A New Class Of Soft Dendritic Colloidal Microgels With Extraordinary Gelation And Adhesive Capabilities

The interplay between morphology, excluded volume, and adhesivity of colloidal-scale particles critically determines the physical properties of numerous materials such as gels, suspensions, emulsions, foams, and coatings. The structure-building and gel-forming abilities of colloids in liquid can be enhanced by particles with branched and fractal morphology. We will present a new class of soft dendritic colloids (“dendricolloids”) that are fabricated by a simple and scalable process of polymer precipitation in turbulently sheared liquid medium. These new soft particles have a hierarchical morphology similar to molecular-scale polymer dendrimers, but two orders of magnitude larger in scale. The polymer microgel-like particle with branched and fractal morphology are formed as a result of the eddy-guided polymer precipitation in turbulently sheared liquid. The ultralow interfacial tension of a polymer solution, combined with concurrent phase separation and precipitation, results in the formation of hierarchical fibrillar polymer microgels. The branched, dendritic particles are surrounded by a corona of polymer nanofibers spreading out in all directions. The dendricolloids combine the properties of two of the most fascinating and studied soft matter systems – the freely-suspended dendritic particles have very large excluded volume, while on contact their nanofiber corona possesses the highly adhesive abilities of the nanofiber-padded gecko legs. We investigate and analyze the origins of these effects, which are closely associated with omnipresent van der Waals forces and the phenomenon of “contact splitting” that allows the legs of the gecko lizards to stick to any surface. The fractal branching and contact splitting phenomena of the polymer dendricolloids enable a range of highly unusual properties – gelation at extremely low volume fractions, strong adhesion to surfaces and to each other, and ability to bind strongly and form coatings, nonwoven sheets, and ultrasoft membranes. Please click Additional Files below to see the full abstract

Transparent and soft elastomeric composites and oil/water biphasic systems with stimuli-triggered release of “invisible” liquid

The synthesis, principles, and properties of a new class of stimuli-responsive soft matter biphasic composites will be introduced. The soft composite consists of more than 30% of aqueous solution emulsion (of micron-sized droplets) optically hidden in a matrix of silicone or hydrocarbon gel. Through delicate adjustment of the refractive index (RI) of the internal aqueous phase, the composite is completely transparent to visible light and the internally dispersed aqueous droplet phase is invisible to the naked eye. Multiple phases can be included in the form of gelled multiple emulsion. The composite exhibits unique stimuli-response capabilities, such as changing its optical transmittance upon mechanical, thermal, osmotic and other stresses. Intrusion damage causes the composite to release the RI matched aqueous phase, which causes change in transparency of color. In addition, when the composite is present in an aqueous medium where salinity is different from the dispersed phase, the osmotic pressure in the droplets causes instantaneous transparency change triggered by osmotic pressure. This enables us to measure osmotic pressure of the aqueous medium quickly. The new composites and gels could find many applications including a number of cosmetics and other consumer products with attractive and unusual appearance and stimulus-triggered active ingredients delivery. Please click Additional Files below to see the full abstract

A new class of dendrimeric gecko legs polymer particles with extraordinary structure- building, gelation and adhesive capabilities

Particulate rheology modifiers are important component of many cosmetics, food, and pharmaceutical formulations. The efficiency of rheology modifiers is usually determined by the interplay between surface area and shape of suspended particles. We will present a new class of nanofibrilated dendrimeric polymer particles (DPPs) with very high surface area and morphology engineered for applications in rheology modifiers and adhesives. The DPPs are fabricated in a novel efficient and scalable process for liquid-based synthesis of nanomaterials by antisolvent precipitation in turbulently sheared medium. The process allows for a variety of polymers to be readily made into DPPs which are hierarchically structured, with a big branched corona of nanofibers spreading out in all directions. The hierarchical structure endows DPPs with high excluded volume. They build a stable three-dimensional network leading to gel-like behavior at fractions as low as 1-2 vol.% of DPPs in various liquids. In addition, the biomimetic similarity of their structure to the gecko lizards’ setae endows the DPPs with excellent adhesion and cohesion properties. Our results demonstrate that this strong adhesion and cohesion are attributed to the contact splitting and van der Waals interactions of their nanofibrous structures. This new class of polymeric particles opens new ways to make strong non-covalent binding coatings, new types of dry adhesives, nonwovens and fluid-gels. They could have a transformative role as rheology modifiers and nano-adhesives to hair and skin in many cosmetics formulations. Please click Additional Files below to see the full abstract

