Showing papers by "Edward Hæggström published in 2013"

Algorithm for automatic analysis of electro-oculographic data.

Abstract: Large amounts of electro-oculographic (EOG) data, recorded during electroencephalographic (EEG) measurements, go underutilized. We present an automatic, auto-calibrating algorithm that allows efficient analysis of such data sets. The auto-calibration is based on automatic threshold value estimation. Amplitude threshold values for saccades and blinks are determined based on features in the recorded signal. The performance of the developed algorithm was tested by analyzing 4854 saccades and 213 blinks recorded in two different conditions: a task where the eye movements were controlled (saccade task) and a task with free viewing (multitask). The results were compared with results from a video-oculography (VOG) device and manually scored blinks. The algorithm achieved 93% detection sensitivity for blinks with 4% false positive rate. The detection sensitivity for horizontal saccades was between 98% and 100%, and for oblique saccades between 95% and 100%. The classification sensitivity for horizontal and large oblique saccades (10 deg) was larger than 89%, and for vertical saccades larger than 82%. The duration and peak velocities of the detected horizontal saccades were similar to those in the literature. In the multitask measurement the detection sensitivity for saccades was 97% with a 6% false positive rate. The developed algorithm enables reliable analysis of EOG data recorded both during EEG and as a separate metrics.

One kilometer (1 km) electric solar wind sail tether produced automatically.

Abstract: We produced a 1 km continuous piece of multifilament electric solar wind sail tether of μm-diameter aluminum wires using a custom made automatic tether factory. The tether comprising 90 704 bonds between 25 and 50 μm diameter wires is reeled onto a metal reel. The total mass of 1 km tether is 10 g. We reached a production rate of 70 m/24 h and a quality level of 1‰ loose bonds and 2‰ rebonded ones. We thus demonstrated that production of long electric solar wind sail tethers is possible and practical.

An optoacoustic point source for acoustic scale model measurements

Abstract: A massless acoustic source is proposed for scale model work. This source is generated by focusing a pulsed laser beam to rapidly heat the air at the focal point. This produces an expanding small plasma ball which generates a sonic impulse that may be used as an acoustic point source. Repeatability, frequency response, and directivity of the source were measured to show that it can serve as a massless point source. The impulse response of a rectangular space was determined using this type of source. A good match was found between the predicted and the measured impulse responses of the space.

Phase-delayed laser diode array allows ultrasonic guided wave mode selection and tuning

Abstract: Selecting and tuning modes are useful in ultrasonic guided wave non-destructive testing (NDT) since certain modes at various center frequencies are sensitive to specific types of defects. Ideally one should be able to select both the mode and the center frequency of the launched waves. We demonstrated that an affordable laser diode array can selectively launch either the S0 or A0 ultrasonic wave mode at a chosen center frequency into a polymer plate. A fiber-coupled diode array (4 elements) illuminated a 2 mm thick acrylic plate. A predetermined time delay matching the selected mode and frequency was employed between the output of the elements. The generated ultrasound was detected by a 215 kHz piezo receiver. Our results imply that this array permits non-contacting guided wave ultrasonic NDT. The solution is small, affordable, and robust in comparison to conventional pulsed lasers. In addition, it does not require experienced operators.

Stroboscopic scanning white light interferometry at 2.7 MHz with 1.6 µm coherence length using a non-phosphor LED source

Abstract: Stroboscopic scanning white light interferometry (SSWLI) allows precise three dimensional (3D) measurements of oscillating samples. Commercial SSWLI devices feature limited pulsing frequency. To address this issue we built a 400-620 nm wideband 150 mW light source whose 1.6 µm wide interferogram is without side peaks. The source combines a non-phosphor white LED with a cyan LED. We measured a calibration artifact with 10 nm precision and obtained 40 nm precision when measuring the 3D profile of a capacitive micromachined ultrasonic transducer membrane operating at 2.72 MHz. This source is compatible with solid state technology.

