Electrical characterization of 26 × 26 ground reaction sensor array interfaced with two parallel electronic detection channels

pre-printThis paper presents the electrical characterization results of a 26 x 26 high-density ground reaction sensor array (HD-GRSA) interfaced with two parallel electronic detection channels. The system was developed for improving inertial measurement unit (IMU) positioning accuracy. The HD-GRSA is composed of 26 x 26 sensing nodes, which can measure dynamic ground force and shear strain associated with a ground locomotion gait. Each electronic detection channel consists of a front-end multiplexer that can sequentially connect individual sensing nodes from a 13 x 13 sub-array to a capacitance-to-voltage (C/V) converter followed by a 12-bit algorithmic ADC. The electronics were fabricated in a 0.35 μm CMOS process occupying an area of 7.7 mm2 for each channel while dissipating a DC power of 3 mW from a 3V supply. The HD-GRSA demonstrates the designed functionality achieving a gait ground velocity resolution of approximately 95 μmRMS/sec, limited by the electronic interference signals due to the long metal traces on the sensor array. Further performance improvement is expected by employing interference suppression techniques and better matching for critical wiring traces

MEMS-based hemispherical resonator gyroscopes

pre-printThis paper introduces a fabrication technique that uses planar MEMS micromachining processes to produce hemispherical resonating shells for gyroscopes. The hemispheres exhibit a quality factor in excess of 20,000 with resonant frequencies in the range of 20 kHz for the 4-node wineglass mode. The fabrication process enables production of almost perfect hemispheres (less than 1% asphericity near the pedestal) with an average surface roughness of 5nm. The high degree of sphericity contains the relative frequency mismatch Δf/f between the two degenerate modes to 0.02%. Simplicity of the fabrication process and the successful testing of the drive/sense mechanism in the resonator make it a good candidate for use as gyroscopes

Microfabrication of plasma nanotorch tips for localized etching and deposition

Journal ArticleAbstract-We present the microfabrication and initial testing of an AFM-tip like device, or nanotorch, that is capable of generating a very localized microplasma at its tip. The submicron region near its tip provides a unique manufacturing environment where new methods for controlled direct-write micro and nanofabrication can be tested. The device has been fabricated using both surface and bulk micromaching techniques. We demonstrated both localized submicrometer oxidazion patterning and imaging with the same device. Preliminary experiments have also been carried out demonstrating localized plasma etching of a polymer surface at atmospheric conditions with an AC voltage of 1000V

Personal navigation via high-resolution gait-corrected inertial measurement units

Journal ArticleAbstract-In this paper, a personal micronavigation system that uses high-resolution gait-corrected inertial measurement units is presented. The goal of this paper is to develop a navigation system that uses secondary inertial variables, such as velocity, to enable long-term precise navigation in the absence of Global Positioning System (GPS) and beacon signals. In this scheme, measured zerovelocity duration from the ground reaction sensors is used to reset the accumulated integration errors from accelerometers and gyroscopes in position calculation. With the described system, an average position error of 4 m is achieved at the end of half-hour walks

Electron Quantum Tunneling Sensors

Quantum tunneling sensors are typically ultra-sensitive devices which have been specifically designed to convert a stimulus into an electronic signal using the wondrous principles of quantum mechanical tunneling. In the early 1990s, William Kaiser developed one of the first micromachined quantum tunneling sensors as part of his work with the Nasa Jet Propulsion Laboratory. Since then, there have been scattered attempts at utilizing this phenomenon for the development of a variety of physical and chemical sensors. Although these devices demonstrate unique characteristics such as high sensitivity, the principle of quantum tunneling often acts as a double-edged sword and is responsible for certain drawbacks of this sensor family. In this review, we briefly explain the underlying working principles of quantum tunneling and how they are used to design miniaturized quantum tunneling sensors. We then proceed to describe an overview of the various attempts at developing such sensors. Next, we discuss their current need and recent resurgence. Finally, we describe various advantages and shortcomings of these sensors and end this review with an insight into the potential of this technology and prospects.Comment: arXiv admin note: substantial text overlap with arXiv:2006.1279

