Nucleic acid delivery with microbubbles and ultrasound http://www.sciencedirect.com/science/article/pii/S0169409X14000106 Nucleic acid-based therapy is a growing field of drug delivery research. Although ultrasound has been suggested to enhance transfection decades ago, it took a combination of ultrasound with nucleic acid carrier systems (microbubbles, liposomes, polyplexes, and viral carriers) to achieve reasonable nucleic acid delivery efficacy. Microbubbles serve as foci for local deposition of ultrasound energy near the target cell, and greatly enhance sonoporation. The major advantage of this approach is in the minimal transfection in the non-insonated non-target tissues. Microbubbles can be simply co-administered with the nucleic acid carrier or can be modified to carry nucleic acid themselves. Liposomes with embedded gas or gas precursor particles can also be used to carry nucleic acid, release and deliver it by the ultrasound trigger. Successful testing in a wide variety of animal models (myocardium, solid tumors, skeletal muscle, and pancreas) proves the potential usefulness of this technique for nucleic acid drug delivery. ---------------------------- A novel transfection method for eukaryotic cells using polyethylenimine coated albumin microbubbles http://www.sciencedirect.com/science/article/pii/S0147619X11000230 Albumin microbubbles have been intensively studied for their application in gene delivery. However, with negative surface potential, albumin microbubbles hardly bind plasmid DNA, which might contribute to their low transgene efficiency. In this study, we developed polyethylenimine (PEI) coated albumin microbubbles (PAMB) which were prepared by sonicating the mixture of human albumin, PEI, polyethylene glycol and glucose. CHO cells, COS cells and 293T cells were transfected with PEI, PEI + albumin, PAMB and Lipofectamine 2000, respectively. Our results showed that the surface potential was elevated and PAMB could bind plasmid DNA. The transgene efficiency of PAMB was higher than PEI and PEI + albumin (P < 0.05), and PAMB performed the same transgene effect as Lipofectamine 2000 did but with lower cytotoxicity than Lipofectamine 2000. Albumin microbubbles modified by PEI has high transgene efficiency and low cytotoxicity even without ultrasound medication, making it a useful non-virus gene delivery method in vitro. ---------------------------------------- ultrasound sonoporation sonoluminescence sonography ultrasonography ---------------------------------------- Freehand 3D Ultrasound Reconstruction Algorithms—A Review Three-dimensional (3D) ultrasound (US) is increasingly being introduced in the clinic, both for diagnostics and image guidance. Although dedicated 3D US probes exist, 3D US can also be acquired with the still frequently used two-dimensional (2D) US probes. Obtaining 3D volumes with 2D US probes is a two-step process. First, a positioning sensor must be attached to the probe; second, a reconstruction of a 3D volume can be performed into a regular voxel grid. Various algorithms have been used for performing 3D reconstruction based on 2D images. Up till now, a complete overview of the algorithms, the way they work and their benefits and drawbacks due to various applications has been missing. The lack of an overview is made clear by confusions about algorithm and group names in the existing literature. This article is a review aimed at explaining and categorizing the various algorithms into groups, according to algorithm implementation. The algorithms are compared based on published data and our own laboratory results. Positive and practical uses of the various algorithms for different applications are discussed, with a focus on image guidance. (E-mail: ole.v.solberg@sintef.no) Real-time visualized freehand 3D ultrasound reconstruction based on GPU Unified reconstruction framework for multi-modal medical imaging Realistic fetus skin color processing for ultrasound volume rendering Real-time reconstruction and visualization of navigated 3D ultrasound images USB ultrasound probes http://ultrasound.engineering.wustl.edu/index.php/Open_Source_Development http://www.interson.com/Products/USBProbes/tabid/56/Default.aspx http://www.cse.wustl.edu/~dzar/Ultrasound/Downloads/USBProbeProgrammerV2.pdf -------------------- Design and fabrication of nanoscale ultrasonic transducers http://iopscience.iop.org/1742-6596/353/1/012001/pdf/1742-6596_353_1_012001.pdf http://iopscience.iop.org/1742-6596/353/1/012001 10-50 GHz The development of nanometre sized ultrasonic transducers is important in both biological and industrial applications. The small size can be important in its own right or necessary in order to generate acoustic waves with nanometric wavelengths. Potential applications of nanotransducers range from embedded sensors through to sub optical wavelength acoustic imaging. In this paper we discuss the design and fabrication