Detection of DNA in a Nanopore Fabricated From Glass Tube

Nanopores are increasingly utilized as tools for single molecule detection in biotechnology. Here, we report an improved fabrication process to make solid-state nanopores from glass tubes with the help of paraffin. Based on the physical footprint of the phase change of the paraffin, nanocavity is formed in the broken terminal after thermally compressing and pulling the glass capillary. Nanopores with the minimum diameter of 20 nm are fabricated. The key step is to control the thickness of paraffin layer attached in the inner wall, which could affect the diameter of the nanopore. We investigate 48Kb λ-DNA molecules translocate through the fabricated glass nanopore. Because DNA molecules with the negative charges could be driven by the electrical force to pass through the nanopore and could physically block the pore to produce measurable changes in ionic currents. A transient electrical current changing is used to detect the DNA molecules in the solution. In the experiments, many events of DNA translocation were observed under the positive potential. We demonstrate that DNA molecules could be detected by the nanopore fabricated from glass tube. However, we also find the events of DNA translocation under the negative potential, which is because of the electro-osmotic flow (EOF) effects. It is found that the electro-osmotic flow inside the nanopore plays an important role in the DNA translocation process, and thus depends on the size of the pore. We shows that the effective driving force on DNA in a nanopore is the co-effects of the force of the electric field and the drag force of the electro-osmotic flow.

Evaporative Particle Deposition on Superhydrophobic Surfaces

The ability to control the size, shape, and location of particulate deposits is important in patterning, nanowire growth, sorting biological samples, and many other industrial and scientific applications. It is therefore of interest to understand the fundamentals of particle deposition via droplet evaporation. In the present study, we experimentally probe the assembly of particles on superhydrophobic surfaces by the evaporation of sessile water droplets containing suspended latex particles. Superhydrophobic surfaces are known to result in a significant decrease in the solid-liquid contact area of a droplet placed on such a substrate, thereby increasing the droplet contact angle and reducing the contact angle hysteresis. We conduct experiments on superhydrophobic surfaces of different geometric parameters that are maintained at different surface temperatures. The transient droplet shape and wetting behavior during evaporation are analyzed as a function of substrate temperature as well as surface morphology. During the evaporation process, the droplet exhibits a constant contact radius mode, a constant contact angle mode, or a mixed mode in which the contact angle and contact radius change simultaneously. The evaporation time of a droplet can be significantly reduced with substrate heating as compared to room-temperature evaporation. To describe the spatial distribution of the particle residues left on the surfaces, qualitative and quantitative evaluations of the deposits are presented. The results show that droplet evaporation on superhydrophobic surfaces, driven by mass diffusion under isothermal conditions or by substrate heating, suppresses particle deposition at the contact line. This preempts the so-called coffee-ring and allows active control of the location of particle deposition.

Hollow Fiber Membrane (HFM) Facilitated CO2 Delivery to a Cyanobacteria Layer for Biofuel Production

Photosynthetic bacteria have been shown to be advantageous organisms for biofuel production due to high CO2 fixation efficiencies, fast growth rates, and lower water requirements. Recently, cyanobacteria been metabolically engineered to efficiently secrete their products into a surrounding solution. This has the advantage of potentially eliminating the requirement to harvest and post-process the organisms in order to extract a biofuel, which is one of the most energy and water expensive processes in most biodiesel production strategies. Lagging behind the development of these organisms however has been the development of new photobioreactor (PBR) strategies that can efficiently delivery light and inorganic carbon to the bacteria while extracting the secreted product and O2 from the solution phase. Hollow fiber membranes (HFMs) are a method for bubble-less gas exchange that has been shown to be effective at enhancing mass transfer in applications such as wastewater and landfill treatment. HFM technology could be used to overcome the mass transport challenges associated with photobioreactors. HFM modules have been used to increase mass transfer of CO2 to the bulk media in bench scale PBRs; however, the use of HFM fibers as both a mean to exchange and deliver a gas phase throughout a PBR has not been explored. We have characterized the passive transport along a single fiber in a miniature reactor in previous work. Here we extend our work to arrays of HFM fibers. We performed a range of experiments to characterize bacteria growth rate and distribution as a function fiber spacing and active transport through the fibers, and report optimized values for these variables.

