A miniature version of a ubiquitous laboratory instrument could move chemistry experiments out of test tubes and into tiny droplets. Researchers report that they have engineered a pipette that can dispense solutions at volumes of a billionth of a billionth of a liter.
The nanopipette consists of a millimeter-diameter glass tube that contains two chambers. The tube ends at a fine tip with two holes, one per chamber and each roughly 100 nanometers across. Each chamber holds an electrode and a conductive solution of water and salt.
A computer applies a voltage to the chambers, starting a current that flows from one chamber to the other. Voltages from 25 to 100 volts move liquid out of the chambers, forming a single droplet. As the group had shown in previous work, voltages of 1 to 2 V move only molecules, but no liquid, out of the pipette openings.
The researchers, led by David Klenerman of the University of Cambridge in England, performed chemical reactions in their minuscule droplets. In one experiment, the nanopipette dispensed chemicals and the enzyme that catalyzed their reaction in the tiny droplet to form a fluorescent product, the team reports in an upcoming Nano Letters.
Klenerman would like to automate the system and build nanopipette arrays that can produce thousands of small droplets at a time. Such work could lead to “highly miniaturized chemistry” in volumes similar to those within individual living cells, he says.