Apparatus, devices, and methods for shearing nucleic acids are provided. In one exemplary embodiment the device is a disposable nucleic acid shearing cartridge. The cartridge includes two reservoirs, an orifice structure disposed therebetween, and a fluid driver. The reservoirs are in fluid communication with each other by way of the orifice structure, and the fluid driver cycles a sample between the two reservoirs. By passing a sample from one reservoir to the next, through the orifice structure, an orifice located in the orifice structure can shear the sample to a desired length. The sheared sample can then be used, for example, in a sequencing device. Apparatuses for cycling samples in the cartridge, and methods and kits for shearing nucleic acids, are also disclosed.