Haim Bau

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Papers by Haim Bau

The Chaos Theory and its Application

Journal of Physics: Conference Series, 2021

Chaos Theory is not only one of the most active branches of the dynamical system, but also one of... more Chaos Theory is not only one of the most active branches of the dynamical system, but also one of the most important topics of the nonlinear scientific field. The main purpose of this thesis is to introduce and illustrate the basic concepts, characteristics, and various applications of Chaos Theory. Chaos Theory is widely applied in physics, biology, and economics fields etc., so the thesis will also exhibit interdisciplinary research on Chaos Theory. The conclusion is that the most important refinement of Chaos Theory is its sensitivity to initial values, and subtle changes will affect the final shape and state of the entire structure.

On the Surface Tension of Nanobubbles

Bulletin of the American Physical Society, Nov 26, 2013

ROSS, IBM T.J. Watson Research Center -Using our custom-made liquid cell, the nanoaquarium [1], w... more ROSS, IBM T.J. Watson Research Center -Using our custom-made liquid cell, the nanoaquarium [1], we imaged with a transmission electron microscope the formation, growth, and detachment of single nanobubbles, nucleating in a supersaturated aqueous solution [2]. The supersaturation results from electron-induced radiolysis of water. The bubbles are first observed when their radii are about 20nm and detach when their radii are about 200nm. Based on our experimental data, we determined the bubbles' growth rates as functions of time, and found the growth rates to be highly reproducible and nearly independent of time (and bubbles' radii). Comparison of the theoretical predictions for bubble growth rate with our experimental observations suggests that the surface tension of the bubble-liquid interface must depend on the bubble's radius.

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Supplementary material from "Terrain following and applications: Caenorhabditis elegans swims along the floor using bump and undulate strategy

Nematodes such as <i>Caenorhabditis elegans</i> are heavier than water. When submerge... more Nematodes such as <i>Caenorhabditis elegans</i> are heavier than water. When submerged in water, they settle to the bottom surface. Observations reveal that the animals do not lie flat on the bottom surface, but remain substantially suspended above the surface through continuous collisions with the surface, while maintaining their swimming gaits. Consequently, the swimming animals follow the bottom surface topography. When the bottom surface is inclined, the animals swim up or down along the incline. As the magnitude of the gravitational force can be readily estimated, this behaviour provides a convenient means to estimate the animal's propulsive thrust. Animals' tendency to follow surface topography provides a means to control swimmers' trajectories and direction of motion, which we demonstrate with a saw tooth-like ratchet that biases the animals to swim in a selected direction. The animals also can serve as surface topography probes since their residence-time as a function of position provides information on surface features. Finally, we take advantage of surface following to construct a simple motility-based sorter that can sort animals based on genotype and state of health.

Nano bubble migration in a tapered conduit in the asymptotic limits of zero capillary and Bond Numbers - Theory and Experiments

Bulletin of the American Physical Society, Nov 23, 2015

Using a hermetically sealed liquid cell, we observed the growth and migration of bubbles (tens to... more Using a hermetically sealed liquid cell, we observed the growth and migration of bubbles (tens to hundreds of nanometers in diameter) in a tapered conduit and supersaturated solution with a transmission electron microscope. To better understand bubble shape and migration dynamics, we developed simple 2D and 3D models valid in the limit of zero capillary and Bond numbers. The 3D model is restricted to small taper slope, weakly non-circular contact line geometries and large bubble aspect ratio (high confinement), and was solved using a pseudo-spectral decomposition. Both models utilize the Blake-Haynes mechanism to relate dynamic contact angle to local contact line velocity The influence of pinning of a portion of the contact line on bubble geometry is also considered. Contact line dissipation controls curvature and regulates growth rate. Our 2D and 3D models predict growth rates in agreement with experimental observations, but several orders of magnitude lower than predicted by the classical Epstein -Plesset theory.