of nanoscale ultrasonic transducers. The transducers rely on optical and mechanical resonances, they can be used to generate and detect high frequency ultrasound in a sample. The mechanical and optical performance of the devices have been extensively modelled using both analytical techniques and finite element modelling. This allows the fine tuning of the design parameters to ensure optimised performance for the experimental configuration. The devices can be fabricated in a number of ways, we present one method for building these types of devices, a ‘top down’ approach where plate structures are built up and patterned using standard photolithographic techniques. This method produces nanoscale devices in one dimension only (the others being a few microns) but produces excellent devices for testing in situ and for comparison to the models as they are easy to handle and measure. Approaches for reducing the other dimensions to the nanoscale will also be considered. ------------------------ PZT-epoxy piezoelectric transducers: a simplified fabrication procedure http://www.sciencedirect.com/science/article/pii/0025540881902671 Composite piezoelectric transducers have been constructed by partially dicing PZT ceramics and back-filling with epoxy. Composites containing 10 to 70 volume percent PZT were prepared with several different rod diameters. Measured dielectric constants ranged from 200 to 1000, longitudinal piezoelectric coefficients d33 from 200 to 350 pC/N, and hydrostatic piezoelectric coefficients dh from 40 to 80 pC/N. Piezoelectric properties are compared with solid PZT and with 3-1 composites made by extrusion. --------------------------- https://www.google.com/patents/US4773140 ---------------------------- http://techdigest.jhuapl.edu/TD/td2803/37ArveloOptimizing.pdf Recently, there has been some interesting work on piezoelectricity in polypropylene foam, also called cellular polypropylene (PP), or voided low-density polypropylene (LDPP). The new material consists of air bubbles introduced into polypropylene. This sheet of voided material is then biaxially stretched to elongate the voids (Fig. 1). After this material is stretched, a strong electric field is applied via a corona that exceeds the dielectric breakdown strength of the air inside the voids. The charges are forced to the polymer frame by the electric field, and the temperature is cooled, thus creating permanent electric charges along these boundaries. Because the sides of the voids have opposite charges, the charged voids become synthetic macroscopic dipoles. When an external force is applied to this material, the voids are narrowed, causing stronger dipole strength, and produce a compensating charge on the electrodes at the extreme boundaries of the material. It also is believed that there is an additional redistribution of the charges along the voids as well. This hypothesis was put forth to explain measurements of the material's piezoelectric constant and stiffness (Fig. 2). Busch-Vishniac, West, and Wallace [2] applied these polymer transducer materials in an array of designs and other applications. [2] Busch-Vishniac, I. J., West, J. E., and Wallace, R. L., "A new approach to transducer design applied to a foil electret acoustic antenna," J. Acoust. Soc. Am. 76, 1609-1616 (1984). A new approach to transducer design applied to a foil electret acoustic antenna Polymer piezoelectric materials for lightweight, rugged, and inexpensive transducers Optimizing voided piezoelectric polymers for acoustic sensors Focusing ultrasound with an acoustic metamaterial network --------------------------------- polyvinylidene fluoride (PVDF) PVDF-TrFE thin films PZT Efficient energy harvesting from human motion using wearable piezoelectric shell structures Piezoelectric shell structures as wearable energy harvesters for effective power generation at low-frequency movement Design of a piezoelectric based tactile sensor with bio-inspired micro/nano-pillars Magnetocaloric piezoelectric composites for energy harvesting Develop flexible piezoelectric PVDF nano-fibrous membrane The breakdown threshold of dielectric barrier discharges in piezoelectric polymer foams An evaluation on low-level vibration energy harvesting using piezoelectret foam Photoacoustic imaging with a commercial ultrasound system and a custom probe ;;break Confinement in oriented mesopores induces piezoelectric behavior of polymeric nanowires http://pubs.acs.org/doi/abs/10.1021/cm302594s We report on the preparation and the piezoelectric properties of ultrathin polymeric nanowires in the oriented pores of mesoporous silica, which are embedded in the channels of a supporting anodic alumina membrane. Poly(vinylidene difluoride) [PVDF] and its copolymer, poly(vinylidene difluoride trifluoroethylene) [PVTF], were both confined to two types of columnar silica mesopores of 5 and 10 nm in diameter. The extreme spatial confinement