Sizing and Positioning Algorithm for 1 µm to 10 µm Particles Using Shadowgraphy

Measuring flows of aerosol particles of less than 10 μm diameter has proven a challenge in the past. Previously, our work included a brief review of the current state-of-art for aerosol measurements where accurate sizing was limited to particles greater than 5 μm. We developed a sizing and positioning algorithm (SPA) to accurately calculate both the diameter of a spherical particle, and the relative position of that particle to the object plane of the imaging camera for particles down to 3 μm in diameter. Our current work further extends the measurement range down to 1 μm particles. This algorithm has great benefit for the scientific community interested in small-particle aerosol flows.

LED Lumen Degradation and Remaining Life Under Exposure to Temperature and Humidity

The development of light-emitting diode (LED) technology has resulted in widespread solid state lighting use in consumer and industrial applications. Previous researchers have shown that LEDs from the same manufacturer and operating under same use-condition may have significantly different degradation behavior. Applications of LEDs to safety critical and harsh environment applications necessitate the characterization of failure mechanisms and modes. This paper focuses on a prognostic health management (PHM) method based on the measurement of forward voltage and forward current of bare LED under harsh environment. In this paper experiments have been done on single LEDs subjected to combined temperature-humidity environment of 85°C, 85% relative humidity. Pulse width modulation (PWM) control method has been employed to drive the bare LED in order to reduce the heat effect caused by forward current and high frequency (300Hz). A data acquisition system has been used to measure the peak forward voltage and forward current. Test to failure (luminous flux drops to 70 percent) data has been measured to study the effects of high temperature and humid environment loadings on the bare LEDs. A solid state cooling method with a peltier cooler has been used to control the temperature of the LED in the integrating sphere when taking the measurement of luminous flux. The shift of forward voltage forward current curve and lumen degradation has been recorded to help build the failure model and predict the remaining useful life. Particle filter has been employed to assess the remaining useful life (RUL) of the bare LED. Model predictions of RUL have been correlated with experimental data. Results show that prediction of remaining useful life of LEDs, made by the particle filter model works with acceptable error-bounds. The presented method can be employed to predict the failure of LED caused by thermal and humid stresses.

Design of an Ingestible Capsule With Wireless Communication and Powering Function for Obesity Treating

Intra-gastric balloons have been and effective and non-invasive method for morbid obesity treating since it is proposed. However, traditional balloons lead to complications such as nausea and sickness caused by insertion and removal endoscopes. Despite free of endoscope-guide insertion and removal process, wireless controlled balloons still have to face the problem of energy shortage. This paper proposes a novel wireless controlled and powered endoscope capsule of edible size. The performance of wireless control and powering are tested respectively. In addition, in-vivo and in-vitro experiments are conducted for further evaluation and shows feasibility for treating morbid obesity. This study may contribute to the development of endoscopic devices and surgery as well.

Fabrication of Hybrid Micro-Nanofluidic Devices With Centimeter Long Ultra-Low Aspect Ratio Nanochannels