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Observations of Simple and Complex Liquid Transport in Carbon Nanotubes

Bulletin of the American Physical Society, Mar 23, 2005

Observations of Simple and Complex Liquid Transport in Carbon Nanotubes 1 BYONG KIM, SHASHANK SIN... more Observations of Simple and Complex Liquid Transport in Carbon Nanotubes 1 BYONG KIM, SHASHANK SINHA, HAIM BAU, University of Pennsylvania -Taking advantage of the optical transparency of template grown, carbon nanotubes (CNTs) with 15 nm thick walls, we studied experimentally and theoretically the capillary filling, condensation, and evaporation of glycerin, ethylene glycol, and DI water inside CNTs under room conditions [1]. All the liquids readily filled the CNTs by the action of capillary forces. The capillary filling was also used to study the filling of the tube with nanoparticles. Liquid, laden with 40nm-diameter fluorescent beads, was brought into contact with a 300nm diameter CNT. The liquid and the particles' transport were observed, respectively, with optical and fluorescence microscopy. Finally, a nanotube-based device that enables us to conduct controlled experiments of liquid and macromolecule transport with an electron microscope is described. [1] B. M. Kim, S. Sinha, and H. H. Bau, Nano Letters, 4, 2203 (2004).

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A Thermal Cycler Fabricated With Low Temperature, Co-Fired Ceramic Tapes

Micro-Electro-Mechanical Systems (MEMS), Nov 14, 1999

A thermal cycler fabricated with low temperature, co-fired, ceramic tapes is described. The monol... more A thermal cycler fabricated with low temperature, co-fired, ceramic tapes is described. The monolithic device consisted of a flow conduit, a resistor (Joule) heater, a thermistor, and conductors. A microprocessor was used to control the device’s temperature according to a pre-programmed temperature protocol. The device’s thermal performance was modeled, and the theoretical predictions were compared with experimental observations. As an example of an application, the device was used to carry out a polymerase chain reaction in which a non detectable concentration of a DNA segment was sufficiently amplified so as to enable separation and detection by electrophoresis.

Nanoscale evolution of interface morphology during electrodeposition

Nature Communications, Dec 19, 2017

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Theoretical and Experimental Study of Mesoscopic Impactors

An inertial impactor is a device that separates particles from a gas stream according to their ma... more An inertial impactor is a device that separates particles from a gas stream according to their mass. The characteristics of two different types of mesoscopic impactors, one with and one without a collection cup, were studied theoretically and experimentally. The theoretical study consists of a numerical solution of the Navier-Stokes equations for the fluid’s flow field and a solution of Newton’s equation of motion for the particles. The particle cut-off sizes and the impactor’s efficiency curves were computed as functions of the jet-to-plate distance, nozzle size, cup size, and the jet’s Reynolds number (Re < 100). Prototypes of impactors were fabricated in low temperature co-fired ceramic tapes. Preliminary experiments were carried out to determine the collection efficiency as a function of particle size and the Reynolds number. The experimental results were critically compared with theoretical predictions.

Meso-Scale Electromagnetic Actuators Fabricated in Low-Temperature Co-Fired Ceramic Tapes

Meso-scale electromagnetic actuators in low-temperature co-fired ceramic (LTCC) tapes were fabric... more Meso-scale electromagnetic actuators in low-temperature co-fired ceramic (LTCC) tapes were fabricated, tested, and analyzed. Two types of designs were considered: a NdFeB permanent magnet bonded to Kapton (polyimide film material from Du Pont) beam and a permalloy (soft magnetic material) beam. In both cases, electromagnetic coils printed on ceramic tapes were used for actuation. The beam deflection was measured as a function of applied current. In the case of the permanent magnet actuator, the experimental observations were compared with theoretical predictions.