induces a preferential orientation of the crystalline domains of the polymer into a ferroelectric phase, leading to ultrahigh-aspect-ratio nanowires distributed throughout the templating host, and having up to 60 μm in length, comparable to the thickness of the hosting alumina. The resulting distributed array of piezoelectric nanowires are isolated from each other by a dielectric matrix, facilitating the handling and electrical contacting. We show, for the first time, that a remarkable piezo-response, in the absence of any poling or stretching, is obtained upon nanoconfinement on the PVDF polymer, which, in contrast, does not show any polarization when in bulk or film form without poling. The piezoelectric behavior was assessed by a piezo evaluation system (PES) and we visualized polar nanowire bundles via piezoresponse force microscopy (PFM). This “nano-structuration” represents a powerful approach, holding promise for applications for nanoactuators or bioinspired ciliated sensors with high sensitivity and resolution. Nanoconfinement: an effective way to enhance PVDF piezoelectric properties Confinement Induced Preferential Orientation of Crystals and Enhancement of Properties in Ferroelectric Polymer Nanowires Different scale confinements of PVDF-TrFE as functional material of piezoelectric devices Theoretical modeling and experiments on the piezoelectric coefficient in cellular polymer films Local piezoelectric response of ZnO nanoparticles embedded in a photosensitive polymer Fabrication of drug-loaded polymer microparticles with arbitrary geometries using a piezoelectric inkjet printing system ;;break Arrays of indefinitely long uniform nanowires and nanotubes http://bg.unam.bilkent.edu.tr/files/papers/Bayindir%20Group%20-%20Arrays%20of%20indefinitely%20long%20uniform%20nanowires%20and%20nanotubes%20Supplementary%20information.pdf http://www.nature.com/nmat/journal/v10/n7/abs/nmat3038.html Nanowires are arguably the most studied nanomaterial model to make functional devices and arrays1, 2. Although there is remarkable maturity in the chemical synthesis of complex nanowire structures3, 4, their integration and interfacing to macro systems with high yields and repeatability5, 6, 7 still require elaborate aligning, positioning and interfacing and post-synthesis techniques8, 9. Top-down fabrication methods for nanowire production, such as lithography and electrospinning, have not enjoyed comparable growth. Here we report a new thermal size-reduction process to produce well-ordered, globally oriented, indefinitely long nanowire and nanotube arrays with different materials. The new technique involves iterative co-drawing of hermetically sealed multimaterials in compatible polymer matrices similar to fibre drawing. Globally oriented, endlessly parallel, axially and radially uniform semiconducting and piezoelectric nanowire and nanotube arrays hundreds of metres long, with nanowire diameters less than 15 nm, are obtained. The resulting nanostructures are sealed inside a flexible substrate, facilitating the handling of and electrical contacting to the nanowires. Inexpensive, high-throughput, multimaterial nanowire arrays pave the way for applications including nanowire-based large-area flexible sensor platforms, phase-changememory, nanostructure-enhanced photovoltaics, semiconductor nanophotonics, dielectric metamaterials,linear and nonlinear photonics and nanowire-enabled high-performance composites. A nanoscale combing technique for the large-scale assembly of highly aligned nanowires http://cmliris.harvard.edu/assets/nnano_21Apr13ASAP_Jun.pdf The controlled assembly of nanowires is a key challenge in the development of a range of bottom-up devices1, 2. Recent advances2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 in the post-growth assembly of nanowires and carbon nanotubes have led to alignment ratios of 80–95% for a misalignment angle of ±5° (refs 5, 12, 13, 14) and allowed various multiwire devices to be fabricated6, 10, 11, 12, 13, 19. However, these methods still create a significant number of crossing defects, which restricts the development of device arrays and circuits based on single nanowires/nanotubes. Here, we show that a nanocombing assembly technique, in which nanowires are anchored to defined areas of a surface and then drawn out over chemically distinct regions of the surface, can yield arrays with greater than 98.5% of the nanowires aligned to within ±1° of the combing direction. The arrays have a crossing defect density of ~0.04 nanowires per µm and efficient end registration at the anchoring/combing interface. With this technique, arrays of single-nanowire devices are tiled over chips and shown to have reproducible electronic properties. We also show that nanocombing can be used for laterally deterministic assembly, to align ultralong (millimetre-scale) nanowires to within ±1° and to assemble suspended and crossed