Giant volume change of active gels under continuous flow.

While living systems have developed highly efficient ways to convert chemical energy (e.g., ATP hydrolysis) to mechanical motion (e.g., movement of muscle), it remains a challenge to build muscle-like biomimetic systems to generate mechanical force directly from chemical reactions. Here we show that a continuous flow of reactant solution leads to by far the largest volume change to date in autonomous active gels driven by the Belousov-Zhabotinsky reaction. These results demonstrate that microfluidics offers a useful and facile experimental approach to optimize the conditions (e.g., fabrication methods, counterions, flow rates, concentrations of reagents) for chemomechanical transduction in active materials. This work thus provides much needed insights and methods for the development of chemomechanically active systems based on combining soft materials and microfluidic systems.

Strategies for the analysis of highly reactive pinacolboronate esters.

Pinacolboronate esters (or boronic acid, pinacol esters) are widely used in the Suzuki coupling reaction to connect organic building blocks for the total synthesis of complex molecules. The 2-aminopyrimidine-5-pinacolboronate ester was used as a starting material in the synthesis of a development compound, necessitating a chromatographic purity method to assess its quality. This aryl pinacolboronate ester posed unique analytical challenges due to its facile hydrolysis to the corresponding boronic acid, which is nonvolatile and poorly soluble in organic solvents. This made GC and normal-phase HPLC analysis unsuitable. In reversed-phase mode, typical sample preparation and analysis conditions promoted rapid sample degradation to the boronic acid. To overcome these challenges, unconventional approaches were necessary in order to stabilize 2-aminopyrimidine-5-pinacolboronate ester, adequately solubilize its boronic acid, and produce acceptable separation and retention. The final method employed non-aqueous and aprotic diluent, and a reversed-phase separation using highly basic mobile phases (pH 12.4) with an ion pairing reagent. These strategies were successfully applied to several other reactive pinacolboronate esters for purity analysis, demonstrating broad applicability to this unique class of compounds.