Spray-Processed Composites with High Conductivity and Elasticity.

Highly conductive elastic composites were constructed using multistep solution-based fabrication methods that included the deposition of a nonwoven polymer fiber mat through solution blow spinning and nanoparticle nucleation. High nanoparticle loading was achieved by introducing silver nanoparticles into the fiber spinning solution. The presence of the silver nanoparticles facilitates improved uptake of silver nanoparticle precursor in subsequent processing steps. The precursor is used to generate a second nanoparticle population, leading to high loading and conductivity. Establishing high nanoparticle loading in a microfibrous block copolymer network generated deformable composites that can sustain electrical conductivities reaching 9000 S/cm under 100% tensile strain. These conductive elastic fabrics can retain at least 70% of their initial electrical conductivity after being stretched to 100% strain and released for 500 cycles. This composite material system has the potential to be implemented in wearable electronics and robotic systems.

Simple and inexpensive quantification of ammonia in whole blood.

Quantification of ammonia in whole blood has applications in the diagnosis and management of many hepatic diseases, including cirrhosis and rare urea cycle disorders, amounting to more than 5 million patients in the United States. Current techniques for ammonia measurement suffer from limited range, poor resolution, false positives or large, complex sensor set-ups. Here we demonstrate a technique utilizing inexpensive reagents and simple methods for quantifying ammonia in 100 µL of whole blood. The sensor comprises a modified form of the indophenol reaction, which resists sources of destructive interference in blood, in conjunction with a cation-exchange membrane. The presented sensing scheme is selective against other amine containing molecules such as amino acids and has a shelf life of at least 50 days. Additionally, the resulting system has high sensitivity and allows for the accurate reliable quantification of ammonia in whole human blood samples at a minimum range of 25 to 500 µM, which is clinically for rare hyperammonemic disorders and liver disease. Furthermore, concentrations of 50 and 100 µM ammonia could be reliably discerned with p = 0.0001.

Sprayable elastic conductors based on block copolymer silver nanoparticle composites.

Block copolymer silver nanoparticle composite elastic conductors were fabricated through solution blow spinning and subsequent nanoparticle nucleation. The reported technique allows for conformal deposition onto nonplanar substrates. We additionally demonstrated the ability to tune the strain dependence of the electrical properties by adjusting nanoparticle precursor concentration or localized nanoparticle nucleation. The stretchable fiber mats were able to display electrical conductivity values as high as 2000 ± 200 S/cm with only a 12% increase in resistance after 400 cycles of 150% strain. Stretchable elastic conductors with similar and higher bulk conductivity have not achieved comparable stability of electrical properties. These unique electromechanical characteristics are primarily the result of structural changes during mechanical deformation. The versatility of this approach was demonstrated by constructing a stretchable light emitting diode circuit and a strain sensor on planar and nonplanar substrates.