Photo-acoustic phase-delayed excitation of guided waves in coated bone phantoms

Abstract: Photo-acoustic skeletal quantitative ultrasound enables assessment of the fundamental flexural guided wave (FFGW) propagating in bone. This mode, consistent with the F(1,1) tube mode can now be measured through a coating of soft tissue. Interference due to ultrasound propagation in the soft tissue surrounding the bone is reduced by using phase-delayed ultrasound excitation. Photo-acoustic phase-delayed excitation was done on five axisymmetric bone phantoms (1-5 mm wall thickness), coated by a 5 mm thick soft-tissue mimicking layer. A fiber head comprising a linear array of four optical fibers (400 μm diameter), illuminated by pulsed laser diodes (905 nm wavelength) generated ultrasound. This sound was received by a small (10 mm diameter) custom-made piezo transducer from the top surface of the coating. Tuning the phase delay allowed selection of the excited mode(s). FFGW was detected in the 20-40 kHz band when the power ratio between FFGW and interference was tuned to a local maximum. This tuning removed interference and improved SNR of the FFGW mode by >10 dB. Fitting the theoretical FLC(1,1) mode of a liquid-coated (LC) tube to the measured FFGW phase-velocity provided accurate (11% ± 7% rms deviation) estimate for the cortical thickness. These results suggest that photo-acoustic phase-delayed excitation may enable in vivo assessment of cortical thickness based on FFGW.

Nondestructive Inspection of Buried Channels and Cavities in Silicon

Abstract: Microelectromechanical systems and microfluidic devices feature buried channels, cavities, and other embedded microstructures. These features are usually examined by breaking the wafer and by imaging the revealed cross section. We propose a nondestructive technique to evaluate the shape and surface quality of buried microchannels with submicrometer resolution. The technique relies on infrared light interferometry. We employed the technique to nondestructively examine channels and cavities through a silicon roof. With the proposed technique, we can quantitatively examine the size and shape of microchannels that are hidden to visible light.

Through-Silicon Stroboscopic Characterization of an Oscillating MEMS Thermal Actuator Using Supercontinuum Interferometry

Abstract: We measured the surface profile of the hidden face of a thermally actuated oscillating 4-μm-thick silicon microelectromechanical system (MEMS) bridge. To do this, we employed a stroboscopically synchronized supercontinuum light source incorporated into a scanning low-coherence interferometer. The instrument exploited the near-infrared part (1.1-1.7 μm) of the emitted spectrum and a camera sensitive to near infrared. The MEMS bridge was driven with 6.8-V sinusoidal voltage at 10 Hz, which resulted in oscillation amplitudes of 1.50 ± 0.07 μm and 1.35 ± 0.07 μm for the top and bottom surfaces, respectively. We believe this technique opens up new possibilities for validating simulation effort as well as for qualifying new device designs.

High-speed stroboscopic imaging with frequency-doubled supercontinuum.

Abstract: We present a supercontinuum (SC) light source designed for stroboscopic white light interferometry. The compact, cost-effective SC source is built from off-the-shelf optical components and operates both in the visible and near-IR at arbitrary repetition rates in the 10 kHz–1 MHz frequency range. We estimate that our source allows performing dynamic white-light interferometric characterization of rapidly oscillating objects up to several tens of megahertz. Its current potential is demonstrated by capturing the movement of a microelectromechanical system oscillating at 2.16 MHz with sub-100 nm accuracy.

Quasidynamic calibration of stroboscopic scanning white light interferometer with a transfer standard

Abstract: A stroboscopic scanning white light interferometer (SSWLI) can characterize both static features and motion in micro(nano)electromechanical system devices. SSWLI measurement results should be linked to the meter definition to be comparable and unambiguous. This traceability is achieved by careful error characterization and calibration of the interferometer. The main challenge in vertical scale calibration is to have a reference device with reproducible out-of-plane movement. A piezo-scanned flexure guided stage with capacitive sensor feedback was attached to a mirror and an Invar steel holder with a reference plane—forming a transfer standard that was calibrated by laser interferometry with 2.3 nm uncertainty. The moving mirror vertical position was then measured with the SSWLI, relative to the reference plane, between successive mirror position steppings. A light-emitting diode pulsed at 100 Hz with 0.5% duty cycle synchronized to the CCD camera and a halogen light source were used. Inside the scanned 14 μm range, the measured SSWLI scale amplification coefficient error was 0.12% with 4.5 nm repeatability of the steps. For SWLI measurements using a halogen lamp, the corresponding results were 0.05% and 6.7 nm. The presented methodology should permit accurate traceable calibration of the vertical scale of any SWLI.

MHz ultrasonic drive-in: Localized drug delivery for osteoarthritis therapy

Abstract: Osteoarthritis (OA) is a significant musculoskeletal disease with no cure. Current drug delivery techniques feature poor spatial localization (systemic delivery or injection into the synovial capsule). We previously used kHz high-intensity ultrasound to deliver micro- and nano-particles into articular cartilage (AC). Here we investigated whether MHz ultrasound can deliver particles into AC. Using high-intensity focused ultrasound (HIFU) we drove agents into 45% depth of the AC thickness. In addition, laser-induced shock waves showed drive-in effect. Our results demonstrate that MHz ultrasound can locally administer agents into AC. The technique could potentially be used for localized OA drug therapy.

