Micro-Object Manipulation Using Oscillating Bubbles

This thesis deals with the development of novel manipulation techniques of micro/mini objects using oscillating bubbles. Two major physical principles studied and applied are cavitational microstreaming flows and electrowetting on dielectric (EWOD) actuation in gaseous bubbles. Micro/mini bubbles oscillated and handled in 2-D and 3-D spaces using these two principles are key components serving as carriers of objects to be manipulated. The first type of manipulation system allows us to manipulate mini/micro objects on a 2-D space. A series of bubble operations (creation, elimination, and transportation) and object manipulations (capturing, carrying, and releasing) is extensively investigated in this configuration along with modeling and analysis. The capturing force is identified and completely confirmed as the acoustic radiation force through several experiments. Effects of the frequency and amplitude of acoustic excitation on capturing are quantified with high-speed imaging. The bubble elimination process is modeled by two sequential steps: catalytic reaction and dissolving process.In addition, the similar operations of capturing, carrying, releasing of objects are accomplished only using AC-EWOD, not using the acoustic excitation. In this case, the AC voltage (optimal frequency of 100 Hz) not only oscillates the bubble but also transports the oscillating bubble on the surface. However, the carrying efficiency is lower than the simultaneous actuations of acoustic excitation and EWOD. The second type of object manipulation system utilizes the capturing phenomenon by oscillating bubble. The main feature is that the oscillating bubble is deposited on a 3-D traversing rod tip, rather than a two-dimensional surface. So, it allows for object manipulation in a 3-D space. It is concluded from multiple experiments that the maximum carrying speed is highest near the bubble resonant frequency, meaning that the capturing force is proportional to the bubble oscillation amplitude.Finally, the cavitational streaming flow is extended to underwater propulsion. The key concept is to utilize the net momentum flux around the oscillating bubble. As a reaction force, the net momentum flux pushes or pulls the solid substrate on which the oscillating bubble sits. Using mini/micro glass rods, the propulsion mechanism is experimentally proved. The propulsion force is measured to be hundreds of nano-Newtons in a pendulum configuration

Whole-genome, transcriptome, and methylome analyses provide insights into the evolution of platycoside biosynthesis in Platycodon grandiflorus, a medicinal plant

Triterpenoid saponins (TSs) are common plant defense phytochemicals with potential pharmaceutical properties. Platycodon grandiflorus (Campanulaceae) has been traditionally used to treat bronchitis and asthma in East Asia. The oleanane-type TSs, platycosides, are a major component of the P. grandiflorus root extract. Recent studies show that platycosides exhibit anti-inflammatory, antiobesity, anticancer, antiviral, and antiallergy properties. However, the evolutionary history of platycoside biosynthesis genes remains unknown. In this study, we sequenced the genome of P. grandiflorus and investigated the genes involved in platycoside biosynthesis. The draft genome of P. grandiflorus is 680.1Mb long and contains 40,017 protein-coding genes. Genomic analysis revealed that the CYP716 family genes play a major role in platycoside oxidation. The CYP716 gene family of P. grandiflorus was much larger than that of other Asterid species. Orthologous gene annotation also revealed the expansion of beta -amyrin synthases (bASs) in P. grandiflorus, which was confirmed by tissue-specific gene expression. In these expanded gene families, we identified key genes showing preferential expression in roots and association with platycoside biosynthesis. In addition, whole-genome bisulfite sequencing showed that CYP716 and bAS genes are hypomethylated in P. grandiflorus, suggesting that epigenetic modification of these two gene families affects platycoside biosynthesis. Thus whole-genome, transcriptome, and methylome data of P. grandiflorus provide novel insights into the regulation of platycoside biosynthesis by CYP716 and bAS gene families

Acoustic wave-driven oxide dependant dynamic behavior of liquid metal droplet for inkjet applications

In this paper, we report bouncing and separating dynamic behaviors of a liquid metal droplet with/without the oxide layer in response to the applied acoustic wave. The oxidized liquid metal droplet is readily bounced off from the surface when it is excited by acoustic wave, while the HCl treated liquid metal droplet is fragmented into several small droplets. The bouncing height of the oxidized liquid metal is proportional to the applied acoustic wave amplitude. The number of the fragmented liquid metal droplets for the HCl-treated liquid metal according to time and acoustic wave amplitude was investigated. We also demonstrated the acoustic wave-based inkjet application to generate liquid metal droplets based on the pinch-off and the Rayleigh instability by changing amplitude of the acoustic wave. The probability for the generation of various droplet sizes with different acoustic wave amplitude was also studied

