Tactile feedback display with spatial and temporal resolutions.

We report the electronic recording of the touch contact and pressure using an active matrix pressure sensor array made of transparent zinc oxide thin-film transistors and tactile feedback display using an array of diaphragm actuators made of an interpenetrating polymer elastomer network. Digital replay, editing and manipulation of the recorded touch events were demonstrated with both spatial and temporal resolutions. Analog reproduction of the force is also shown possible using the polymer actuators, despite of the high driving voltage. The ability to record, store, edit, and replay touch information adds an additional dimension to digital technologies and extends the capabilities of modern information exchange with the potential to revolutionize physical learning, social networking, e-commerce, robotics, gaming, medical and military applications

High-speed imaging in fluids

High-speed imaging is in popular demand for a broad range of experiments in fluids. It allows for a detailed visualization of the event under study by acquiring a series of image frames captured at high temporal and spatial resolution. This review covers high-speed imaging basics, by defining criteria for high-speed imaging experiments in fluids and to give rule-of-thumbs for a series of cases. It also considers stroboscopic imaging, triggering and illumination, and scaling issues. It provides guidelines for testing and calibration. Ultra high-speed imaging at frame rates exceeding 1 million frames per second is reviewed, and the combination of conventional experiments in fluids techniques with high-speed imaging techniques are discussed. The review is concluded with a high-speed imaging chart, which summarizes criteria for temporal scale and spatial scale and which facilitates the selection of a high-speed imaging system for the applicatio

Flexible Neural Electrode Array Based-on Porous Graphene for Cortical Microstimulation and Sensing.

Neural sensing and stimulation have been the backbone of neuroscience research, brain-machine interfaces and clinical neuromodulation therapies for decades. To-date, most of the neural stimulation systems have relied on sharp metal microelectrodes with poor electrochemical properties that induce extensive damage to the tissue and significantly degrade the long-term stability of implantable systems. Here, we demonstrate a flexible cortical microelectrode array based on porous graphene, which is capable of efficient electrophysiological sensing and stimulation from the brain surface, without penetrating into the tissue. Porous graphene electrodes show superior impedance and charge injection characteristics making them ideal for high efficiency cortical sensing and stimulation. They exhibit no physical delamination or degradation even after 1 million biphasic stimulation cycles, confirming high endurance. In in vivo experiments with rodents, same array is used to sense brain activity patterns with high spatio-temporal resolution and to control leg muscles with high-precision electrical stimulation from the cortical surface. Flexible porous graphene array offers a minimally invasive but high efficiency neuromodulation scheme with potential applications in cortical mapping, brain-computer interfaces, treatment of neurological disorders, where high resolution and simultaneous recording and stimulation of neural activity are crucial

Dispersive Fourier Transformation for Versatile Microwave Photonics Applications

Abstract: Dispersive Fourier transformation (DFT) maps the broadband spectrum of an ultrashort optical pulse into a time stretched waveform with its intensity profile mirroring the spectrum using chromatic dispersion. Owing to its capability of continuous pulse-by-pulse spectroscopic measurement and manipulation, DFT has become an emerging technique for ultrafast signal generation and processing, and high-throughput real-time measurements, where the speed of traditional optical instruments falls short. In this paper, the principle and implementation methods of DFT are first introduced and the recent development in employing DFT technique for widespread microwave photonics applications are presented, with emphasis on real-time spectroscopy, microwave arbitrary waveform generation, and microwave spectrum sensing. Finally, possible future research directions for DFT-based microwave photonics techniques are discussed as well

Measurements of wall-shear stress fields on the piston crown in an IC engine flow using fluorescent labelled micro-pillar imaging

The measurement of wall shear-stress along the crown of a moving piston is accomplished with an array of hair-like, flexible micro-pillar sensors (MPS) in an internal combustion (IC) engine during intake flow conditions. The MPS are wall-clamped flexible micro-cylinders of 20micron diameter made of polydimethylsiloxane (PDMS) positioned on the surface of a transparent planar piston crown and protruding into the boundary layer flow above the piston at a height of 390micron. Their tips are labelled with fluorophores and are illuminated with a scanning laser-sheet system that follows the piston motion in synchronous manner. The flow-induced deflection is recorded through the transparent piston crown from below with a compact shaft-mounted high-speed camera recording the fluorescent re-emitted light from the pillar tips and using the fact of optical wave-guide features of the transparent micro-pillars. The experiments were performed in a transparent 4-valve engine setup (1.6 liter Prince 2, N13B16) during the intake phase. In order to improve the temporal resolution, the running speed of the engine was scaled down using water as working liquid. A static and dynamic sensor-calibration enabled the precise measurements of the wall-shear stress distribution with the sensor array. Due to spatial resolution limits of current available compact high-speed camera the recorded region along the piston was limited to 4x2 mm2 with 8x4 pillars in full view. The recordings at 300fps show the WSS fluctuations induced by the valve-jet / piston-wall interaction in the beginning of the intake with strong wall-normal motion forming critical points in the WSS field such as saddles, nodes and foci. Over the intake cycle > CA 80° these fluctuations die out and flow is transformed into wall-parallel coherent motion prescribed by the formation of the tumble

Simultaneous capacitive probe and planar laser-induced fluorescence measurements in downwards gas-liquid annular flow

Various experimental techniques are available to analyse two-phase flows. The measurement concept and the applicability can however vary greatly. Prime examples from the opposite spectrum are planar laser-induced measurements (PLIF) versus capacitive probes. PLIF is an optical technique, it is non-intrusive but optical access is necessary. PLIF based measurements are known for their high temporal and spatial resolution but require a costly set-up. In contrast, the capacitive probe is another non-intrusive technique but doesn’t require optical access. It is fairly easy to set up, robust, and is cheap to construct. To rigorously compare both techniques, simultaneous PLIF and capacitive probe measurements are made in this work. As the void fraction is one of the key parameters to classify flow regimes, both techniques are compared on the determination of the void fraction. This is done for a limited set of six annular flows. The experiments were performed in a downward annular-flow facility with demineralized water - air as working medium. The first results indicate that both techniques give similar volume averaged void fractions. The mean absolute percentage error and the maximum relative error between both techniques are 0.30% and 0.54%, respectively. The PLIF measurements confirm however to have a better spatial resolution

Compressive Holographic Video

Compressed sensing has been discussed separately in spatial and temporal domains. Compressive holography has been introduced as a method that allows 3D tomographic reconstruction at different depths from a single 2D image. Coded exposure is a temporal compressed sensing method for high speed video acquisition. In this work, we combine compressive holography and coded exposure techniques and extend the discussion to 4D reconstruction in space and time from one coded captured image. In our prototype, digital in-line holography was used for imaging macroscopic, fast moving objects. The pixel-wise temporal modulation was implemented by a digital micromirror device. In this paper we demonstrate $10\times$ temporal super resolution with multiple depths recovery from a single image. Two examples are presented for the purpose of recording subtle vibrations and tracking small particles within 5 ms.Comment: 12 pages, 6 figure