nanowire arrays. Self-integration of nanowires into circuits via guided growth https://www.weizmann.ac.il/materials/ernesto/pdfs/p50.pdf http://www.pnas.org/content/110/38/15195.short The ability to assemble discrete nanowires (NWs) with nanoscale precision on a substrate is the key to their integration into circuits and other functional systems. We demonstrate a bottom–up approach for massively parallel deterministic assembly of discrete NWs based on surface-guided horizontal growth from nanopatterned catalyst. The guided growth and the catalyst nanopattern define the direction and length, and the position of each NW, respectively, both with unprecedented precision and yield, without the need for postgrowth assembly. We used these highly ordered NW arrays for the parallel production of hundreds of independently addressable single-NW field-effect transistors, showing up to 85% yield of working devices. Furthermore, we applied this approach for the integration of 14 discrete NWs into an electronic circuit operating as a three-bit address decoder. These results demonstrate the feasibility of massively parallel “self-integration” of NWs into electronic circuits and functional systems based on guided growth. A nanoscale combing technique for the large-scale assembly of highly aligned nanowires http://cmliris.harvard.edu/assets/nnano_21Apr13ASAP_Jun.pdf Thermal drawing of high-density macroscopic arrays of well-ordered sub-5-nm-diameter nanowires http://www.creol.ucf.edu/Research/Publications/5069.pdf nanowire arrays nanowire synthesis guided growth microwires microwire array of PZT ? microwire synthesis ? piezoelectric microwire array nanorod array piezoelectric nanorod array piezoceramic piezoelectric piezopolymeric Ultra-long, free-standing, single-crystalline vanadium dioxide micro/nanowires grown by simple thermal evaporation http://www.me.berkeley.edu/~jwu/publications/Cheng-APL-2012.pdf ;;break Ultrasonic imaging of the internal vibration of soft tissue under forced vibration http://scitation.aip.org/content/asa/journal/jasa/84/S1/10.1121/1.2025806 To estimate the dynamic properties of soft tissues, an imaging system that can display both the amplitude and phase distributions of vibration in soft tissues under forced vibration was developed. In this method, low‐frequency sinusoidal vibration with a frequency from 10 Hz to 1 kHz is applied from the surface of the sample, and the movement in it is measured using simultaneously transmitted probing ultrasonic waves. Then scatterers in the sample move sinusoidally under the forced vibration, and the reflected ultrasonic waves are subject to the frequency modulation by the Doppler effect. The amplitude of vibration is estimated from the frequency modulation index of the reflected waves. This is derived from the amplitudes of the spectrum components of the output of the quadrature detector of the received signal. On the other hand, the phase of vibration is estimated from the angle of the fundamental spectrum component. Basic experiments have been carried out using a 3.0‐MHz ultrasonic wave system. The accuracy of the method is evaluated and two‐dimensional color maps of the amplitude and phase are shown for several phantoms, as well as tissues, in vivo. ;;break 40-MHz annular array imaging of mouse embryos http://www.sciencedirect.com/science/article/pii/S0301562906016334 Ultrasound biomicroscopy (UBM) has emerged as an important in vivo imaging approach for analyzing normal and genetically engineered mouse embryos. Current UBM systems use fixed-focus transducers, which are limited in depth-of-focus. Depending on the gestational age of the embryo, regions-of-interest in the image can extend well beyond the depth-of-focus for a fixed-focus transducer. This shortcoming makes it particularly problematic to analyze 3-D data sets and to generate accurate volumetric renderings of the mouse embryonic anatomy. To address this problem, we have developed a five-element, 40-MHz annular array transducer and a computer-controlled system to acquire and reconstruct fixed- and array-focused images of mouse embryos. Both qualitative and quantitative comparisons showed significant improvement with array-focusing, including an increase of 3 to 9 dB in signal-to-noise ratio and an increase of at least 2.5 mm in depth-of-focus. Volumetric-rendered images of brain ventricles demonstrated the clear superiority of array-focusing for 3-D analysis of mouse embryonic anatomy. (E-mail: turnbull@saturn.med.nyu.edu) In vivo 3d quantitative analysis of the mouse embryonic brain with a 38 mhz annular array and coded excitation Flexible Annular-Array Imaging Platform for Micro-Ultrasound http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3738186/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3738186/pdf/nihms-501970.pdf Development of a 12 element annular array transducer for realtime ultrasound imaging ;;break 3D Ultrasound Imaging System using Fresnel Ring Array 3D Ultrasound Imaging System using Fresnel Ring Array & High Voltage Multiplexer IC 256×256 2-D array transducer with row-column addressing Theoretical Assement of a Crossed Electrode 2- D Array for 3-D Imaging Dual-Layer Transducer Array for 3-D Imaging 10. Tamano S, Yamazaki M, Sano S, Hara K, Sakano J, Miwa Y. 3D Ultrasound Imaging System using Fresnel Ring Array. 