Microwave Dielectric Heating of Drops in Microfluidic Devices

We present a technique to locally and rapidly heat water drops in microfluidic devices with microwave dielectric heating. Water absorbs microwave power more efficiently than polymers, glass, and oils due to its permanent molecular dipole moment that has a large dielectric loss at GHz frequencies. The relevant heat capacity of the system is a single thermally isolated picoliter drop of water and this enables very fast thermal cycling. We demonstrate microwave dielectric heating in a microfluidic device that integrates a flow-focusing drop maker, drop splitters, and metal electrodes to locally deliver microwave power from an inexpensive, commercially available 3.0 GHz source and amplifier. The temperature of the drops is measured by observing the temperature dependent fluorescence intensity of cadmium selenide nanocrystals suspended in the water drops. We demonstrate characteristic heating times as short as 15 ms to steady-state temperatures as large as 30 degrees C above the base temperature of the microfluidic device. Many common biological and chemical applications require rapid and local control of temperature, such as PCR amplification of DNA, and can benefit from this new technique.Comment: 6 pages, 4 figure

Kinematic Analysis of Prey Capture in Coastal Giant Salamanders (Dicamptodon tenebrosus)

Salamanders use a variety of techniques to capture prey that involves a combination of lingual and jaw prehension. For example, some plethodontid salamanders often use ballistic tongue projection to capture prey. Salamanders of the family Dicamptodontidae, are the largest sized terrestrial salamanders in the world which feed on a diverse array of prey items (arthropods, annelids, small mammals, and reptiles). Objectives of our study were to describe and quantify the behavior of terrestrial adult coastal giant salamanders (D. tenebrosus). While there has been much research conducted on aquatic phase D. tenebrosus, little is known about their terrestrial counterparts. Feeding bouts of three distinct prey types (e.g., crickets, earthworms, and slugs) were recorded using high-speed video (420-1000 frames/second) recorded with a Casio Exlim EX-ZR100 digital camera. For a feeding trial, salamanders were offered a prey item with forceps. Trials were repeated on separated days with each salamander (N=12) being exposed to equal ratios of prey items. Videos were analyzed for velocity of initial strike, lingual projection, lower and upper jaw prehension, and feeding success. Non-metric multi-dimensional scaling analysis indicated significant differences in feeding patterns among prey types. Lingual prehension was the prominent method of ingestion when a small prey item was offered (crickets) and the use of upper and lower mandible were used in a snapping motion with larger prey items (earthworms). Future work will incorporate different prey items, as well as examine prey preference and foraging behaviors of D. tenebrosus. Additionally some comparative analysis will be conducted using the tiger salamander (Abystoma tigrinum) and the tailed frog (Ascaphus truei) on the mechanics of prey capture in amphibian taxa

Topological Graphene Imaging and Fabrication of Devices

Engineering and Applied Science

High Voltage Dielectrophoretic and Magnetophoretic Hybrid Integrated Circuit / Microfluidic Chip

A hybrid integrated circuit (IC)/microfluidic chip is presented that independently and simultaneously traps and moves microscopic objects suspended in fluid using both electric and magnetic fields. This hybrid chip controls the location of dielectric objects, such as living cells and drops of fluid, on a 60 times 61 array of pixels that are 30 times 38 mum2 in size, each of which can be individually addressed with a 50-V peak-to-peak dc-to-10-MHz radio-frequency voltage. These high-voltage pixels produce electric fields above the chip's surface with a magnitude |oarrE| ap 1 V/ mum, resulting in strong dielectrophoresis (DEP) forces |oarrFDEP| ap 1 nN. Underneath the array of DEP pixels, there is a magnetic matrix that consists of two perpendicular sets of 60 metal wires running across the chip. Each wire can be sourced with 120 mA to trap and move magnetically susceptible objects using magnetophoresis. The DEP pixel array and magnetic matrix can be used simultaneously to apply forces to microscopic objects, such as living cells or lipid vesicles, that are tagged with magnetic nanoparticles. The capabilities of the hybrid IC/microfluidic chip demonstrated in this paper provide important building blocks for a platform for biological and chemical applications.Engineering and Applied Science

Integrated Circuit / Microfluidic Chips for Dielectric Manipulation

Engineering and Applied Science

Direct Imaging of Atomic-Scale Ripples in Few-Layer Graphene

Graphene has been touted as the prototypical two-dimensional solid of extraordinary stability and strength. However, its very existence relies on out-of-plane ripples as predicted by theory and confirmed by experiments. Evidence of the intrinsic ripples has been reported in the form of broadened diffraction spots in reciprocal space, in which all spatial information is lost. Here we show direct real-space images of the ripples in a few-layer graphene (FLG) membrane resolved at the atomic scale using monochromated aberration-corrected transmission electron microscopy (TEM). The thickness of FLG amplifies the weak local effects of the ripples, resulting in spatially varying TEM contrast that is unique up to inversion symmetry. We compare the characteristic TEM contrast with simulated images based on accurate first-principles calculations of the scattering potential. Our results characterize the ripples in real space and suggest that such features are likely common in ultrathin materials, even in the nanometer-thickness range.Engineering and Applied SciencesPhysic

