Under certain conditions, electrophoretic deposition (EPD) of single-wall carbon nanotubes (SWCNTs) onto metal at the base of nanoscale insulating windows can result in a single SWCNT per window, bonded at one end to the metal. During EPD charge, buildup on the insulator creates electrostatic lenses at the windows that control the trajectory of the SWCNTs. The aim is to develop a reproducible process for deposition of individual vertically oriented SWCNTs into each window to enable novel devices. The length of the SWCNTs is shown to be the most critical parameter in achieving results that could be used for devices. In particular, single nanotube deposition in windows by EPD was achieved with SWCNTs with lengths on the order of the window depth. By performing current vs voltage (IV) measurements against a platinum wire in a phosphate buffer and by modeling the data, the presence of the nanotube can be detected, the contact interface can be studied, and the nanotube's viability for device applications can be determined. These results provide a basis for process integration of vertical SWCNTs using EPD.

Large classes of electronic, photonic, and acoustic crystals and quasi-crystals have been predicted to support topological wave-modes. Some of these modes are stabilized by certain symmetries but others occur as pure wave phenomena, hence they can be observed in many other media that support wave propagation. Surface water-waves are mechanical in nature but very different from the elastic waves, hence they can provide a new platform for studying topological wave-modes. Motivated by this perspective, we report theoretical and experimental characterizations of water-wave crystals obtained by periodic patterning of the water surface. In particular, we demonstrate the band structure of the spectra and existence of spectral gaps.

A sensor was tested subdural and in vitro, simulating a supine infant with a ventricular-peritoneal shunt and controlled occlusions. The variable MEMS capacitive device is able to detect and forecast blockages, similar to early detection procedures in cancer patients. For example, with gradual occlusion development over a year, the method forecasts a danger over one month ahead of blockage. The method also distinguishes between ventricular and peritoneal occlusions. Because the sensor provides quantitative data on the dynamics of the cerebrospinal fluid, it can help test new therapies and work toward understanding hydrocephalus as well as idiopathic normal pressure hydrocephalus. The sensor appears to be a substantial advance in treating brain injuries treated with shunts and has the potential to bring significant impact in a clinical setting.

A device, with MEMS sensors at its core, has been fabricated and tested for measuring low fluid pressure and slow flow rates. The motivation was to measure clinically relevant ranges of slow-moving fluids in living systems, such as the cerebrospinal fluid in the brain. For potential clinical utility, the device can be read transcutaneously by inductive coupling to MEMS capacitive sensors in circuits with resonance frequencies in the MHz range. Signal shifts for flow rates in the range of 0-42 mL/h and differential pressure levels between 0.1 and 2 kPa have been measured, because the sensitivity in the capacitance gap measurement is about 1 Å. The sensors have been used successfully to monitor simulated cerebrospinal fluid dynamics. The device does not utilize any internal power, since it is powered externally via the inductive coupling.

We have detected shunt occlusions in the range of 0 mm2 to 0.503 mm2. We have developed a method to monitor cerebrospinal fluid in clinically relevant ranges, including flow rates as low as 1 mL/hr and pressures in the range of 0.5 mmHg to 13.9 mmHg. This is done by utilizing capacitive biosensors that are equipped with flexible membranes spaced less than 1 µm apart. The capacitors are part of a resonant LC circuit and can be read transdermally in the MHz range with kHz precision via a custom external reader. This allows the device to function without need of a battery. Noninvasive monitoring of the fluid would provide physicians a useful way of diagnosing shunt malfunctions while preventing further brain injury from complications in patients affected by hydrocephalus as well as minimize unnecessary shunt revisions.

A flow sensor has been fabricated and tested that is capable of measuring the slow flow characteristic of the cerebrospinal fluid in the range from less than 4 mL/h to above 100 mL/h. This sensor is suitable for long-term implantation because it uses a wireless external spectrometer to measure passive subcutaneous components. The sensors are pressure-sensitive capacitors, in the range of 5 pF with an air gap at atmospheric pressure. Each capacitor is in series with an inductor to provide a resonant frequency that varies with flow rate. At constant flow, the system is steady with drift <0.3 mL/h over a month. At variable flow rate, V̇ , the resonant frequency, f0, which is in the 200-400 MHz range, follows a second order polynomial with respect to V̇ . For this sensor system the uncertainty in measuring f0 is 30 kHz which corresponds to a sensitivity in measuring flow of ΔV̇ = 0.6 mL/hr. Pressures up to 20 cm H2O relative to ambient pressure were also measured. An implantable twin capacitor system is proposed that can measure flow, which is fully compensated for all hydrostatic pressures. For twin capacitors, other sources of systematic variation within clinical range, such as temperature and ambient pressure, are smaller than our sensitivity and we delineate a calibration method that should maintain clinically useful accuracy over long times.

We present here the effects of Taxol, a cancer drug, on the intracellular mechanisms associated with dynamic instability of microtubules. Since Taxol affects the stability of microtubules, the general process of microtubule polymerization and depolymerization will be studied closely throughout this research project. By analyzing the dynamic instability of microtubules, the effects of Taxol on the microtubules can be used to elucidate the complex functioning of Taxol within the cell. The observations and discoveries of the research can have revolutionary effects in the fields of life science and medicine. The short-term goal of this project involves analysis of the thermal fluctuations of a single Taxol-stabilized microtubule. From our measurement of the elastic properties for Taxol-stabilized microtubules we can gain insight on vibrational modes of the microtubules. We propose that the vibrational modes of microtubules will vary based on the Taxol concentration at which they are grown and diluted. Then, by comparing the vibrational modes to the resonant frequency of the Taxol-stabilized microtubules, we will relate the dynamic instability of the microtubules to the change in vibrational mode. Therefore, the ultimate goal of the research is to acquire more knowledge about the function of Taxol in order to discover more effective cancer treatment methods. These findings will elucidate the confounding enigma that plagues humanity (cancer) and will lead to further advancements in cancer therapy research. Based on current findings, the microtubules grown with higher Taxol concentrations have lower Young's Modulus values.

