The real-time monitoring of aerosols is important for protecting human health and the environment. The small size of microchannels and their potential for integration with sensing technologies suggest them as a promising tool for the next generation of aerosol sensors. To that end, we present a novel microfluidics-based system for the size-separation of aerosols using the centrifugal force exerted on each particle as it travels around a curve. We demonstrate with simulations and experiments the separation by size of mixtures of aerosolized microspheres with diameters ranging from 0.2-3.2 µm. With bidisperse particle sizes in a single-outlet channel, a separation efficiency is defined to quantify how much of each of the two sizes of particles are located in distinct regions of the channel; the separation of mixtures at up to 80% separation efficiency is demonstrated. Particles are also separated into two or three outlets, each containing a different distribution of particles by size. Both experimental particle position and separation efficiency results match well with the simulations.