Microwave dielectric heating of non-aqueous droplets in a microfluidic device for nanoparticle synthesis

We describe a microfluidic device with an integrated microwave heater specifically designed to dielectrically heat non-aqueous droplets using time-varying electrical fields with the frequency range between 700 and 900 MHz. The precise control of frequency, power, temperature and duration of the applied field opens up new vistas for experiments not attainable by conventional microwave heating. We use a non-contact temperature measurement system based on fluorescence to directly determine the temperature inside a single droplet. The maximum temperature achieved of the droplets is 50 °C in 15 ms which represents an increase of about 25 °C above the base temperature of the continuous phase. In addition we use an infrared camera to monitor the thermal characteristics of the device allowing us to ensure that heating is exclusively due to the dielectric heating and not due to other effects like non-dielectric losses due to electrode or contact imperfection. This is crucial for illustrating the potential of dielectric heating of benzyl alcohol droplets for the synthesis of metal oxides. We demonstrate the utility of this technology for metal oxide nanoparticle synthesis, achieving crystallization of tungsten oxide nanoparticles and remarkable microstructure, with a reaction time of 64 ms, a substantial improvement over conventional heating methods.Engineering and Applied SciencesPhysic

Clonal architecture of secondary acute myeloid leukemia

BACKGROUND: The myelodysplastic syndromes are a group of hematologic disorders that often evolve into secondary acute myeloid leukemia (AML). The genetic changes that underlie progression from the myelodysplastic syndromes to secondary AML are not well understood. METHODS: We performed whole-genome sequencing of seven paired samples of skin and bone marrow in seven subjects with secondary AML to identify somatic mutations specific to secondary AML. We then genotyped a bone marrow sample obtained during the antecedent myelodysplastic-syndrome stage from each subject to determine the presence or absence of the specific somatic mutations. We identified recurrent mutations in coding genes and defined the clonal architecture of each pair of samples from the myelodysplastic-syndrome stage and the secondary-AML stage, using the allele burden of hundreds of mutations. RESULTS: Approximately 85% of bone marrow cells were clonal in the myelodysplastic-syndrome and secondary-AML samples, regardless of the myeloblast count. The secondary-AML samples contained mutations in 11 recurrently mutated genes, including 4 genes that have not been previously implicated in the myelodysplastic syndromes or AML. In every case, progression to acute leukemia was defined by the persistence of an antecedent founding clone containing 182 to 660 somatic mutations and the outgrowth or emergence of at least one subclone, harboring dozens to hundreds of new mutations. All founding clones and subclones contained at least one mutation in a coding gene. CONCLUSIONS: Nearly all the bone marrow cells in patients with myelodysplastic syndromes and secondary AML are clonally derived. Genetic evolution of secondary AML is a dynamic process shaped by multiple cycles of mutation acquisition and clonal selection. Recurrent gene mutations are found in both founding clones and daughter subclones. (Funded by the National Institutes of Health and others.

Genomic landscape of TP53-mutated myeloid malignancies

TP53-mutated myeloid malignancies are associated with complex cytogenetics and extensive structural variants, which complicates detailed genomic analysis by conventional clinical techniques. We performed whole-genome sequencing (WGS) of 42 acute myeloid leukemia (AML)/myelodysplastic syndromes (MDS) cases with paired normal tissue to better characterize the genomic landscape of TP53-mutated AML/MDS. WGS accurately determines TP53 allele status, a key prognostic factor, resulting in the reclassification of 12% of cases from monoallelic to multihit. Although aneuploidy and chromothripsis are shared with most TP53-mutated cancers, the specific chromosome abnormalities are distinct to each cancer type, suggesting a dependence on the tissue of origin. ETV6 expression is reduced in nearly all cases of TP53-mutated AML/MDS, either through gene deletion or presumed epigenetic silencing. Within the AML cohort, mutations of NF1 are highly enriched, with deletions of 1 copy of NF1 present in 45% of cases and biallelic mutations in 17%. Telomere content is increased in TP53-mutated AMLs compared with other AML subtypes, and abnormal telomeric sequences were detected in the interstitial regions of chromosomes. These data highlight the unique features of TP53-mutated myeloid malignancies, including the high frequency of chromothripsis and structural variation, the frequent involvement of unique genes (including NF1 and ETV6) as cooperating events, and evidence for altered telomere maintenance