A chain tensioner includes a shoe including a first spring-receiving slot and a second spring-receiving slot. In one embodiment, a method of manufacturing a droplet actuator for conducting droplet operations includes positioning a dielectric material between a first metal layer configured to include an electrode and a second metal layer configured to include an interconnect pad. The toner prevents image contamination caused by dispersion of waxes or colorants onto the surface of the outer layer of toner particles are prevented. Once the polyurethane is cured, the tabs are machined off leaving a striking surface on the face insert that is flush with the front face of the body. A hydraulic pump and reservoir provide hydraulic power to the hydraulic motor and actuators.