Meso-Scale Electromagnetic Pumps Fabricated With Low-Temperature Co-Fired Ceramic Tapes and Kapton Polyimide Films

Meso-scale electromagnetically actuated reciprocating diaphragm pumps were fabricated with low-te... more Meso-scale electromagnetically actuated reciprocating diaphragm pumps were fabricated with low-temperature co-fired ceramic (LTCC) tapes and Kapton polyimide film. One design of the pump consisted of a chamber machined in LTCC substrate layers. The chamber was covered on one side with a Kapton diaphragm on which copper coils were shaped. The diaphragm was electromagnetically actuated in the presence of a permanent magnet. Passive Kapton flap valves were used to direct fluid flow into and out of the chamber. In the second pump design, the chamber was covered on both sides with Kapton diaphragms. Coils were formed on both diaphragms and current was transmitted through these coils in opposite directions and in the presence of a permanent magnet. Data for flow rate as a function of actuation frequency is presented for the first pump design. Although the pump was not optimized, flow rates on the order of a few mL per minute were recorded.

High-Throughput, Motility-Based Sorter for Microswimmers and Gene Discovery Platform

Bulletin of the American Physical Society, Nov 24, 2015

High-Throughput, Motility-Based Sorter for Microswimmers and Gene Discovery Platform 1 JINZHOU YU... more High-Throughput, Motility-Based Sorter for Microswimmers and Gene Discovery Platform 1 JINZHOU YUAN, DAVID RAIZEN, HAIM BAU, University of Pennsylvania -Animal motility varies with genotype, disease progression, aging, and environmental conditions. In many studies, it is desirable to carry out high throughput motility-based sorting to isolate rare animals for, among other things, forward genetic screens to identify genetic pathways that regulate phenotypes of interest. Many commonly used screening processes are labor-intensive, lack sensitivity, and require extensive investigator training. Here, we describe a sensitive, high throughput, automated, motility-based method for sorting nematodes. Our method was implemented in a simple microfluidic device capable of sorting many thousands of animals per hour per module, and is amenable to parallelism. The device successfully enriched for known C. elegans motility mutants. Furthermore, using this device, we isolated low-abundance mutants capable of suppressing the somnogenic effects of the flp-13 gene, which regulates sleep-like quiescence in C. elegans. Subsequent genomic sequencing led to the identification of a flp-13suppressor gene.

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Fabrication of nanoscale nozzle for electrostatic field induced inkjet head and test of drop-on-demand operation

TechConnect Briefs, Jun 1, 2008

This paper presents the fabrication of microscale to nanoscale nozzle and patterning by means of ... more This paper presents the fabrication of microscale to nanoscale nozzle and patterning by means of electrostatic field induced drop-on-demand inkjet printing system. Typically using the nanoscale nozzle we could eject nanoscale droplets and show feasibility to form patterns ranging from micro scale to nano scale on large area substrates at high speed.

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Do proximate, C. elegans swimmers synchronize their gait?

APS Division of Fluid Dynamics Meeting Abstracts, Nov 1, 2012

Capacitive Charging and Desalination with Porous Electrodes

Bulletin of the American Physical Society, Nov 24, 2013

Capacitive Charging and Desalination with Porous Electrodes HOWARD HU, MENGYING LI, HAIM BAU, Uni... more Capacitive Charging and Desalination with Porous Electrodes HOWARD HU, MENGYING LI, HAIM BAU, University of Pennsylvania -Electrochemical capacitors (ECs) are attractive storage devices with many advantages over traditional batteries. In contrast to batteries, ECs store energy in the electric double layer and do not undergo electrochemical reactions during charging and discharging. In this work, we examine the charging/discharging process of an EC cell consisting of a conductive, granular medium confined between two parallel, current collecting, electrodes. The granular particles are porous, assembled by aggregation, and saturated with an electrolyte solution. They are separated into two compartments with an ion-permeable, electrically insulating membrane. The Debye screening length around and within porous particles is small compared to the characteristic size of the pores. We will present a mathematical model based on Poisson-Nernst-Planck equations to describe the charging/discharging process in the EC cell. Using this model, the ion distribution and potential variation within the cell are solved numerically as functions of time when the current collecting electrodes are subjected to a step change and to time-periodic alternations in electrodes' potentials. The same model can be also used for potential desalination applications.

