Electrode-free picoinjection of microfluidic drops.

Existing methods for injecting reagents into drops utilize metal electrodes integrated into the microfluidic chip, adding cumbersome and error-prone steps to the fabrication process. Here, we introduce a method that uses the injection fluid itself as an electrode by exploiting dissolved electrolytes in the solution. This obviates the need for metal electrodes and reduces fabrication time and complexity while also affording precise control of the injected reagent volumes.