Isotachophoresis can be employed to simultaneously focus the target and ligand of an assay into the same ITP focus zone. The methods include removing a cassette of gears from the hub of a bicycle gear and installing a single gear between two clamps that are releasably secured to the hub. A one-piece C-section metal bar is snugly received in the mouth slot. Other embodiments are described and claimed. In a method for operating an LED, the LED is modulated by alternating the switching device between a closed state and an open state.