Generation MEMS Research Articles

Nanotwinned metal MEMS films with unprecedented strength and stability.

Silicon-based microelectromechanical systems (MEMS) sensors have become ubiquitous in consumer-based products, but realization of an interconnected network of MEMS devices that allows components to be remotely monitored and controlled, a concept often described as the "Internet of Things," will require a suite of MEMS materials and properties that are not currently available. We report on the synthesis of metallic nickel-molybdenum-tungsten films with direct current sputter deposition, which results in fully dense crystallographically textured films that are filled with nanotwins. These films exhibit linear elastic mechanical behavior and tensile strengths exceeding 3 GPa, which is unprecedented for materials that are compatible with wafer-level device fabrication processes. The ultrahigh strength is attributed to a combination of solid solution strengthening and the presence of dense nanotwins. These films also have excellent thermal and mechanical stability, high density, and electrical properties that are attractive for next-generation metal MEMS applications.

Optical MEMs transducers with enhanced efficiency and sensitivity

We introduce a highly sensitive laser ultrasonic detection MEMs transducer and an efficient laser ultrasound generation MEMs transducer. The detection transducer consists of a series of cantilevers with the same dimensions; any two cantilevers next to each other are separated by a solid with the same width as finger's. When ultrasound is incident upon this transducer, as long as there is a vibration component perpendicular to each finger's top surface and with a frequency the same as the finger's first resonance in the ultrasound, each finger will resonate upon the ultrasound. The moving fingers and the still solid separations form an optical phase grating, and therefore the ultrasound can be readout by a detection laser remotely. Because the ultrasound amplitude is amplified many times by the transducer's resonance before detection, the sensitivity of this transducer is much higher than that of traditional transducers. The generation transducer consists of a micro-disk seated upon a micro-stem. When a suitably focused laser pulse illuminated on the center of the disk, a certain order of flapping motion of the disk is mainly actuated, while other orders are just slightly, or not excited. This flapping motion couples a very narrow bandwidth of longitudinal wave propagating along the axis of the stem and into a sample. Because all absorbed optical energy is concentrated into this narrowband ultrasound, its amplitude is much higher than that of normal thermoelastic generation. It is possible to use these MEMs generation and detection transducers to form a simple but highly efficient laser ultrasound generation and detection system in the near future.

Study of Polymeric Microneedle Arrays for Drug Delivery

ABSTRACTTwo-photon polymerization (2PP) is a novel technology for the fabrication of complex three-dimensional (3D) microstructures. The number of applications employing this technology is rapidly increasing, and includes the fabrication of three-dimensional photonic crystals [1-4], medical devices, and scaffolds for tissue engineering [5, 6]. We have used 2PP to fabricate microneedle arrays with various geometries. These devices provide a unique approach for transdermal delivery of nucleic acid- and protein-based pharmacologic agents. Many of issues associated with conventional intravenous drug administration, including pain to the patient, trauma at the injection site, and difficulty in providing sustained release of a pharmacological agent, may be eliminated by applying the microneedles. The effect of microneedle geometry (e.g., tip sharpness and aspect ratio) on skin penetration was examined. Our results indicate that microneedles created using 2PP technique are suitable for in vivo use, and integration with next generation MEMS- and NEMS-based drug delivery devices.

A second generation MEMS surface fence sensor for high resolution wall shear stress measurement

The measurement of the wall shear stress in fluid mechanics has important implications for the investigation of turbulent flow phenomena. An advanced version of the MEMS silicon surface fence sensor that measures this stress is presented herein. This sensor consists of a cantilever structure with a length of 5 mm, a height of 315 μm, and a thickness of 10 μm. Fluid flowing towards this structure causes it to bend. The resulting bending stress in the cantilever is measured with four piezoresistors, and this stress is correlated to the wall shear stress. The offset voltage has been reduced significantly. The sensor operates over a range of approximately −1 to +1 N/m 2 with a resolution of 10 mN/m 2.