We show that vibrating protrusions inside a microchannel are capable of steering fluid away from their relative orientation. This phenomenon is brought forth by symmetry-broken design of these protrusions. Vibration of these asymmetric protrusions is reciprocated in the streaming effect at the boundary layers of the channel thus inducing a net fluid flow. Additionally, we show that the flow direction is sensitive to switching acoustic frequencies. This acoustically-induced flow has the potential for transportation of nanoparticles as well as complex micro-structures. We hereby demonstrate this utility for contactless actuation of flagellar micro-agents as a foreground towards targeted drug release.

We report on the implementation of a confocal microscopy system based on a 2.9 THz quantum cascade laser source. Lateral and axial resolutions better than 70 mu m and 400 mu m, respectively, are achieved, with a large contrast enhancement compared to the non-confocal arrangement. The capability of resolving overlapping objects lying on different longitudinal planes is also clearly demonstrated. (C) 2012 Optical Society of Americ

In recent years, untethered microdevices have drawn significant attention due to their small size, weight and their ability to exert forces without the need for wires or tethers. Such microdevices are relevant to implantable biomedical devices, miniature robotics, minimally invasive surgery, and microelectromechanical systems. While devices using these actuators have been widely utilized in pick-and-place and biopsy applications, the forces exerted by these actuators have yet to be characterized and analyzed. Lack of precise force measurements and validated models impedes the clinical applicability and safety of such thin film microsurgical devices. Furthermore, present-day design of thin film microdevices for targeted applications requires an iterative trial-and-error process. In order to address these issues, we present a novel technique to measure the force output of thin film microactuators. Also, we develop and fabricate three designs of residual stress microactuators and use them to validate this technique, and establish a relationship between performance and design parameters. In particular, we find an inverse dependence of the thickness of the actuator and its force output, with 70 nm, 115 nm and 200 nm actuators exerting 7.8 μN, 4.7 μN, and 2.7 μN, respectively. Besides these findings, we anticipate that this microsystem measurement approach could be used for force measurements on alternate microactuators including shape memory, piezo and electromagnetic actuators.

We coupled linearly polarized and azimuthally polarized Terahertz quantum cascade lasers (QCLs) to the low-loss optical modes of hollow core waveguides having a sequence of different metallic or dielectric inner coatings. The latter waveguides have been specifically designed to force the propagation of a dominant optical mode once the thickness (d) of the inner dielectric coating is properly chosen. Our results demonstrate that both the TE01 and the TE11 modes can be easily converted to a hybrid one when d > 6 mu m allowing the propagation of THz QCL beams with transmission losses as low as 1.5 dB/m, bending losses < 1.1 dB and reasonably high coupling efficiencies (87%)

We present GaAs/AlGaAs double quantum well devices that can operate as both electron-hole (e-h) and hole-hole (h-h) bilayers, with separating barriers as narrow as 5 nm or 7.5 nm. With such narrow barriers, in the h-h configuration, we observe signs of magnetic-field-induced exciton condensation in the quantum Hall bilayer regime. In the same devices, we can study the zero-magnetic-field e-h and h-h bilayer states using Coulomb drag. Very strong e-h Coulomb drag resistivity (up to 10% of the single layer resistivity) is observed at liquid helium temperatures, but no definite signs of exciton condensation are seen in this case. Self-consistent calculations of the electron and hole wavefunctions show this might be because the average interlayer separation is larger in the e-h case than the h-h case.