Taxol is a drug used to treat cancer by stabilizing microtubules. The purpose of this research is to understand and explain how Taxol stabilizes microtubules and build a foundation upon which new discoveries involving cancer research can be made. We analyzed if Taxol affects the vibrational modes of microtubules by determining a frequency of Taxol-stabilized microtubules. Microtubules are grown, imaged, and analyzed by measuring the change of angle in radians of the end segments at 83ms intervals. The results depicted a sinusoidal movement of the end segment of the microtubule. From this, we found the resonant frequency by taking the Fourier Transform of the data and analyzing where the maximum peak occurred. The smaller peaks in the transform may be a result of the surrounding solution or internal fluctuations of the microtubule. We interpreted a 10.2 µm microtubule to have a frequency of 0.96 Hz. The process is repeated with microtubules of similar lengths, incubated with Taxol. We compared the resonant frequencies of the various lengths of microtubules and observed that there is a relationship between the length of a microtubule and its fundamental resonant frequency. The trend shows that as length of a microtubule increases, the fundamental frequency decreases.

A direct electron transfer biofuel cell consisting of a pair of single walled carbon nanotubes and enzymes on a single plane is reported, which allows for extremely close spacing of electrodes. The discrete device has a measured power and current density of 18 mW/cm2 and 90 mA/cm2, respectively, into 200 TΩ. Analysis of measurements from up to 3 million devices in parallel shows that the performance will improve by at least 2 orders of magnitude at peak power.

Electrical conductions in insulators such as resistance switching, conduction at interfaces, and conduction at domain boundaries and free surface of ferroelectrics are of interest. These conductions are often attributed to novel mechanism such as ferroelectric polarization. On the other hand, these interpretations appear not fully accepted, because the recent advanced theories of ferroelectric domains disregard screening indicated by these conduction phenomena. That is, these conduction phenomena are quietly regarded as the classical conduction originating from defects. In this paper, we examine these conductions in pure wide bandgap insulators in view of defects, using the direct-accessibility (tangibility) of conduction at free surfaces. Although most of these conductions in ferroelectrics may not be useful in large-scale applications, we show that they have fundamental implications on renovations of ferroelectric basics.

Noninvasive single cell electrical measurements using carbon nanotubes as electrodes are reported here. The device consists of four nanotubes deposited in the corner of a 2 micron square. Using flow, single cells are places on top of the electrodes. Two of the probes are used to apply voltage pulses to the cell and the other two are used to measure the response as a function of time. As a control, measurements of water, cell medium, cells and biomolecules have been made with metallic plates, defined by 60nm holes in a 75nm insulating film. For proof of principle, yeast cells suspended in HEPES are measured. The results show that the nanotubes allow a contact with the ionic environment 100 times better than the metallic plates. The nanotubes also show a different response when the cell is nearby or touching a cell. Since the nanotubes are 1.2 nm in diameter, comparable in size with membrane proteins, we plan to use the nanotube array to perform some of the functions of patch clamps but with less perturbation to the cells due to the small dimension of carbon nanotubes.

The region near a yeast cell has been probed by a pair of electrically conducting probes that are 2 microns apart -- closer than the cell diameter. The C-nanotubes are 1.2 nm in diameter -- of the size of molecules in the cell wall and able to sense their environment without damaging the cell. As a control, measurements of water and cell medium with micron-size metallic strips, but without the nanotubes present, were made. To test the nano-probes in a controlled way, they were attached to the metallic strips and then immersed in the test fluids. The results show that the nanotubes play a key role in the observed complex impedance. Then, the signal was compared for water, medium and yeast cells added to the medium. Layers of stationary fluids a few microns deep were measured as a function of frequency from 10 to 10,000 Hz, (similar to dielectric susceptibility in large collections of cells). The results show that the susceptibility differences were largest in the frequency range from 10 to 1000Hz, with the average impedance with cells about a factor of 4 higher than that with just medium and a factor of 2 larger than with water. The results indicate that the nanoprobes record a signal due to the presence of the cells, with weighting toward the nearest cell. Finally, we flowed the medium with a low density of cells past the nanoprobes and recorded the complex impedance at 100Hz. Dynamic fluctuations in the signal were observed as the cells moved by, with somewhat larger changes when a cell was near the probe, as indicated by video-microscopy paired with the electrical record. Results indicate that the protocol is applicable to other types of cells.

Here we present a carbon nanotube based device to noninvasively and quickly detect mobile single cells with the potential to maintain a high degree of spatial resolution. The device utilizes standard complementary metal oxide semiconductor (CMOS) technologies for fabrication, allowing it to be easily scalable (down to a few nanometers). Nanotubes are deposited using electrophoresis after fabrication in order to maintain CMOS compatibility. The devices are spaced by 6 μm which is the same size or smaller than a single cell. To demonstrate its capability to detect cells, we performed impedance spectroscopy on mobile human embryonic kidney (HEK) cells, neurons cells from mice, and yeast cells (S. pombe). Measurements were performed with and without cells and with and without nanotubes. Nanotubes were found to be crucial to successfully detect the presence of cells. The devices are also able to distinguish between cells with different characteristics.