No abstract

Vertically aligned CNTs exhibit 100× and 170× higher capacitance when coated with ALD RuOx and after further electrochemical oxidation, respectively.

Polymeric microneedles fabricated by microinjection molding techniques have been demonstrated using Topas Ò COC as the molding plastic material. Open-channel microneedles with cross-sectional area of 100 lm · 100 lm were designed and fabricated on top of a shank of 4.7 mm in length, 0.6 mm in width, and 0.5 mm in depth. The tip of the microneedle has a round shape with a radius of 125 lm as limited by the drill used in fabricating the mold insert. The injection molding parameters including clamping force, shot size, injection velocity, packing pressure, and temperature were characterized in order to achieve best reproducibility. Experimentally, a fabricated microneedle was successfully injected into a chicken leg and a beef liver freshly bought from a local supermarket and about 0.04 lL of liquid was drawn from these tissues immediately. This new technology allows mass production of microneedles at a low cost for potential biomedical applications.

No abstract

No abstract

We have successfully demonstrated highly responsive, curved piezoelectric micromachined ultrasonic transducers (pMUTs) based on a CMOS-compatible fabrication process using AlN (aluminum nitride) as the transduction material. Micro fabrication techniques have been used to control the radius of curvature of working diaphragms from 400~2000 μm and theoretical analysis have been developed for the optimal dimensions of the transducers to boost the electromechanical coupling and acoustic pressure. A prototype device made of a 2µm-thick AlN on a curved diaphragm with a nominal size of 140µm in diameter and a radius of curvature of 1065µm has been fabricated. The measured resonant frequency is 2.19MHz and DC response is 1.1nm/V, which is 50X higher than that of a planar device with the same nominal diameter. As such, this new class of curved pMUTs could dramatically enhance the responses of the state-of-art, planar pMUTs with high electromechanical coupling for various ultrasonic transduction applications, such as gesture recognition and medical imaging.

No abstract

In this work, the deflection equation of a piezoelectrically-driven micromachined ultrasonic transducer (PMUT) is analytically determined using a Green's function approach. With the Green's function solution technique, the deflection of a circular plate with an arbitrary circular/ring electrode geometry is explicitly solved for axisymmetric vibration modes. For a PMUT with one center electrode covering ≈60% of the plate radius, the Green's function solution compares well with existing piece-wise and energy-based solutions with errors of less than 1%. The Green's function solution is also simpler than them requiring no numerical integration, and applies to any number of axisymmetric electrode geometries. Experimentally measured static deflection data collected from a fabricated piezoelectric micro ultrasonic transducer (PMUT) is further used to validate the Green's function model analysis. The center deflection and deflection profile data agree well with the Green's function solution over a range of applied bias voltages (5 to 21 V) with the average error between the experimental and Green's function data less than 9%.