From chips to dust: the MEMS shatter secure chip

pre-printThis paper presents the implementation of a transience mechanism for silicon microchips via low-temperature post-processing steps that transform almost any electronic, optical or MEMS substrate chips into transient ones. Transience is achieved without any hazardous or explosive materials. Triggered chip transience is achieved by the incorporation of a distributed, thermally-activated expanding material on the chip backside. When heated at 160oC the expanding material produces massive chip cleavage mechanically shattering the chip into a heap of silicon dust

Characterization of electrical interferences for ground reaction sensor cluster

pre-printThis paper presents the characterization of electrical interferences for a high-resolution error-correcting biomechanical ground reaction sensor cluster (GRSC), developed for improving inertial measurement unit (IMU) position sensing accuracy. The GRSC is composed of 13 x 13 sensing nodes, which can measure dynamic ground forces, shear strains, and sole deformation associated with a ground locomotion gait. The integrated sensing electronics consist of a front-end multiplexer that can sequentially connect individual sensing nodes in a GRSC to a capacitance-to-voltage converter followed by an ADC, digital control unit, and driving circuitry to interrogate the GRSC. The characterization data shows that the single-ended (z-axis pressure) mode exhibits a large output interference due to the un-matched interconnect traces design, thus limiting sensing resolution to 8 bits. The differential mode (x/y-axes shear strain) shows a reduced interference effect, achieving a 10-bit resolution

Microfluidic device for triggered chip transience

pre-printThis paper presents the fabrication and testing of a microfluidic device for the triggered destruction (transience) of microchips. The device consists of a thin film array of sealed reservoirs patterned on a polymer film. Each reservoir encloses a corrosive chemical agent which upon release dissolves the surface of a microchip placed beneath. When transience is activated, an integrated micro-heater melts the bottom of the reservoirs thus releasing the chemical agent, which in a matter of minutes destroys key layers on the underlying electronic/sensor chip. Each reservoir consists of a 16 μm-tall cavity holding 1 μL/cm2 of 1000:1 BHF. The measured energy required to burst open a filled reservoir was ~35mJ/cm2 when the device rests on top of a glass substrate and ~100mJ/cm2 when the device rests on top of a 0.5 μm-layer of silicon dioxide on a 0.5 mm silicon wafer

Fabrication of localized plasma gold-tip nanoprobes with integrated microchannels for direct-write nanomanufacturing

pre-printWe present the microfabrication and characterization of an AFM-tip like device with integrated gas delivery microchannel for the generation of localized microplasmas. The device plasma is generated within a submicron region around its tip for direct-write micro and nanofabrication. The device is fabricated by forming a tall, sharp micromolded gold tip in a KOH etched inverted pyramid followed by thermo-compression bonding and consecutive tip transfer, microfluidic channel patterning and formation of supporting cantilever beam. The tall tip overcomes the height problems of previous designs. Preliminary experiments have been carried out demonstrating the generation of localized microplasma at atmospheric conditions with 1,000V AC stimulation. By mounting the device to a commercialized AFM station and operated in tapping mode, imaging with the same device has also been demonstrated

Precision curved micro hemispherical resonator shells fabricated by poached-egg micro-molding

pre-printThis paper presents a new technique for the fabrication of high resolution non-planar precision microshells for hemispherical resonating gyros via a poached-egg micromolding (PEM) method. In PEM, precision ball lenses are used as starting molds. Hemispherical shells are formed on the lenses using five major steps: (1) isotropic coating with sacrificial and shell layers, (2) stencil transfer of coated lenses to substrate, (3) shell top removal by anisotropic etching, (4) sacrificial layer etching and (5) release of the ball lens molds. Using PEM, we fabricated posted sputtered ultra-low-expansion glass hemispherical shells of 1 mm diameter and 1.2 μm thickness. The microshells have better than 120 ppm uniformity in thickness and less than ±0.125 μm deviation from a perfect sphere. The measured microshell resonant frequency at 100 mTorr was 17.32 kHz and the Q was ~ 20,000