Relationship between residential district and health-related quality of life in Chungnam industrial complex area

Objectives This study aimed to evaluate the relationship between residential district of people, such as power plant, steel-mill and petrochemical industries, and health-related quality of life (HRQoL). Methods Using a cross-sectional study design, we randomly recruited participants for our study from industrial areas (thermoelectric power plant, steel-mill, petrochemical industry) and rural areas. Logistic regression analysis was used to identify the relationships between Euro quality of life-5 dimension (EQ-5D) scores and living region, while controlling for sociodemographic characteristics. Results In adjusted model, quality of life decreased with increasing category of age and were lower for females than males. EQ-5D scores of people living in the vicinity of thermoelectric power plant were significant lower than those of people living the vicinity of comparison region (odds ratio, 1.59; 95% confidence interval, 1.00 to 2.53). Conclusions Living region of thermoelectric power plant, was strongly associated with scores on the EQ-5D. More research is needed to elucidate the mechanisms which makes the relationship with the living regions and HRQoL

Risk factors associated with depression and suicidal ideation in a rural population

Objectives This study aimed to evaluate the risk factors associated with depression and suicidal ideation in a rural population. Methods A survey was conducted with 543 farmers from Chungcheongnam-do Province using the Center for Epidemiologic Studies Depression Scale (CES-D) for depression, Lubben Social Network Scale (LSNS) for social support, Swedish Q16 for neurotoxicity symptoms and a survey tool for farmer’s syndrome. Results After adjusting for socioeconomic factors using logistic regression analysis, poor self-rated health, low social support and neurotoxicity were positively associated with the risk of depression (odds ratio [OR], 15.96; 95% confidence interval [CI], 3.11 to 81.97; OR, 3.14; 95% CI, 1.26 to 7.82; and OR, 3.68; 95% CI, 1.08 to 12.57, respectively). The risk of suicidal ideation significantly increased with low social support, neurotoxicity and farmer’s syndrome (OR, 2.28; 95% CI, 1.18 to 4.40; OR, 6.17; 95% CI, 2.85 to 13.34; and OR, 3.70; 95% CI, 1.51 to 9.07, respectively). Conclusions Given the overall results of this study, there is a need to establish programs which can improve the health and social relationships of farmers. Also, when farmers have neurological symptoms from pesticide exposure and characteristic symptoms of farmer’s syndrome, a monitoring system for depression and suicide must be made available.Conclusions: Given the overall results of this study, there is a need to establish programs which can improve the health and social relationships of farmers. Also, when farmers have neurological symptoms from pesticide exposure and characteristic symptoms of farmer's syndrome, a monitoring system for depression and suicide must be made available

Sharing of Strain Between Nanofiber Forests and Liquid Crystals Leads to Programmable Responses to Electric Fields

Fibers embedded in soft matrices are widely encountered in biological systems, with the fibers providing mechanical reinforcement or encoding of instructions for shape changes. Here, the mechanical coupling of end-attached polymeric nanofiber forests and liquid crystals (LCs) is explored, where the nanofibers are templated into prescribed shapes by the chemical vapor polymerization of paracyclophane-based monomers in supported films of the LCs. It is shown that the elastic energies of the nanofibers and LCs are comparable in magnitude, leading to reversible straining of nanofibers via the application of an electric field to the LC. This coupling is shown to encode complex electrooptical responses in the LC (e.g., optical vortices), thus illustrating how LC-templated nanofiber forests offer the basis of fresh approaches for programming configurational changes in soft materials.Polymeric end-attached nanofibers are synthesized by chemical vapor polymerization within liquid crystalline films and are shown to encode complex mechanical and optical responses upon the application of an electric field. The responses arise from a sharing of elastic strain between the nanofibers and liquid crystal, and they appear promising for programming soft actuators and optical devices.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/173026/1/adfm202200830-sup-0001-SuppMat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/173026/2/adfm202200830.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/173026/3/adfm202200830_am.pd

