A dual fluid cartridge which reduces fluid waste while minimally increasing back pressure is disclosed. One beam is shifted with respect to the other beam, with the aid of a modulating device, in terms of the beam’s light phase or light frequency, and passes through a delay line. By avoiding wavelengths associated with strong absorption in the underlying material, creating optical traps with a continuous-wave laser, optimizing the efficiency of individual traps, and trapping extended samples at multiple points, the rate of deleterious nonlinear optical processes can be minimized. An electrostatic MEMS actuator can be used to effect movement of the autofocus mechanism, zoom mechanism, andor image stabilization mechanism. Structures such as walls may be constructed on the foundations prior to dropping the foundations and bracing members may be used to prevent deflection of the walls. The four roller assembly includes at least one rotation encoder, which provides an output to the electronic controller about the length of a tree.