Ultrafast vapourization dynamics of laser-activated polymeric microcapsules.

Precision control of vapourization, both in space and time, has many potential applications; however, the physical mechanisms underlying controlled boiling are not well understood. The reason is the combined microscopic length scales and ultrashort timescales associated with the initiation and subsequent dynamical behaviour of the vapour bubbles formed. Here we study the nanoseconds vapour bubble dynamics of laser-heated single oil-filled microcapsules using coupled optical and acoustic detection.

Influence of shell properties on high-frequency ultrasound imaging and drug delivery using polymer-shelled microbubbles.

This two-part study investigated shell rupture of ultrasound contrast agents (UCAs) under static overpressure conditions and the subharmonic component from UCAs subjected to 20-MHz tonebursts. Five different polylactide-shelled UCAs with shell-thickness-to-radius ratios (STRRs) of 7.5, 30, 40, 65, and 100 nm/¿m were subjected to static overpressure in a glycerol-filled test chamber.

Monodisperse polymeric particles prepared by ink-jet printing: double emulsions, hydrogels and polymer mixtures.

Submerged ink-jetting produces a monodisperse emulsion that can be converted into monodisperse particles. As the initial droplet size is known and the final particle size can be easily measured, such a method can be used to quantify the shrinkage and the swelling of polymer particles made from double emulsions, polymer mixtures and hydrogel forming polymers. It is found that at the same starting concentration and initial emulsion droplet size poly-lactide-co-glycolide particles made from an ink-jetted emulsion have the same size as particles ink-jetted from a solution, however with a more porous structure.

Effect of molecular weight, crystallinity, and hydrophobicity on the acoustic activation of polymer-shelled ultrasound contrast agents.

Polymer-shelled microbubbles are applied as ultrasound contrast agents. To investigate the effect of the polymer on microbubble preparation and acoustic properties, polylactides with systematic variations in molecular weight, crystallinity, and end-group hydrophobicity were used. Polymer-shelled cyclodecane filled capsules were prepared by emulsification, and the cyclodecane was removed by lyophilization to obtain hollow capsules.

Oil-filled polymer microcapsules for ultrasound-mediated delivery of lipophilic drugs.

The use of ultrasound contrast agents as local drug delivery systems continues to grow. Current limitations are the amount of drug that can be incorporated as well as the efficiency of drug release upon insonification. This study focuses on the synthesis and characterisation of novel polymeric microcapsules for ultrasound-triggered delivery of lipophilic drugs.

Large area liquid crystal monodomain field-effect transistors.

Butyl, hexyl, and decyl derivatives of the liquid-crystalline organic semiconductor 5,5' '-bis(5-alkyl-2-thienylethynyl)-2,2':5',2' '-terthiophene were synthesized and studied with respect to their structural, optical, and electrical properties. By means of an optimized thermal annealing scheme the hexyl and decyl compounds could be processed into self-assembled monodomain films of up to 150 mm in diameter. These were investigated with X-ray diffractometry, which revealed a clearly single-crystalline monoclinic morphology with lamellae parallel to the substrate.