Feedback controllers (which act like Maxwell's demon) can extract useful work by rectifying thermal fluctuations. However, feedback controllers consume energy, and the work extracted cannot compensate the energy consumed. In this paper, we propose a molecular ratchet model without any feedback controllers and report the simulation results to support its feasibility. In our model, we break the dynamic symmetry by using an electric field to create a concentration difference of solute ions between the two liquid surfaces of a solution. The simulation results show that our ratchet model can induce a continuous net solvent flux. In that sense, all the positive work extracted from the heat bath can be available energy because it doesn't need to compensate the energy cost of the feedback controller. Our work makes it possible to construct an entirely mechanical molecule-rectifying system as Szilárd expected.