Jeremy A. Levitan

Fast ac electro-osmotic micropumps with nonplanar electrodes

This letter demonstrates dramatic improvements in flow rate and frequency range over conventional planar ac electro-osmotic (ACEO) pumps by exploiting three-dimensional (3D) stepped electrodes. A 3D ACEO pump was fabricated by electroplating steps on a symmetric electrode array and tested against a state-of-the-art asymmetric planar ACEO pump in a microfluidic loop. For all frequencies (0.1–100kHz), the 3D pump had a faster flow rate, in some cases by an order of magnitude. Their experimental results suggest that, after some optimization, mm/s velocities will be attainable with alternating battery voltages, which presents an exciting opportunity for microfluidics.

High-resolution micromachined interferometric accelerometer

We demonstrate a promising type of microfabricated accelerometer that is based on the optical interferometer. The interferometer consists of surface-micromachined interdigital fingers that are alternately attached to a proof mass and support substrate. Illuminating the fingers with coherent light generates a series of diffracted optical beams. Subangstrom displacements between the proof mass and frame are detected by measuring the intensity of a diffracted beam. The structure is fabricated with a two-mask silicon process and detected with a standard laser diode and photodetector. We estimate that the minimum detectable acceleration is six orders of magnitude below the acceleration of gravity, i.e., 2 μg/Hz in a 1 Hz bandwidth centered at 650 Hz.

Application of Smart Materials to Wireless ID Tags and Remote Sensors

Material structures having an electromagnetic or magnetomechanical resonance can be excited or detected remotely using an antenna. Incorporating smart materials into such structures provides new opportunities to encode ID and sensor information in the electromagnetic signature of the “tag.” In this way, it is possible to create tags which not only have a unique ID but which can also respond to local changes in their environment (e. g. force, temperature, light, etc.). This principle forms the basis for a low-cost wireless ID and wireless sensor technology which has many potential applications in manufacturing, inventory control, security, surveillance, and new human-computer interfaces. As a means of illustrating this concept, two simple examples are given: a force sensor incorporating a piezoelectric polymer and a relative position sensor which incorporates a magnetoelastic amorphous metal ribbon.