oleic acid are embedded in gelatin gels (Jello). The gel has a bluish color due to light scattering from the vesicles. When the gel is contacted above it in the vial with water at pH > 10, the vesicles are transformed into smaller micelles (size ~ 5 nm). The micellar zone is colorless and its interface with the bluish vesicle zone can be seen.

2008

51. B. H. Cipriano,…H. A. Bruck, S. R. Raghavan

Conductivity enhancement of carbon nanotube and nanofiber-based nanocomposites by annealing.
Polymer, 49, 4846 (2008)

50. T. Kashiwagi,…B. H. Cipriano, S. R. Raghavan,…

Relation between the viscoelastic and flammability properties of polymer nanocomposites.
Polymer, 49, 4358 (2008)

49. S. Talwar, L. Scanu, S. R. Raghavan, S. A. Khan

Influence of binary surfactant mixtures on the rheology of associative polymer solutions.
Langmuir, 24, 7797 (2008)

48. S-H. Tung and S. R. Raghavan

Strain-stiffening response in transient networks formed by reverse wormlike micelles.
Langmuir, 24, 8405 (2008)

47. S.-H. Tung, H.-Y. Lee, S. R. Raghavan

A facile route for creating reverse vesicles: Insights into reverse self-assembly in organic liquids.
JACS, 130, 8813 (2008)

46. S-H. Tung, Y-E. Huang, S. R. Raghavan

Self-assembled organogels obtained by adding minute conc. of a bile salt to AOT reverse micelles.
Soft Matter, 4, 1086 (2008)

45. J. Hong,…L. Locascio, M. Gaitan, S. R. Raghavan

Liposome-templated supramolecular assembly of responsive alginate nanogels.
Langmuir, 24, 4092 (2008)

Paper 51

Conductivity enhancement of carbon nanotube and nanofiber-based nanocomposites by annealing.

Carbon nanotubes (CNTs) and nanofibers (CNFs) impart electrical conductivity to polymers. However, the conductivities of extruded polymer/CNT and polymer/CNF composites can be very low initially. This paper shows that annealing the composites can restore the conductivity due to the re-formation of connections between the particles.

Citations: > 150 (Google Scholar)

Paper 47

A facile route for creating reverse vesicles in organic liquids.

Self-assembly of vesicles (nanoscale containers) in water is well-known. But their counterparts in oil (i.e., nonpolar organic liquids) are very rare. This paper demonstrates a new way to form ‘reverse vesicles’ in oil. The approach is very simple and involves the self-assembly of two lipids, one with two long (C18) tails and the other with two short (C4) tails.

Citations: > 80 (Google Scholar)

2007

44. A. K. Kota,…S. R. Raghavan, H. A. Bruck

Quantitative characterization of an interpenetrating phase composite in PS via MWNT percolation.
Nanotechnology, 18, 505705 (2007)

43. R. Kumar,…D. Danino, S. R. Raghavan

Wormlike micelles of a C22-tailed zwitterionic surfactant: From viscoelastic solutions to elastic gels.
Langmuir, 23, 12849 (2007)

42. B. H. Cipriano, T. Kashiwagi, S. R. Raghavan,…

Effects of aspect ratio of MWNTs on flammability properties of polymer nanocomposites.
Polymer, 48, 6086 (2007)

41. A. K. Kota, B. Cipriano,…S. R. Raghavan, H. Bruck

Electrical and rheological percolation in polystyrene/MWCNT composites.
Macromolecules, 40, 7400 (2007)

40. E. J. Danoff,…S. R. Raghavan, D. S. English

Surfactant vesicles for high-efficiency capture and separation of charged organic solutes.
Langmuir, 23, 8965 (2007)

39. A. M. Ketner, R. Kumar,…S. R. Raghavan

A simple class of photorheological fluids: Surfactant solutions with viscosity tunable by light.
JACS, 129, 1553 (2007)

