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Abstract: Directional freezing is a simple and environmentally friendly method for producing aligned porous materials. Porous structures of uniaxially aligned nanoparticles can be produced by unidirectional freezing a concentrated nanoparticle dispersion and subsequent freeze-drying. However, mechanically strong through-thickness membranes have seldom been reported. The film prepared by directional freezing and subsequent freeze-drying is usually too weak to be a free-standing membrane. By using precise control of freezing rate and direction, we successfully produced free-standing films (with 20–200 μm thickness and 40–60 vol% through-thickness porosity) from inorganic particles/polymer (polytetrafluoroethylene and polyvinylidene fluoride) composites. The pore size could be conveniently controlled by freezing rate and dispersion concentration. The use of composite materials, emulsion states, and post-annealing processes facilitated the preparation of free-standing two-dimensional particulate networks due to enhanced interparticulate coherence. This method could provide novel porous networks with controlled morphology, reduced tortuosity, and enhanced mechanical properties, which have broad applications such as separation/purification, fuel cells, nanocomposites, catalysts, tissue engineering, controlled delivery, and other medical applications. [ABSTRACT FROM AUTHOR]

The article discusses the study of the electrothermal soft manipulator enabling safe transport and handling of thin cell/tissue sheets and bioelectronic devices. Topics discusses include this study presents a soft manipulator that can manipulate and transport cell/tissue sheets and ultrathin wearable biosensing devices seamlessly; and the soft manipulator consists of an ultrafast thermo-responsive, microchanneled hydrogel layer with tissue-like softness and an electric heater layer.

Abstract The recent rapid development of soft electronics and wearable technology has demanded materials with the function of combining mechanical deformation and electronics. Particularly, materials simultaneously having memory shape characteristics in which mechanical deformation repeatedly occurs in response to stimulus, high stretchability and excellent electric/heat transfer characteristics are interesting actuator materials in future applications. As a stretchable and conductive platform, we fabricated a reentrant micro-honeycomb structure from graphene-CNT, which had structural stretchability due to the accordion-like reentrant structure and continuous conductive paths in the vertical and horizontal directions. To impart shape memory properties, we fabricated composites by simply infiltrating shape memory polyurethane (SMPU) into a stable graphene/CNT framework. Our resulting reentrant micro-honeycomb graphene-CNT/SMPU composites simultaneously exhibited a relatively low resistivity of 5 Ω cm, a change in resistance of less than 10% in the 50% stretching/releasing states, long term stability, and superior tensile shape memory properties, including 95.6% shape fixity and a 90.6% recovery ratio. Regularly distributed graphene-CNT structures offer heterogeneous nucleation sites and undisturbed crystal growth in neat SMPU pillars, resulting in superior shape memory properties. We also constructed a circuit with portable batteries to demonstrate that our reentrant graphene-CNT/SMPU composite offers potential applications as an emergency circuit breaker. [ABSTRACT FROM AUTHOR]

Recently, numerous attempts have been made to engineer micro- and nano-porous surface patterns or to develop convenient preparation methods for the practical applications of self-cleaning surfaces, water-repellent surfaces, novel textures, etc. Herein, we introduce a simple, cheap, and repeatable crystallization-based method to produce porous surface structures, on any surface of already fabricated polymeric materials. Contact of the solvent phase with cooled polymer surfaces enabled the limited dissolution of the surfaces and the subsequent extremely fast melt crystallization of the solvent. After removing the crystals, various micro- and nano-porous patterns were obtained, whose pore sizes ranged over three orders of magnitude. Pore depth was linearly dependent on the dissolution time. Crystal growth was mainly directed normal to the surfaces, but it was also controlled in-plane, resulting in cylindrical or lamellar structures. Superhydrophobic surfaces were successfully prepared on both polystyrene and polycarbonate. This process offers a novel surface engineering tool for a variety of polymer surfaces, whose topology can be conveniently controlled over a wide range by crystal engineering. [ABSTRACT FROM AUTHOR]

A three dimensional reduced graphene oxide/polyurethane (RGO-PU) porous material with connected pores was prepared by physical adsorption of RGO onto the surface of porous PU. The porous PU was prepared by directional melt crystallization of a solvent, which produced high pores with controlled orientation. The prepared RGO-PU was characterized by scanning electron microscopy, spectroscopy and electro-chemical methods. The RGO-PU porous material revealed better electrochemical performance, which might be attributed to the robust structure, superior conductivity, large surface area, and good flexibility. Differential pulse voltammetry (DPV) analysis of DA using the RGO-PU exhibited a linear response range over a wide DA concentration of 100–1150 pM, with the detection limit of 1 pM. This sensor exhibited outstanding anti-interference ability towards co-existing molecules with good stability, sensitivity, and reproducibility. Furthermore, the fabricated sensor was successfully applied for the quantitative analysis of DA in human serum and urine samples with acceptable recovery, which indicates its feasibility for practical application. [ABSTRACT FROM AUTHOR]

Polystyrene (PS)/TiO 2 composite nanofiber membranes have been fabricated by electrospinning process for Cu 2+ ions removal from water. The surface properties of the polystyrene nanofibers were modulated by introducing TiO 2 nanoparticles. The contact angle of the PS nanofiber membrane was found to be decreased with increasing concentration of TiO 2 , depicted enhanced hydrophilicity. These membranes were highly effective in adsorbing Cu 2+ ions from water. The adsorption capacity of these membranes was found to be 522 mg/g, which is significantly higher than the results reported by other researchers. This was attributed to enhanced hydrophilicity of the PS/TiO 2 composite nanofiber membranes and effective adsorption property of TiO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

Living organisms secrete minerals composed of peptides and proteins, resulting in 'mesocrystals' of three-dimensional-assembled composite structures. Recently, this biomimetic polymer-directed crystallization technique has been widely applied to inorganic materials, although it has seldom been used with drugs. In this study, the technique was applied to the drowning-out crystallization of atorvastatin using various polymers. Nucleation and growth at optimized conditions successfully produced composite crystals with significant polymer contents and unusual characteristics. Atorvastatin composite crystals containing polyethylene glycol, polyacrylic acid, polyethylene imine, and chitosan showed a markedly decreased melting point and heat of fusion, improved stability, and sustained-release patterns. The use of hydroxypropyl cellulose yielded a unique combination of enhanced in vitro release and improved drug stability under a forced degradation condition. The formation hypothesis of unique mesocrystal structures was strongly supported by an X-ray diffraction pattern and substantial melting point reduction. This polymer-directed crystallization technique offers a novel and effective way, different from the solid dispersion approach, to engineer the release, stability, and processability of drug crystals. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:2941-2951, 2012 [ABSTRACT FROM AUTHOR]