Frank M. Yaul

Lateral-line inspired sensor arrays for navigation and object identification

Found to affect numerous aspects of behavior, including maneuvering in complex fluid environments with poor visibility, the lateral line is a critical component of fish sensory systems. This sensory organ could fill the gap left by sonar and vision systems in turbid, cluttered environments; it has no analog in modern ocean vehicles, despite its utility and ubiquity in nature. A linear array of pressure sensors is used along with analytic models of the fluid in order to emulate the lateral line and characterize its object-tracking and shape recognition capabilities. Position, shape, and size of various objects in both passive and active sensing schemes are thus determined. The authors find that tracking a moving cylinder can be effectively achieved via a particle filter, based on pressure information. The authors are also able to reliably distinguish between cylinders of different cross section, using principal component analysis, as well as identify the critical flow signature information that leads to the shape identification. The authors employ pressure measurements on an artificial fish and an unscented Kalman filter in a second application in order to successfully identify the shape of an arbitrary static cylinder. The authors conclude that, based on the experiments, a linear pressure sensor array for identifying small objects should have a sensor-to-sensor spacing of less than 0.03 (relative to the length of the sensing body) and resolve pressure differences of at least 10 Pa. These criteria employ conductive polymer technologies to form a flexible array of small pressure sensors in order to be used in the development of an artificial lateral line adaptable to the curved hull of an underwater vehicle.

11.3 A 10b 0.6nW SAR ADC with data-dependent energy savings using LSB-first successive approximation

ADCs used in medical and industrial monitoring often transduce signals with short bursts of high activity followed by long idle periods. Examples include biopotential, sound, and accelerometer waveforms. Current approaches to save energy during periods of low signal activity include variable resolution and sample rate systems [1], asynchronous level-crossing ADCs [2], and ADCs that bypass bitcycles when the signal is within a predefined small window [3]. This work presents a signal-activity-based power-saving algorithm called LSB-first successive approximation (SA) that maintains a constant sample rate and resolution, scales logarithmically with signal activity, and does not inherently suffer from slope overload.

A 10 bit SAR ADC With Data-Dependent Energy Reduction Using LSB-First Successive Approximation

This paper presents a successive approximation (SA) algorithm called LSB-first SA and a corresponding 10 bit ADC implementation. The energy per conversion and number of bitcycles per conversion used by this algorithm both scale logarithmically with the activity of the input signal, such that an N-bit conversion uses between 2 and 2N+1 bitcycles, compared to N for conventional binary SA. This algorithm reduces ADC power consumption when sampling signals with low mean activity. The ADC is implemented in a 0.18 μm CMOS process. With a 0.6 V supply, the maximum sample rate, leakage power, and ENOB are 16 kHz, 0.58 nW, and 9.73 b, averaged over 10 test chips. The DNL and INL are bounded at 0.09 and 0.22 LSBs. Given a DC input, the ADC achieves its best-case FoM of 3.5 fJ/conversion-step. Given a fullscale Nyquist sinusoid input, the ADC has its worst-case FoM of 20 fJ/conversion-step. The supply voltage can be increased to 1.0 V to reach a sample rate of 450 kHz, or decreased to 0.5 V to achieve a 2.9-17 fJ/conversion-step FoM range.

Small-Area, Resistive Volatile Organic Compound (VOC) Sensors Using Metal–Polymer Hybrid Film Based on Oxidative Chemical Vapor Deposition (oCVD)

We report a novel room temperature methanol sensor comprised of gold nanoparticles covalently attached to the surface of conducting copolymer films. The copolymer films are synthesized by oxidative chemical vapor deposition (oCVD), allowing substrate-independent deposition, good polymer conductivity and stability. Two different oCVD copolymers are examined: poly(3,4-ethylenedioxythiophene-co-thiophene-3-aceticacid)[poly(EDOT-co-TAA)] and poly(3,4-ehylenedioxythiophene-co-thiophene-3-ethanol)[poly(EDOT-co-3-TE)]. Covalent attachment of gold nanoparticles to the functional groups of the oCVD films results in a hybrid system with efficient sensing response to methanol. The response of the poly(EDOT-co-TAA)/Au devices is found to be superior to that of the other copolymer, confirming the importance of the linker molecules (4-aminothiophenol) in the sensing behavior. Selectivity of the sensor to methanol over n-pentane, acetone, and toluene is demonstrated. Direct fabrication on a printed circuit board (PCB) is achieved, resulting in an improved electrical contact of the organic resistor to the metal circuitry and thus enhanced sensing properties. The simplicity and low fabrication cost of the resistive element, mild working temperature, together with its compatibility with PCB substrates pave the way for its straightforward integration into electronic devices, such as wireless sensor networks.

5.4 A sub-µW 36nV/√Hz chopper amplifier for sensors using a noise-efficient inverter-based 0.2V-supply input stage

In low-bandwidth, low-noise applications of wireless sensor nodes, the sensor front-end amplifier presents a power-consumption bottleneck since its current draw is noise-limited and cannot be scaled with the low data-rate, as is possible with the DSP and RF blocks. EEG monitoring is one application where designers have targeted sub-microvolt input-referred noise over a signal band of 0.5 to 100Hz [1]. Prior work to improve the energy-efficiency of low-noise instrumentation amplifiers (LNIAs) for sensors includes chopper IAs [1,2], inverter-based LNAs [3], current-reuse through amplifier stacking [4], and low-supply-voltage amplifier design reaching 0.45V [5].

Micro-contact printed MEMS

We report a new method for fabricating thin (140 nm thick) suspended metal films in MEMS. Our MEMS fabrication process employs micro-contact printing. It avoids the use of solvents and etchants, obviating the need for deep reactive-ion etching and other harsh chemical treatments. Solvent absence during fabrication also avoids the deleterious effects of MEMS stiction that can result during wet processing. Elevated temperature processing is also avoided to enable MEMS fabrication on flexible polymeric substrates. Thin films up to 0.78 mm2 in area are fabricated and the deflection of 25 µm diameter films is demonstrated. These films can be utilized in pressure sensors, microphones, deformable mirrors, tunable optical cavities, and large-area arrays of MEMS sensors.

A flexible underwater pressure sensor array using a conductive elastomer strain gauge

This paper presents a flexible underwater pressure sensor array which achieves a 1.5 pascal pressure resolution using a 16-bit analog/digital converter. Each sensor consists of a polydimethysiloxane (PDMS) diaphragm and a resistive strain gauge made of a conductive carbon black-PDMS composite. A functional linear array of four sensors with a 15 mm center-to-center spacing is demonstrated, and the dynamic response of the sensors is characterized and modeled.