Frequency tunable liquid metal on paper microstrip patch antenna

We report a liquid metal microstrip antenna on a printing paper whose resonant frequency was tunable by folding the paper. The gallium-based alloy was used as liquid metal, which is instantly oxidized in ambient air. The oxidized liquid metal is easily wettable on printing paper surfaces, while it is non-wettable on laser-printed toner surfaces. An antenna with a 3 mm wide and 39 mm long copper-liquid metal overlapped-feedline linked to the liquid metal microstrip rectangle-shaped patch (40 × 31 mm2) was designed. The antenna pattern was printed on a printing paper using a laser printer. A liquid metal soaked roller was rolled on the antenna pattern printed paper, resulting in a liquid metal pattern where there was no toner. The resonant frequency of the liquid metal on the paper microstrip patch antenna was 2.88 GHz with −18.5 dB S11. The measured characteristics of the antenna were in good agreement with the simulation results. When the antenna was folded, the resonant frequency was changed to 2.68 GHz (x-axis folding) or 2.72 GHz (y-axis folding). Liquid metal on paper fabrication is simple but effective for creating custom-designed antennas that are easily re-designed and fabricated in the field

Acoustic wave-driven oxidized liquid metal-based energy harvester

We report an oxidized liquid metal droplet-based energy harvester that converts acoustic energy into electrical energy by modulating an electrical double layer that originates from the deformation of the oxidized liquid metal droplet. Gallium-based liquid metal alloy has been developed for various applications owing to the outstanding material properties, such as its high electrical conductivity (metallic property) and unlimited deformability (liquid property). In this study, we demonstrated energy harvesting using an electrical double layer between the acoustic wave-modulated liquid metal droplet and two electrodes. The proposed energy harvester consisted of top and bottom electrodes covered with the dielectric layer and a Gallium-based liquid metal droplet placed between the electrodes. When we applied an external bias voltage and acoustic wave to the proposed device, the contact area between the liquid metal droplet and the electrodes changed, leading to the variation of the capacitance in the electrical double layer and the generation of electrical output current. Using the proposed energy harvester, the maximum output current of 41.2 nA was generated with an applied acoustic wave of 30 Hz. In addition, we studied the relationships between the maximum output current and a variety of factors, such as the size of the liquid metal droplet, the thickness of the hydrophobic layer, and the distance between the top and bottom electrode plates

Fast Electrically Driven Capillary Rise Using Overdrive Voltage

Enhancement of response speed (or reduction of response time) is crucial for the commercialization of devices based on electrowetting (EW), such as liquid lenses and reflective displays, and presents one of the main challenges in EW research studies. We demonstrate here that an overdrive EW actuation gives rise to a faster rise of a liquid column between parallel electrodes, compared to a DC EW actuation. Here, DC actuation is actually a simple applied step function, and overdrive is an applied step followed by reduction to a lower voltage. Transient behaviors and response time (i.e., the time required to reach the equilibrium height) of the rising liquid column are explored under different DC and overdrive EW actuations. When the liquid column rises up to a target height by means of an overdrive EW, the response time is reduced to as low as 1/6 of the response time using DC EW. We develop a theoretical model to simulate the EW-driven capillary rise by combining the kinetic equation of capillary flow (i.e., Lucas-Washburn equation) and the dynamic contact angle model considering contact line friction, contact angle hysteresis, contact angle saturation, and the EW effect. This theoretical model accurately predicts the outcome to within a 5% error in regard to the rising behaviors of the liquid column with a low viscosity, under both DC EW and overdrive actuation conditions, except for the early stage (<about 20 ms).1165sciescopu

C. elegans-on-a-chip for in situ and in vivo Ag nanoparticles’ uptake and toxicity assay

Photograph used for a story in the Oklahoma City Times newspaper. Caption: "Well on its way To Complettion is the new Civic Center Music Hall scheduled to open January 23 and 24 with concertesby the Oklahoma City Symphony. This is the rear portion of the hall where the first of the 3,200 seats are now being installed. The one balcony is visible as are the new wood side walls and the new ceiling. The seats will be covered with a lipstick red fabric carpeting will be gold and the wall are a walnut stain.

On-demand frequency tunability of fluidic antenna implemented with gallium-based liquid metal alloy

We investigated frequency tunability of a microfluidic-based antenna using on-demand manipulation of a gallium-based liquid metal alloy. The fluidic antenna was fabricated by polydimethylsiloxane (PDMS) and filled with the gallium-based liquid metal alloy (Galinstan®). It is composed of a digital number “7”-shaped feedline, and a square-shaped and a digital number “6”-shaped patterns, which are all implemented with the liquid metal. The gallium-based liquid metal was adhered to the channel surface due to its viscous oxide layer originating from the gallium oxide forming when it exposed to the air environment. We treated the liquid metal with hydrochloric acid solution to remove the oxide layer on the surface resulting in easy movement of the liquid metal in the channel, as the liquid metal surface has been transformed to be non-wettable. We controlled the physical length of the liquid metal slug filled in feedline with an applied air pressure, resulting in tuning the resonant frequency ranging from 2.2 GHz to 9.3 GHz. The fluidic antenna properties using the liquid metal’s electrical conductivity and mobility were characterized by measuring the return loss (S11), and also simulated with CST Microwave Studio