Solid state switch for gigahertz coded signal ultrasound microscopy

Abstract: Presented is a solution for ultrasonic microscopy that permits using coded gigahertz signals. It features a high frequency arbitrary signal source (upconverted quadrature I-Q modulation), a solid state switch, and a preamplifier. Commercial 3 GHz solid state switches that handle 15 Vpp signals and a 0.01–1.2 GHz low noise preamplifier (3.3 dB noise figure) were used, all developed for wireless networking. The device was validated with a custom built ultrasound immersion microscope by imaging a 5 µm-tall MEMS step structure using 100–300 MHz, 3 µs, 10.5 Vpp linear chirp excitation.

GHz ultrasonics with arbitrary code excitation

Abstract: Recently we developed a high frequency coded signal ultrasound microscope based on quadrature modulation [1, 2] The device allowed pulse-echo operation at 300 MHz, however, local oscillator crosstalk reduced the SNR of pulse compression To achieve GHz-range operation we present an improved design with new RF-components The new design improved SNR by 16 dB compared to [2] We also investigated the use of a dual-band chirp to further reduce the local oscillator interference We successfully tested the device with a GHz ultrasound transducer in 09-11 GHz band using an arbitrary TX code This achievement is a first step towards bringing the advantages of coded excitation into GHz ultrasound microscopy

Ultrasonic Determination of Porosity in Homogeneous Ceramic Samples

Abstract: An ultrasonic method was tested to rapidly determine the porosity in custom made ceramic samples. The samples with porosities between 4 and 33% were of identical composition. The porosity estimates by ultrasonic method were validated against those obtained by helium and air pycnometry as well as with Archimedean method. The ultrasonic measurements can be performed rapidly (less than a minute) but they require a well prepared sample.

Ultrasonic estimate of the modulus of rupture and quantification of the frequency dependent dynamic modulus in Norway Spruce

Abstract: Ultrasonic measurements allow non-destructive evaluation of mechanical properties of wood. However, it is unclear how these ultrasonically determined properties relate to comparable values obtained by traditional mechanical experiments, e.g., three point bending performed at different probing frequencies. In addition, although a link between the modulus of rupture (MOR) and the modulus of elasticity (MOE) obtained with static methods is established, little research exists on the correlation between the ultrasonically determined dynamic elastic modulus and MOR. Therefore, we set out to link the modulus values obtained by three-point bending to those obtained by ultrasonic measurements at different frequencies. We compared the modalities using a fractional derivative model that theoretically predicts a frequency dependency of the dynamic elastic modulus. We determined MOE and MOR in 102 Norway Spruce samples (340 to 510 kg/m3 density) by three-point bending followed by ultrasonic through-transmission measurements that quantified the dynamic modulus at 500 kHz, 4 MHz, and 8 MHz. This is the first report on such a frequency series for Norway Spruce. Our results provide a conversion factor that permits comparing ultrasonically and statically measured MOE values. Depending on the ultrasonic frequency, correlations ranging from 0.3 to 0.53 between the ultrasonic dynamic modulus and MOR were found.

Detecting defects in adhesion between a metal hemisphere and a polymer base

Abstract: Detecting localized defects in adhesion on a spherical shell is challenging, especially if one has access only to its rim. Our group previously quantified the spatial average of the adhesion between a metal hemisphere and a polymer base [1]. Here we report on progress towards determining the presence of localized defects, their position, size, and strength. Tests were performed on a 5 cm diameter metal hemisphere attached to a UHMWPE (Polyethylene, PE RCH 1000 D150×2000 Etralene) base. Defects in adhesion were generated by machining hexagonal holes (5 to 17.5 mm) into the polymer base prior to fixing by adhesive. These known areas without adhesion were remotely characterized with a guided ultrasonic wave (Lamb quasi-modes) generated by a Nd:YAG (1064 nm, 8 ns pulse duration) pulse from one rim of the shell and detected with a laser Doppler vibrometer. We detected the presence and position of the defects.