Hybrid microfluidic and nanofluidic devices have a variety of applications including water desalination, molecular gates and DNA sieving among several other lab-on-chip uses. Most microfluidic and nanofluidic devices currently are fabricated in glass, silicon, polydimethylsiloxane (PDMS), or with a combination of these materials. In order to impart functionality, metals, polymers or auxiliary components are often integrated with these devices. Ultra-low aspect ratio channels have several advantages including critical dimensions on the nanoscale but increased throughput compared to higher aspect ratio channels with the same critical dimension, which is important for applications where a higher volumetric flow rate is desired. Additionally, theoretical analysis is significantly easier as ultra-low aspect ratio channels can be modeled as 1-D systems. The fabrication methods for achieving low aspect ratios (< 0.005) usually require extensive facilities with several innovative fabrication and bonding schemes being previously reported. In this paper, we report on fabrication and bonding of ultra-low aspect ratio microfluidic and nanofluidic devices with aspect ratios at 0.0005 in glass/PDMS devices in contrast to the previous best reported result of 0.005 achieved in a silica device using stamp and stick PDMS bonding. The simplicity of our approach presents a new pathway to achieving the lowest aspect ratio nanochannels ever reported for channels fabricated using an interfacial layer for bonding. Centimeter long nanochannels on a borosilicate substrate were fabricated by standard UV photolithography followed by wet etching. Surface roughness of the fabricated channels is on the same order as the roughness of the initial substrate (2–3 nm) and therefore can enable fabrication of channels with critical dimensions approaching 15 nm or less. Devices were then bonded using a second borosilicate substrate with a thin PDMS adhesion layer (∼ 2 μm). The PDMS adhesion layer allows rapid, facile, and alignment-free bonding compared to traditional fusion or anodic bonds. Successful verification of device operation and functionality was determined by verifying flow in operational devices and with scanning electron microscopy to confirm bonding for the formation of nanochannels.

A Sensitive Multiparametric Biosensor With Capabilities of Rapid Toxicity Detection of Drinking Water

Recently, there has been interest to develop biosensors based on live mammalian cells to monitor the toxicity of water. The cell viability after exposure to toxic water can be monitored by electric cell-substrate impedance sensing (ECIS) of the cell membrane. However, these impedance based toxicity sensors can only provide one single sensing endpoint (impedance measurement), and many toxicants cannot be detected at the concentration between Military Exposure Guideline levels and estimated Human Lethal Concentrations. The goal of this paper is to provide a rapid and sensitive sensing platform for long-term water toxicity detection. In this paper a novel multiparametric biosensor with integrated microfluidic channels for water toxicity detection is presented. Toxicity tests to study bovine aortic endothelial cells (BAECs) responsiveness to health-threatening concentrations of ammonia in de-ionized (DI) water will be presented. We demonstrated the BAECs can rapidly respond to ammonia concentrations between the military exposure guideline of 2mM and human lethal concentration of 55mM. The successful testing of water toxicity by simultaneous gravimetric and impedimetric measurements indicates that the multiparametric biosensor platform is able to perform rapid and sensitive detection of water toxicity and minimize the false-positive rate.

Wire-Electric Gyroscope

The wire-electric gyroscope (WEG) is a new type of the angular rate sensor. The basic principle of the WEG is based on the hypothesis of invariance of the electric current speed for the same wire (coil). It is similar to the Sagnac effect for the speed of light. The method of angular rate determination is described. The voltage difference between two wire coils with different line coupling can be expressed in applied rotation (angular) rate and velocity of electric current. The scale factor depends on the magnitude of the current, number of the coil turns, the coil’s radius, the cross-section area of the wire and specific (unit) resistance of the wire. WEG can be produced cost-effectively and can be a good choice for low-cost applications.

Micro Double Pressure Sensor for Measuring the Applying Forces in Balloon Angioplasty

This paper describes a new catheter based on double pressure sensor for measuring reaction forces of cardiovascular vessel walls in balloon angioplasty. This medical device is based on Wheatstone bridge and a passive transformer module. It assists cardiologists to measure reaction forces exiting between the catheter and the vascular wall. Reaction forces on the catheter can be grouped into two types: 1) reaction forces on the catheter head and 2) reaction forces between the balloon and the vascular wall. Its new proposed transducer module aids doctors decrease cardiology steps leading to the reduction of patients’ pains from inputting consecutive catheters into their bodies. Moreover, its special circuit design reduces needing wires for power supplying of the sensors, and simplifies the fabrication processes. Finally, mechanical behaviors of the sensor have been simulated in SolidWorks and its electrical circuit is modeled in Simulink\electrical. Also, Fabrication processes are projected in the final step of designing.