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Beam-Sample Interactions During Liquid Cell Electron Microscopy

Microscopy and Microanalysis, Aug 1, 2013

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The Polarization of Nanorods Submerged in an Electrolyte Solution and Subjected to an AC Electric Field

Bulletin of the American Physical Society, Nov 23, 2009

Recently, there has been a growing interest in utilizing electric fields to position and separate... more Recently, there has been a growing interest in utilizing electric fields to position and separate rod-shaped particles such as DNA molecules, actin filaments, and nanorods. The polarization of the electric double layer enveloping the rod plays a critical role in determining the magnitude and direction of the rod's dipole moment. We calculate the dipole moment as a function of the electric field frequency, the rod's aspect ratio (length/radius), the rod's free surface charge, and the double layer's thickness. To this end, we solve the Poisson-Nernst-Planck equations for the ions' migration, diffusion, and convection. When the surface charge is small and the rod is short, the dipole moment is negative. As the rod's length increases, the dipole moment increases, and eventually changes sign from negative to positive. The dipole coefficient of rods, whose length is greater than some critical value, increases linearly with length. The theoretical predictions are compared and favorably agree with experimental data for short DNA molecules.

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Dynamics of Sub-Micron Bubbles Growing in a Wedge in the Low Capillary Number Regime

Bulletin of the American Physical Society, Nov 24, 2014

Using a hermetically-sealed liquid cell, we observed the growth and migration of bubbles (tens to... more Using a hermetically-sealed liquid cell, we observed the growth and migration of bubbles (tens to hundreds of nanometers in diameter) with a transmission electron microscope. The internal pressure of the liquid caused the thin silicon nitride membranes that comprise the cell's observation windows to bow outward, creating spatial gradients in the liquid cell's height. As a result, growing bubbles migrated in the direction of increasing cell height. To better understand the migration dynamics, we developed a simple, two-dimensional model to predict the translational velocity of a bubble that makes contact with both wedge surfaces as a function of the bubble growth rate and wedge opening angle. The model is valid in the asymptotic limit of zero capillary number and relies on a phenomenological relationship between the contact line velocity and the dynamic contact angle. The theoretical predictions are compared with experimental observations.

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In-Situ Electron Microscopy of Electrochemical Deposition, Dendrite Growth, and Etching

Journal of heat transfer, Aug 1, 2014

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In Situ Electrochemical Measurements in the Nanoaquarium

Microscopy and Microanalysis, Aug 1, 2013

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Estimation of Nanoscale Current Density Distributions during Electrodeposition

Microscopy and Microanalysis, Aug 1, 2015

The control of interfacial morphology in electrochemical processes is essential for various appli... more The control of interfacial morphology in electrochemical processes is essential for various applications. Morphological instability, particularly dendrite formation, can cause potentially catastrophic failure in rechargeable batteries and can lower the quality of electroplated coatings, yet may also be useful in forming porous deposits. Thus, it is important to understand the temporal development of morphology and the nature of the forces that govern the geometry of the electrode-electrolyte interface. Liquid cell electron microscopy allows us to image, in real time and with nanoscale resolution, the evolution of the solid-liquid interface during electrochemical deposition as a function of process conditions [1-3]. Our nanoscale resolution allows us to infer the current density along the interface. Here, we use liquid cell electron microscopy to quantify the transient growth of interfaces during galvanostatic deposition of copper from acidic electrolytes. We extract the explicit electrode-electrolyte interface as a function of time, which gives, among other measures, the normal growth velocity at each point along the interface, a measure of the point-wise current density on a time and length scale previously inaccessible. We find that initial stages of growth can be understood through Kinetic Roughening Theory . At longer times, we identify a transition in growth mode consistent with the onset of diffusion limited growth. The non-uniform distribution of current density along the interface ultimately leads to a rapid increase in the amplitude of surface asperities .

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