Printed Receive Coils with High Acoustic Transparency for Magnetic Resonance Guided Focused Ultrasound.

In magnetic resonance guided focused ultrasound (MRgFUS) therapy sound waves are focused through the body to selectively ablate difficult to access lesions and tissues. A magnetic resonance imaging (MRI) scanner non-invasively tracks the temperature increase throughout the tissue to guide the therapy. In clinical MRI, tightly fitted hardware comprised of multichannel coil arrays are required to capture high quality images at high spatiotemporal resolution. Ablating tissue requires a clear path for acoustic energy to travel but current array materials scatter and attenuate acoustic energy. As a result coil arrays are placed outside of the transducer, clear of the beam path, compromising imaging speed, resolution, and temperature accuracy of the scan. Here we show that when coil arrays are fabricated by additive manufacturing (i.e., printing), they exhibit acoustic transparency as high as 89.5%. This allows the coils to be placed in the beam path increasing the image signal to noise ratio (SNR) five-fold in phantoms and volunteers. We also characterize printed coil materials properties over time when submerged in the water required for acoustic coupling. These arrays offer high SNR and acceleration capabilities, which can address current challenges in treating head and abdominal tumors allowing MRgFUS to give patients better outcomes

Time-Dependent Physicochemical Changes of Carbonate Surfaces from SmartWater (Diluted Seawater) Flooding Processes for Improved Oil Recovery.

Over the past few decades, field- and laboratory-scale studies have shown enhancements in oil recovery when reservoirs, which contain high-salinity formation water (FW), are waterflooded with modified-salinity salt water (widely referred to as the low-salinity, dilution, or SmartWater effect for improved oil recovery). In this study, we investigated the time dependence of the physicochemical processes that occur during diluted seawater (i.e., SmartWater) waterflooding processes of specific relevance to carbonate oil reservoirs. We measured the changes to oil/water/rock wettability, surface roughness, and surface chemical composition during SmartWater flooding using 10-fold-diluted seawater under mimicked oil reservoir conditions with calcite and carbonate reservoir rocks. Distinct effects due to SmartWater flooding were observed and found to occur on two different timescales: (1) a rapid (<15 min) increase in the colloidal electrostatic double-layer repulsion between the rock and oil across the SmartWater, leading to a decreased oil/water/rock adhesion energy and thus increased water wetness and (2) slower (>12 h to complete) physicochemical changes of the calcite and carbonate reservoir rock surfaces, including surface roughening via the dissolution of rock and the reprecipitation of dissolved carbonate species after exchanging key ions (Ca2+, Mg2+, CO32-, and SO42- in carbonates) with those in the flooding SmartWater. Our experiments using crude oil from a carbonate reservoir reveal that these reservoir rock surfaces are covered with organic-ionic preadsorbed films (ad-layers), which the SmartWater removes (detaches) as flakes. Removal of the organic-ionic ad-layers by SmartWater flooding enhances oil release from the surfaces, which was found to be critical to increasing the water wetness and significantly improving oil removal from carbonates. Additionally, the increase in water wetness is further enhanced by roughening of the rock surfaces, which decreases the effective contact (interaction) area between the oil and rock interfaces. Furthermore, we found that the rate of these slower physicochemical changes to the carbonate rock surfaces increases with increasing temperature (at least up to an experimental temperature of 75 °C). Our results suggest that the effectiveness of improved oil recovery from SmartWater flooding depends strongly on the formation of the organic-ionic ad-layers. In oil reservoirs where the ad-layer is fully developed and robust, injecting SmartWater would lead to significant removal of the ad-layer and improved oil recovery

Physical principles for scalable neural recoding

Simultaneously measuring the activities of all neurons in a mammalian brain at millisecond resolution is a challenge beyond the limits of existing techniques in neuroscience. Entirely new approaches may be required, motivating an analysis of the fundamental physical constraints on the problem. We outline the physical principles governing brain activity mapping using optical, electrical, magnetic resonance, and molecular modalities of neural recording. Focusing on the mouse brain, we analyze the scalability of each method, concentrating on the limitations imposed by spatiotemporal resolution, energy dissipation, and volume displacement. Based on this analysis, all existing approaches require orders of magnitude improvement in key parameters. Electrical recording is limited by the low multiplexing capacity of electrodes and their lack of intrinsic spatial resolution, optical methods are constrained by the scattering of visible light in brain tissue, magnetic resonance is hindered by the diffusion and relaxation timescales of water protons, and the implementation of molecular recording is complicated by the stochastic kinetics of enzymes. Understanding the physical limits of brain activity mapping may provide insight into opportunities for novel solutions. For example, unconventional methods for delivering electrodes may enable unprecedented numbers of recording sites, embedded optical devices could allow optical detectors to be placed within a few scattering lengths of the measured neurons, and new classes of molecularly engineered sensors might obviate cumbersome hardware architectures. We also study the physics of powering and communicating with microscale devices embedded in brain tissue and find that, while radio-frequency electromagnetic data transmission suffers from a severe power–bandwidth tradeoff, communication via infrared light or ultrasound may allow high data rates due to the possibility of spatial multiplexing. The use of embedded local recording and wireless data transmission would only be viable, however, given major improvements to the power efficiency of microelectronic devices