38. S.-H. Tung, Y.-E. Huang, S. R. Raghavan

Contrasting effects of temperature on the rheology of normal and reverse wormlike micelles.
Langmuir, 23, 372 (2007)

37. G. F. Payne and S. R. Raghavan

Chitosan: A soft interconnect for hierarchical assembly of nanoscale components.
Soft Matter, 2, 521 (2007) (Cover)

36. C. Zhu, L-Q. Wu,…S. R. Raghavan, G. F. Payne

Reversible vesicle restraint in response to spatiotemporally-controlled electrical signals.
Langmuir, 23, 286 (2007)

Paper 43

Wormlike micelles of a zwitterionic surfactant: From viscoelastic solutions to elastic gels.

This study demonstrates for the first time that ‘wormlike micelles’ (long self-assembled chains) can be formed in water by a zwitterionic surfactant (i.e., one with both cationic and anionic moieties in its head group). The micellar samples behave as elastic gels at room temperature, as seen from the above photo where the sample holds its weight in the inverted vial. The sample also maintains its viscoelasticity even up to high temperatures (~ 90°C).

Citations: > 200 (Google Scholar)

Paper 39

A simple class of photorheological fluids: Solutions with viscosity tunable by light.

This paper, for the first time, enables one to easily create an aqueous fluid whose viscosity could be radically altered by shining light. The fluid contains surfactant molecules that self-assemble into long chains (wormlike micelles) initially. Irradiation with UV light alters the geometry of the surfactants, which makes them re-assemble into spherical micelles, causing a 10,000-fold drop in viscosity.

This work was highlighted in a variety of scientific media including Nature Materials and Materials Today.

Citations: > 200 (Google Scholar)

2006

35. X. Huang, S. R. Raghavan, P. Terech, R. G. Weiss

Distinct kinetic pathways generate organogel networks with contrasting fractality and thixotropy.
JACS 128, 15341 (2006)

34. X. Wang,…J. H. Lee, S. R. Raghavan, D. S. English

Highly efficient capture and long-term encapsulation of dye by catanionic surfactant vesicles.
Langmuir 22, 6461 (2006)

33. T. S. Davies, A. M. Ketner, S. R. Raghavan

Self-assembly of surfactant vesicles that transform into viscoelastic wormlike micelles upon heating.
JACS 128, 6669 (2006)

32. S.-H. Tung, Y.-E. Huang, S. R. Raghavan

A new reverse wormlike micellar system: Mixtures of bile salt and lecithin in organic liquids.
JACS 128, 5751 (2006)

31. D. R. Strachan, G. C. Kalur, S. R. Raghavan

Size-dependent diffusion in an aging colloidal glass.
Physical Review E 73, 041509 (2006)

30. C. Zhu, J. H. Lee, S. R. Raghavan, G. F. Payne

Bio-inspired vesicle restraint and mobilization using a biopolymer scaffold.
Langmuir 22, 2951 (2006)

29. P. Elkouss, D. I. Bigio,…S. R. Raghavan

Influence of polymer viscoelasticity on the residence distributions of extruders.
AIChE Journal 52, 1451 (2006)

28. J. H. Lee, V. Agarwal,…S. R. Raghavan

Transition from unilamellar to bilamellar vesicles induced by an amphiphilic biopolymer.
Physical Review Letters 96, 048102 (2006)

Paper 33

Self-assembly of vesicles that transform into viscoelastic micelles upon heating.

This paper reports an unusual phenomenon where the viscosity of a solution increases 1000-fold upon heating. It is shown to be due to a self-assembly transition in water from vesicles (i.e., discrete spheres) at low temperatures to ‘wormlike micelles’ (i.e., long, entangled chains) at high temperatures.

Citations: > 400 (Google Scholar)

Paper 28

Transition from unilamellar to bilamellar vesicles induced by an amphiphilic biopolymer.