2003 IEEE Ultrasonics Symposium; pp. 1310–1313. 11. Tamano S, Kobayashi T, Sano S, Hara K, Sakano J, Azuma T. 3D Ultrasound Imaging System using Fresnel Ring Array & High Voltage Multiplexer IC. 2004 IEEE Ultrasonics Symposium; pp. 782–785. A 256×2562-D array transducer with Row-column addressing for 3-D Rectilinear Imaging http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2894030/#R10 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2894030/pdf/nihms211419.pdf We present simulation and experimental results from a 5 MHz, 256 × 256 2-D (65,536 elements, 38.4 mm × 38.4 mm) 2-D array transducer with row-column addressing. The main benefits of this design are a reduced number of interconnects, a modified transmit/receive switching scheme with a simple diode circuit, and an ability to perform volumetric imaging of targets near the transducer with transmit beamforming in azimuth and receive beamforming in elevation. The final dimensions of a transducer were 38.4 mm × 38.4 mm × 300 μm. After prototyping a row-column transducer, the series resonance impedance was 104 Ω at 5.4 MHz. The measured -6 dB fractional bandwidth was 53% with a center frequency of 5.3 MHz. The SNR at the transmit focus was measured to be 30 dB. At 5 MHz, the average nearest neighbor crosstalk was -25 dB. In this paper, we present 3-D images of 5 pairs of nylon wires embedded in a clear gelatin phantom and of an 8 mm diameter cylindrical anechoic cyst phantom acquired from a 256 × 256 2-D array transducer made from a 1–3 composite. We display the azimuth and elevation B-scans as well as the C-scan. The cross-section of the wires is visible in the azimuth B-scan while the long axes can be seen in the elevation B-scan and C-scans. The pair of wires with 1 mm axial separation is discernible in the elevational B-scan while all the pairs of wires were distinguishable in the short-axis B-scan. Using a single wire from the wire target phantom, the measured lateral beamwidth was 0.68 mm and 0.70 mm at 30 mm depth in transmit beamforming and receive beamforming respectively compared to the simulated beamwidth of 0.55 mm. The cross-section of the cyst is visible in the azimuth B-scan while the long axes can be seen in the elevation B-scan and C-scans as a rectangle. However, it has not been demonstrated whether developing a fully sampled 2-D array would be feasible because of the difficulty in fabricating an array with such a large number of elements. The high electrical impedance due to the small size of each element would result in signal loss. To handle such a large array, one would need as many as 65,536 channels and tens of thousands of coaxial cables in an imaging system create a major challenge. One well established technique to overcome these difficulties is by using a sparse 2-D array [6–8]. Yen and Smith investigated several sparse 2-D array designs for real time volumetric imaging [6] and used the Mills-cross design to build a curvilinear array for 3-D ultrasound [7]. In the later version of the rectilinear 3D scanner, a sparse periodic array with receive mode multiplexing was built to improve spatial resolution performance [8]. However, extreme sparseness, with less than 10 % active elements, causes grating lobes and high clutter levels. This results in degradation of image contrast and hence limits the diagnostic value of the exam. Taking advantage of integrated circuit (IC) fabrication techniques, recent commercial systems use integrated electronics to allow connecting to approximately 3,000 individual elements before funneling the signals from these elements into 128 system channels via switches and preliminary beamformation within the handle [9]. The preliminary beamformation is located within the transducer handle using application specific integrated circuits (ASICs). The second stage of beamformation is done by a traditional 128 channel system digital beamformer providing dynamic focusing and full aperture delays. Tamano et al. developed a convex 2-D array in which switches connect elements in rings around the beam center similar to an annular array [10, 11]. Changing a steering direction or transmit focus is accomplished by reconfiguring the switches. ;;break Ultrasound as a Mechanical Method for Male Dog Contraception http://onlinelibrary.wiley.com/doi/10.1111/j.1439-0531.2009.01426.x/abstract The efficacy of ultrasound treatment as a reversible male contraceptive in the rhesus monkey http://www.biomedcentral.com/content/pdf/1477-7827-10-81.pdf