3D Printing by Multiphase Silicone/Water Capillary Inks

3D printing of polymers is accomplished easily with thermoplastics as the extruded hot melt solidifies rapidly during the printing process. Printing with liquid polymer precursors is more challenging due to their longer curing times. One curable liquid polymer of specific interest is polydimethylsiloxane (PDMS). This study demonstrates a new efficient technique for 3D printing with PDMS by using a capillary suspension ink containing PDMS in the form of both precured microbeads and uncured liquid precursor, dispersed in water as continuous medium. The PDMS microbeads are held together in thixotropic granular paste by capillary attraction induced by the liquid precursor. These capillary suspensions possess high storage moduli and yield stresses that are needed for direct ink writing. They could be 3D printed and cured both in air and under water. The resulting PDMS structures are remarkably elastic, flexible, and extensible. As the ink is made of porous, biocompatible silicone that can be printed directly inside aqueous medium, it can be used in 3D printed biomedical products, or in applications such as direct printing of bioscaffolds on live tissue. This study demonstrates a number of examples using the high softness, elasticity, and resilience of these 3D printed structures

Soft dendritic microparticles with unusual adhesion and structuring properties

The interplay between morphology, excluded volume and adhesivity of particles critically determines the physical properties of numerous soft materials and coatings1–6. Branched particles2 or nanofibres3, nanofibrillated cellulose4 or fumed silica5 can enhance the structure-building abilities of colloids, whose adhesion may also be increased by capillarity or binding agents6. Nonetheless, alternative mechanisms of strong adhesion found in nature involve fibrillar mats with numerous subcontacts (contact splitting)7–11 as seen in the feet of gecko lizards and spider webs12–17. Here, we describe the fabrication of hierarchically structured polymeric microparticles having branched nanofibre coronas with a dendritic morphology. Polymer precipitation in highly turbulent flow results in microparticles with fractal branching and nanofibrillar contact splitting that exhibit gelation at very low volume fractions, strong interparticle adhesion and binding into coatings and non-woven sheets. These soft dendritic particles also have potential advantages for food, personal care or pharmaceutical product formulations.</p

Fluid Flow Templating of Polymeric Soft Matter with Diverse Morphologies

It is challenging to find a conventional nanofabrication technique that can consistently produce soft polymeric matter of high surface area and nanoscale morphology in a way that is scalable, versatile, and easily tunable. Here, the capabilities of a universal method for fabricating diverse nano- and micro-scale morphologies based on polymer precipitation templated by the fluid streamlines in multiphasic flow are explored. It is shown that while the procedure is operationally simple, various combinations of its intertwined mechanisms can controllably and reproducibly lead to the formation of an extraordinary wide range of colloidal morphologies. By systematically investigating the process conditions, 12 distinct classes of polymer micro- and nano-structures including particles, rods, ribbons, nanosheets, and soft dendritic colloids (dendricolloids) are identified. The outcomes are interpreted by delineating the physical processes into three stages: hydrodynamic shear, capillary and mechanical breakup, and polymer precipitation rate. The insights into the underlying fundamental mechanisms provide guidance toward developing a versatile and scalable nanofabrication platform. It is verified that the liquid shear-based technique is versatile and works well with many chemically diverse polymers and biopolymers, showing potential as a universal tool for simple and scalable nanofabrication of many morphologically distinct soft matter classes

Printable homocomposite hydrogels with synergistically reinforced molecular-colloidal networks

The design of hydrogels where multiple interpenetrating networks enable enhanced mechanical properties can broaden their field of application in biomedical materials, 3D printing, and soft robotics. We report a class of self-reinforced homocomposite hydrogels (HHGs) comprised of interpenetrating networks of multiscale hierarchy. A molecular alginate gel is reinforced by a colloidal network of hierarchically branched alginate soft dendritic colloids (SDCs). The reinforcement of the molecular gel with the nanofibrillar SDC network of the same biopolymer results in a remarkable increase of the HHG’s mechanical properties. The viscoelastic HHGs show >3× larger storage modulus and >4× larger Young’s modulus than either constitutive network at the same concentration. Such synergistically enforced colloidal-molecular HHGs open up numerous opportunities for formulation of biocompatible gels with robust structure-property relationships. Balance of the ratio of their precursors facilitates precise control of the yield stress and rate of self-reinforcement, enabling efficient extrusion 3D printing of HHGs.</p