Stretchable conductive polypyrrole/polyurethane (PPy/PU) strain sensor with netlike microcracks for human breath detection.

The development of wearable electronics that can monitor human physiological information demands specially structured materials with excellent stretchability and electrical conductivity. In this study, a new stretchable conductive polypyrrole/polyurethane (PPy/PU) elastomer was designed and prepared by surface diffusion and in situ polymerization of PPy inside and on porous PU substrates. The structures allowed the formation of netlike microcracks under stretching. The netlike microcrack structures make possible the reversible changes in the electrical resistance of PPy/PU elastomers under stretching and releasing cycles. The variations in morphology and chemical structures, stretchability, and conductivity as well as the sensitivity of resistance change under stretching cycles were investigated. The mechanism of reversible conductivity of the PPy/PU elastomer was proposed. This property was then used to construct a waistband-like human breath detector. The results demonstrated its potential as a strain sensor for human health care applications by showing reversible resistance changes in the repeated stretching and contracting motion when human breathes in and out.

Removal of benzene and toluene in polyurethane biofilter immobilized with Rhodococcus sp. EH831 under transient loading.

The performance of a polyurethane (PU) biofilter inoculated with Rhodococcus sp. EH831 was evaluated under different transient loading conditions, such as shutdown, intermittent and fluctuating loading. A mixture of benzene and toluene vapors was employed as model pollutants. When the biofilter was restarted after a 2 week-shutdown, during which neither clean air nor water was supplied, the benzene and toluene removal capacities were rapidly restored after a re-adaptation period of only 1 day. A comparison of the removal capacity under continuous and intermittent loading revealed that constant and periodic loading (8 h on/16 h off per day) and a 2 day-shutdown did not significantly influence the biofilter performance, although the removals of benzene and toluene were relatively unstable and lower under intermittent loading during the initial week. The result of quantitative real-time PCR showed that Rhodococcus sp. EH831 could be maintained during transient loading periods (10(10)-10(11) CFU/g-dry PU) irrespective of the different operating conditions.

New indole-based chromophore-containing main-chain polyurethanes: architectural modification of isolation group, enhanced nonlinear optical property, and improved optical transparency.

Three indole-based nonlinear optical (NLO) chromophores with changeable isolation groups were successfully introduced into the polymer backbone to yield a series of main-chain polyurethanes. Thanks to the main-chain structure and the advantages of the indole-based chromophores, all of the polymers show excellent transparency, good processability, thermal stability, and relatively good NLO effects. The obtained experimental results indicated that the polymer backbone, in addition to the linked isolation moieties, could act as isolation spacers in some special cases. The tested NLO results demonstrated that the isolation groups with apparent site-isolation effect might not benefit the macroscopic NLO effect of the resultant polymers.

Biocompatibility of poly(carbonate urethane)s with various degrees of nanophase separation.

Nanophase separation has been suggested to influence the biological performance of polyurethane. In a previous work, six different 4,4'-diphenylmethane diisocyanate (MDI)-based poly(carbonate urethane)s (PCUs) that exhibited various degrees of nanophase separation were synthesized and characterized. In the present work, these PCUs were used as a model system to study the effect of nanometric structures on the biocompatibility of polyurethane. Human blood platelet activation, monocyte activation, protein adsorption, and bacterial adhesion on PCU were investigated in vitro. It was found that human blood platelets as well as monocytes were less activated on the PCU surfaces with a greater degree of nanophase separation in general. This phenomenon was closely associated with the lower ratio of human fibrinogen/albumin competitively adsorbed on these surfaces. Bacterial adhesion was also inhibited in some nanophase-separated PCUs. [diagram in text].

Calcium effect on the membrane preparation of segmented poly(ether/urethane/amide) (PEUN) as a biomedical material.

Poly(ether/urethane/amide) (PEUN), a segmented polyurethane, was characterized concerning phase relationship, viscosity in solution, hydraulic permeability, mechanical properties, and in vivo biocompatibility with tissue and blood. PEUN was dissolved at the highest concentration of 0.5% in N,N-dimethylformamide (DMF). Addition of calcium chloride at concentrations up to 3.1% progressively increased the solubility of PEUN in DMF PEUN2 membrane was prepared by casting from mixtures of PEUN, 3% calcium chloride, and DMF, from which calcium chloride was sufficiently removed. The PEUN2 membrane thus obtained was compared with PEUN membrane which was prepared by casting from DMF solution without the addition of calcium chloride. The water permeability across PEUN2 membrane was higher than that across PEUN membrane. PEUN2 membrane in the swollen state exhibited a lower tensile modulus and much greater elastic property than PEUN membrane. Tissue compatibility of PEUN2 membrane was better than that of PEUN membrane. Thromboresistance of PEUN membrane was good, while PEUN2-coated surface was thrombogenic to some extent in vivo. Our characterization suggested that PEUN2 membrane is more hydrophilic than PEUN membrane, possibly because of the assembly of polar groups on the segments of PEUN molecules which show affinity to calcium chloride in membrane processing.

Effect of toluene extraction on Biomer surface: II. An atomic force microscopy study.

The surface characterization of Biomer and extracted Biomer has been investigated using atomic force microscopy (AFM) in order to show the influence of extraction process on the morphology and local interactions which monitor surface properties at a molecular scale. The high viscoelasticity of these polymers provided by the soft segments makes AFM imaging in contact mode quite difficult, the scanning of the tip inducing artifacts on the surface. The rate, direction, and number of scans strongly influence this friction effect. The recording of force curves has shown that the extraction and conditions of drying can modify the interaction forces present at the polymer surface. Imaging of the extracted Biomer obtained with AFM in non-contact mode has revealed inclusion nodules embedded in an amorphous phase. This may be attributed to the migration at the surface of the non-eliminated poly(aminomethacrylate) additive.

Effect of toluene extraction on Biomer surface: I. ESCA, ATR/FTIR, contact angle analysis and biological properties.

Biomer is a poly(ether-urethane-urea) block copolymer widely used as biomedical devices. Extraction process of this polymer has purified its surface of low molecular weight polyurethane chains and Santowhite Powder additive. ESCA and ATR/FTIR have suggested a homogenization of the polymer by enrichment of the first layers with poly(aminomethacrylate) additive after extraction. Therefore, the surface of the extracted Biomer exhibits a different wettability and biological response. The treatment causes a significant decrease in fibronectin adsorption and induces a reduction in Staphylococcus aureus adhesion.