Microinjectors are provided. A microinjector includes a substrate, a manifold formed on the substrate, and at least a jet unit. The jet unit includes a nozzle layer connected to the substrate, a nozzle disposed on the nozzle layer, a reservoir, a first heater disposed on a first side of the nozzle and a second heater disposed on a second side of the nozzle. The reservoir is formed between the nozzle layer and the substrate, connecting the nozzle and the manifold. Specifically, the first and second heaters are actuated by individual drive circuits, to heat the reservoir and eject a droplet through the nozzle.