Space tether produced to strength specification

Abstract: A non-contact method to determine the quality of an ultrasonic weld was developed for wire-to-wire bonding purposes. Relative wire movement during the bonding process was monitored with a laser-doppler-vibrometer. This movement provides information about the bond development. Such information permits predicting the final quality of the bond. Signals from N=5000 bonds were analyzed to find tell tale characteristics that predict the final strength of the bond. A bond that eventually will end up failed (un-attached) can be recognized as early as 2 ms into the bonding process. A distinction between poor quality (maximum sustainable pull-force below 8 g) and good quality (pull-force above 10 g) bonds can be recognized within 6 ms from the bonding start. A real-time feedback system was implemented to reduce the uncertainty in final bond quality and to actively augment the quality during the bonding process. The purpose of this study was to confirm that real-time quality assurance (produce to specification) is feasible in wire-to-wire bonding. This work is part of our efforts towards the produce to specification concept in the ESAIL programme.

Determining the quality of space tether in a nondestructive manner

Abstract: We propose a nondestructive method to determine the quality of each bond in an electric solar wind sail (E-sail) tether. The method is verified by a method similar to the standard destructive pull test [1]. The setup that we built for the proposed in-line tether quality measurement comprises a custom-built ultrasonic bonder, a laser doppler vibrometer, an ultrasonic generator, contact resistance measurement electronics, and a laser-ultrasonic device. During the bonding process the setup continuously measures voltage and current driving the ultrasonic transducer, the bonding lower wedge displacement, the contact resistance of the bond interface and a laser-induced high frequency pulse transmission through the bond interface. The post-production analysis results are correlated with the destructive bond pull test results to identify a target signal path. Staying on this path should ensure strong bonds. This work is part of our efforts towards the produce to specification concept in the ESAIL programme.

Ultrasonic damage assessment of articular cartilage for ultrasonic drug delivery

Abstract: Osteoarthritis (OA) is a common musculoskeletal disease. There are drug therapies under development, but no localized way to transfer drugs into articular cartilage (AC). Previously we showed that 20 kHz high intensity ultrasound (HIU) can deliver micro- and nano-particles into AC [1]. However, at low frequencies, cavitation may occur. Our hypothesis is that 20 MHz ultrasound pulse-echo can be used to track changes in ultrasound reflection from AC during HIU. Here we tested the feasibility of this approach for characterizing cavitation-related damage. We observed that the relative decrease in mean surface reflection coefficient at 15, 20 and 25 MHz were -40.9 +/- 7.9 %, -53.4 +/- 12.0 % and -61.1 +/- 7.1 %, respectively, during a 5-minute HIU exposure. Frequencies above 16 MHz were the most sensitive to changes induced by HIU in both samples. We propose that the change resulted from cavitation-related cratering of the AC surface and exposure of AC tissue with lower collagen content. In conclusion, the acoustic reflection coefficient of the AC surface could be a sensitive parameter to estimate damage in the AC surface during HIU exposure.

Anisotropy of longitudinal and shear wave velocities in rocks under controlled pressure

Abstract: Reliable interpretation of seismic surveys and borehole loggings requires that the seismic velocities and anisotropies of the bedrock are taken into account. There will be discrepancies in estimated reflector locations if one assumes isotropic velocity. Moreover, improved accuracy in determining reflector locations reduces drilling efforts in ore exploration. Our custom-built ultrasonic triaxial anvil setup permits measuring longitudinal (Vp) (1 MHz center frequency) and shear wave (Vs) (1.1 MHz center frequency with 0° and 90° polarization options) sound velocities in cubic rock samples (sides ~25 mm) under crustal-pressures up to 300 MPa in three directions (X, Y, and Z) simultaneously. Our results of eleven Precambrian rock samples from the FIRE-reflection profile in Central Finland show 3408-7250 m/s (Vs) and 2460-4140 m/s (Vp). The calculated velocity anisotropy values of these samples vary from 22% to 2% with applied pressure (up to 102 MPa).

Traceable characterization of cMUT membrane motion

Abstract: Silicon micromachining permits tailoring, for optimal device performance, the active membranes of capacitive micromachined ultrasound transducers (cMUTs). The membrane motion determines much of the transducer performance. In a thrust towards traceable characterization of cMUT membrane movement we compared a full field 3D imaging technique with a raster scan laser doppler vibrometry (LDV) technique. The 3D profiles of a moving cMUT membrane oscillating at 2.72 MHz were measured using stroboscopic scanning white light interferometry (SSWLI). In SSWLI pulsed illumination is synchronized with the sample oscillation. This method can characterize both in-plane and out-of-plane sample motion. A broadband, rapidly switchable and stable, light source is essential for the technique. Such sources can't be bought.