Neural Dust: Ultrasonic Biological Interface

A seamless, high density, chronic interface to the nervous system is essential to enable clinically relevant applications such as electroceuticals or brain-machine interfaces (BMI). Currently, a major hurdle in neurotechnology is the lack of an implantable neural interface system that remains viable for a patient's lifetime due to the development of biological response near the implant. Recently, mm-scale implantable electromagnetics (EM) based wireless neural interfaces have been demonstrated in an effort to extend system longevity, but the implant size scaling (and therefore density) is ultimately limited by the power available to the implant. In this thesis, we propose neural dust, an entirely new method of wireless power and data telemetry using ultrasound, which can address fundamental issues associated with using EM to interrogate miniaturized implants. Key concepts and fundamental system design trade-offs and ultimate size, power, and bandwidth scaling limits of such system are analyzed from first principles. We demonstrate both theoretically and experimentally that neural dust scales extremely well, down to 100's, if not 10's of $\mu$m. We highlight first wireless recordings from nerve and muscle in an animal model using neural dust prototype. The thesis concludes with strategies for multi-neural dust interrogation and future directions of neural dust beyond neuromodulation

A terahertz imaging receiver in µm SiGe BiCMOS technology

This paper presents an integrated THz imaging receiver in bulk 0.13μm SiGe technology. The receiver, based on direct power detection, achieves a peak responsivity of 2.6MV/W and 700kV/W and a NEP of 8.7pW/√Hz and 32.4 pW/√Hz at 0.25 THz and 0.3 THz, respectively. No external silicon lens or post-processing, such as substrate thinning, was employed for improving antenna gain, efficiency and reducing power loss in substrate modes. To the best of the authors' knowledge, this is the lowest reported NEP in silicon at THz frequencies, without the use of expensive post-processing or external silicon lens

Distributed Active Radiator arrays for efficient doubling, filtering, and beam-forming

Distributed Active Radiator (DAR) arrays are demonstrated as novel ways of harmonic generation, radiation, and filtration to generate power at frequencies above the cut-off frequency of a technology. As proofs-of-concept, 2×1 and 2× 2 arrays of DAR with beam-forming are implemented on PCB, which are designed to oscillate at the fundamental frequency of 1.25GHz, while radiating (circularly-polarized) at the doubling frequency of 2.5GHz. The measured EIRP of 2× 1 and 2× 2 arrays are 7.46dBm and 12.96dBm, respectively, at 2.5GHz with a DC-to-radiated 2nd harmonic conversion of 0.8%. Almost 40° of beam-steering at 2.5GHz was measured in 2D space for the 2×2 array and more than 15dB suppression of the first and third harmonic compared to the desired second harmonic was measured in the radiated far-field

Silicon Integrated 280 GHz Imaging Chipset With 4x4 SiGe Receiver Array and CMOS Source

In this paper, we report an integrated silicon-based active imaging chipset with a detector array in 0.13 μm SiGe process and a CMOS-based source array operating in the 240-290 GHz range. The chipset operates at room-temperature with no external RF or optical sources, high-resistivity silicon lenses (HRSi) or waveguides or any custom fabrication options, such as high-resistivity substrates or substrate thinning. The receiver chip consists of a 2-D array of 16 pixels, measuring 2.5 mm × 2.5 mm with integrated antennas. An electromagnetic-active circuit co-design approach is carried out to ensure high-efficiency interface with detectors operating above cut-off frequencies with good impedance matching, near-optimal noise performance, while simultaneously suppressing the dominant surface-wave modes in a lensless lossy bulk silicon substrate. The array performance is characterized in the WR-3 band between 220-320 GHz. At the designed frequency of 260 GHz, the NEP of all pixels stays between 7.9 pW/√{Hz}-8.8 pW/√{Hz}. The imaging chipset consists of this 2D detector array chip and a CMOS-based source array chip measuring 0.8 mm × 0.8 mm. The entire system dissipates less than 180 mW of DC power, representing a truly integrated solution

Synthesis of PTFE based Air Cathode for Metal Air Battery

A large number of researchers devotes deep study to reducing the contact resistance and improving the durability of air cathode. Air cathode consists of gas diffusion layer, current collector and catalytic layers. The network structure (gas diffusion layer, GDL) of Air cathode plays an important role in metal-air battery. This GDL makes the air-cathode semi-permiable. It means that H2O does not pass through GDL layer but O2 moleecules can pass the layer. For that reason, the optimization of sintering condition is very important process in manufacturing Air cathode. This article is about the dependence of discharge property of magnesium air-battery to its sinter-ability. Thus in order to observe any changes in the discharge property, sinter-ability, a cost-effective method was designed in the air cathode production