This paper continues our study on the self-assembly of a biopolymer with hydrophobic side-chains when combined with vesicles. The remarkable result is that the biopolymer can sometimes convert unilamellar vesicles (i.e., hollow spheres with a single outer shell) to bilamellar vesicles (i.e., with two concentric shells). The latter are shown in the image above. Examples of bilamellar structures include the nucleus and mitochondria in our cells.

Paper 32

A new reverse wormlike micellar system: Mixtures of bile salt and lecithin in organic liquids.

Self-assembly in oil (nonpolar organic liquids) has not been studied to the same extent as in water. This paper describes a new way to induce self-assembly of long chains (‘reverse wormlike micelles’) in oil: it involves mixing a lipid with bile salts. Both lipids and bile salts are biomolecules that are found in our body.

Citations: > 150 (Google Scholar)

2005

27. G. C. Kalur, B. D. Frounfelker,…S. R. Raghavan

Viscosity increase with temperature in surfactant solutions due to the growth of wormlike micelles.
Langmuir 21, 10998 (2005)

26. A. F. Kostko,…M. Anisimov,…S. R. Raghavan

Salt effects on the phase behavior, structure, and rheology of chromonic liquid crystals.
Journal of Physical Chemistry B 109, 19126 (2005)

25. B. H. Cipriano, S. R. Raghavan, P. M. McGuiggan

Surface tension and contact angle measurements of an imidazolium surfactant adsorbed on clay.
Colloids and Surfaces A 262, 8 (2005)

24. P. A. Hassan,…S. K. Kulshreshtha, S. R. Raghavan

Microrheology of wormlike micellar fluids from the diffusion of colloidal probes.
Journal of Physical Chemistry B 109, 8744 (2005)

23. G. C. Kalur and S. R. Raghavan

Anionic wormlike micellar fluids that display cloud points: Rheology and phase behavior.
Journal of Physical Chemistry B 109, 8599 (2005)

22. X. Huang, P. Terech, S. R. Raghavan, R. G. Weiss

Kinetics and structure of carbamate/n-alkane organogels and their fibrillar networks.
JACS 127, 4336 (2005)

21. J. H. Lee, J. Gustin,…S. R. Raghavan

Vesicle-biopolymer gels: Networks of surfactant vesicles connected by associating biopolymers.
Langmuir 21, 26 (2005)

Paper 27

Viscosity increase with temperature due to the growth of wormlike micelles.

This paper documents an unusual effect: an increase in solution viscosity with temperature. The solutions contain a cationic surfactant and a naphthalene salt, which together form ‘wormlike micelles’. The micelles are shown to increase in length upon heating, which thereby causes the viscosity to rise.

Citations: > 150 (Google Scholar)

Paper 26

Salt effects on the phase behavior, structure, and rheology of chromonic liquid crystals

Cromolyn is an aromatic molecule that assembles into columns in water, which in turn align into nematic liquid crystals (LCs). These LCs reveal beautiful textures under polarized light microscopy. This paper shows that NaCl promotes the growth of the columns and thus widens the range of nematic behavior.

Citations: > 100 (Google Scholar)

Paper 23

Anionic wormlike micellar fluids that display cloud points

This is the first study to show that ‘wormlike micelles’ (self-assembled chains) can be formed by anionic surfactants. The surfactant here is sodium oleate and it forms worms when combined with various salts. Worms formed using triethylamine salts exhibit clouding, i.e., phase separation, upon heating.

Citations: > 150 (Google Scholar)

Paper 21

Vesicle-biopolymer gels: Networks of vesicles connected by associating biopolymers.

This paper shows that chains of a biopolymer with hydrophobic side-chains can connect vesicles into a network, i.e., into a ‘vesicle gel‘. The gel holds its weight in the inverted vial in the above image. The driving force for this self-assembly is hydrophobic interactions between the polymer and the vesicles.

Citations: > 150 (Google Scholar)