We report for the first time that conducting objects could be propelled in folded liquid filled channels by bipolar electrochemistry. This approach was based on controlling the formation of hydrogen bubbles at one extremity of a bipolar electrode. In this work, copper wires used as microswimmers could move in folded channels with angles from 30 to 180 by bubble propulsion and the velocity fluctuated over time. A proportional relation between polarization voltage and average velocity in linear channel was verified. The motion of microswimmers could be controlled within these types of channels in space and time, which might broaden the applications of micromachines in bipolar electrochemistry.

A high-speed separation method of capillary MEKC with LIF detection had been developed for separation and determination of amino acids in laver. The CE system comprised a manual slotted-vial array (SVA) for sample introduction that could improve the separation efficiency by reducing injection volume. Using a capillary with 80 mm effective separation length, the separation conditions for amino acids were optimized. Applied with the separation electric field strength of 300 V/cm, the ten amino acids could be completely separated within 2.5 min with 10 mol/L Na2HPO4-NaOH buffer (pH = 11.5) including 30 mmol/L SDS. Theoretical plates for amino acids ranged from 72,000 to 40,000 (corresponding to 1.1-2.0 μm plate heights) and the detection limits were between 25 and 80 nmol/L. Finally, this method was applied to analyze the composition of amino acids in laver and eight known amino acids could be found in the sample. The contents of five amino acids, tyrosine, glutamic acid, glycine, lysine, and aspartic acid that could be completely separated in real sample were determined. The recoveries ranged from 82.3% to 123% that indicated the good reliability for this method in laver sample analysis.

Alternate hot and cold electrodes, actively heated and chilled, were facilely fabricated for the first time. It consists of two symmetrically placed semiconductor thermoelectric coolers and an embedded interlayer with a Pt-PtRh thermocouple. The tip of Pt-PtRh thermocouple can be used as both an electrochemical electrode and a temperature sensing device simultaneously. Theoretical simulation shows that a local steady-state supercooled water within a radius of ca. 12.6 mm around the electrode can be obtained. In this paper, the activity of horseradish peroxidase is evidenced at supercooled temperature (9 o C) in 0.1 M PBS.

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