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2. Modulating Leidenfrost-like Prompt Jumping of Sessile Droplets on Microstructured Surfaces NPformat

Author

Huang, Wenge, Zhao, Lei, He, Yang Li Xukun, Collier, C. Patrick, Zheng, Zheng, Liu, Jiansheng, and Cheng, Dayrl P. Briggs Jiangtao

Subjects
Physics - Fluid Dynamics
Abstract

The Leidenfrost effect, namely the levitation and hovering of liquid drops on hot solid surfaces, generally requires a sufficiently high substrate temperature to activate the intense liquid vaporization. Here we report the agile modulations of Leidenfrost-like prompt jumping of sessile water microdroplets on micropillared surfaces at a remarkably mitigated temperature. Compared to traditional Leidenfrost effect occurring above 230 {\deg}C, the fin-array-like micropillars enables Wenzel-state water microdroplets to levitate and jump off within 1.33 ms at an unprecedently low temperature of 130 {\deg}C by triggering the inertia-controlled growth of individual vapor bubbles at the droplet base. We demonstrate that droplet jumping, resulting from the momentum interactions between the expanding vapor bubble and the droplet, can be deftly modulated by simply tailoring the thermal boundary layer thickness via pillar heights, which acts to regulate the bubble expansion between the inertia-controlled mode and the heat-transfer-limited mode. Intriguingly, the two bubble growth modes give rise to distinct droplet jumping behaviors characterized by constant velocity and constant energy schemes, respectively. This strategy allows the facile purging of wetting liquid drops on rough or structured surfaces in a controlled manner, inspiring promising applications in rapid removal of fouling even settled in surface cavities.

Published
2022

13. Evidence for long-term potentiation in phospholipid membranes

Author

Scott, Haden L., primary, Bolmatov, Dima, additional, Podar, Peter T., additional, Liu, Zening, additional, Kinnun, Jacob J., additional, Doughty, Benjamin, additional, Lydic, Ralph, additional, Sacci, Robert L., additional, Collier, C. Patrick, additional, and Katsaras, John, additional

Published
2022
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16. Manipulating droplet jumping behaviors on hot substrates with surface topography by controlling vapor bubble growth: from vibration to explosion

Author

Huang, Wenge, He, Xukun, Collier, C. Patrick, Zheng, Zheng, Liu, Jiansheng, and Cheng, Jiangtao

Subjects
Fluid Dynamics (physics.flu-dyn), FOS: Physical sciences, Physics - Fluid Dynamics
Abstract

A major challenge in surface science is rapid removal of sessile liquid droplets from a substrate with complex three-dimensional structures. However, our understanding of interfacial phenomena including droplet wetting dynamics and phase changes on engineered surfaces remains elusive, impeding dexterous designs for agile droplet purging. Here we present a surface topography strategy to modulate droplet jumping behaviors on micropillared substrates at moderate superheat of 20-30 {\deg}C. Specifically, sessile droplets usually dwell in the Wenzel state and therefore the micropillar matrix functions as fin array for heat transfer enhancement. By tuning the feature sizes of micropillars, one can adjust the vapor bubble growth at the droplet base from the heat-transfer-controlled mode to the inertia-controlled mode. As opposed to the relatively slow vibration jumping in seconds, the vapor bubble growth in the inertia-controlled mode on tall-micropillared surface leads to droplet out-of-plane jumping in milliseconds. Such rapid droplet detachment stems from the swift Wenzel-to Cassie transition incurred by vapor bubble burst (explosion), during which the bubble expanding velocity can reach as fast as ~4 m/s. Vapor bubble growth in a droplet and bubble-burst-induced droplet jumping have been less explored. This study unveils the underpinning mechanisms of versatile jumping behaviors of boiling droplets from a hot micro-structured surface and opens up further possibilities for the design of engineered surfaces that mitigate potential damage of vapor explosion or alleviate condensate flooding.

Published
2022

17. Heterosynaptic plasticity in biomembrane memristors controlled by pH

Author

McClintic, William T., primary, Scott, Haden L., additional, Moore, Nick, additional, Farahat, Mustafa, additional, Maxwell, Mikayla, additional, Schuman, Catherine D., additional, Bolmatov, Dima, additional, Barrera, Francisco N., additional, Katsaras, John, additional, and Collier, C. Patrick, additional

Published
2022
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19. Readers Write

Author

Scholand, Kathleen R., Solvis, Max, Collier, C. Patrick, Lenox, Caroline, Clay, Linda, Hushbeck, Joy, and Abraham, Michael

Published
2001

23. Droplet Evaporation on Hot Micro-Structured Superhydrophobic Surfaces: Analysis of Evaporation from Droplet Cap and Base Surfaces

Author

Huang, Wenge, He, Xukun, Liu, Cong, Li, Xiaojie, Liu, Yahua, Collier, C. Patrick, Srijanto, Bernadeta R., Liu, Jiansheng, and Cheng, Jiangtao

Subjects
Physics::Fluid Dynamics, 02 Physical Sciences, Physics::Atomic and Molecular Clusters, Mechanical Engineering & Transports, Physics::Atmospheric and Oceanic Physics, 01 Mathematical Sciences, 09 Engineering
Abstract

In this study, evaporation of sessile water droplets on hot micro-structured superhydrophobic surfaces is experimentally and theoretically investigated. Water droplets of 4 µL are placed on micro-pillared silicon substrates with the substrate temperature heated up to 120°C. A comprehensive thermal circuit model is developed to analyze the effects of substrate roughness and substrate temperature on the sessile droplet evaporation. For the first time, two components of heat and mass transfer, i.e., one from the droplet cap surface and the other from the droplet base surface, during droplet evaporation are distinguished and systematically studied. As such, the evaporation heat transfer rates from both the droplet cap surface and the interstitial liquid-vapor interface between micropillars at the droplet base are calculated in various conditions. For droplet evaporation on the heated substrates in the range of 40°C – 80°C, the predicted droplet cap temperature matches well with the experimental results. During the constant contact radius mode of droplet evaporation, the decrease of evaporation rate from the droplet base contributes most to the continuously decreasing overall evaporation heat transfer rate, whereas the decrease of evaporation rate from the droplet cap surface is dominant in the constant contact angle mode. The influence of internal fluid flow is considered for droplet evaporation on substrates heated above 100°C, and an effective thermal conductivity is adopted as a correction factor to account for the effect of convection heat transfer inside the droplet. Temperature differences between the droplet base and the substrate base are estimated to be about 2°C, 5°C, 8°C, 13°C and 18°C for droplet evaporation on substrates heated at 40°C, 60°C, 80°C, 100°C, and 120°C, respectively, elucidating the delayed or depressed boiling of water droplets on a heated rough surface due to evaporative cooling. Published version

Published
2022

25. Menu Collection: Problems Adapted from 'Mathematics Teaching in the Middle School'.

Author

National Council of Teachers of Mathematics, Inc., Reston, VA., Collier, C. Patrick, Collier, C. Patrick, and National Council of Teachers of Mathematics, Inc., Reston, VA.

Abstract

This collection of problems provides a resource for teachers to use in the classroom to improve the problem-solving experiences of their students. This book provides middle school teachers with some perspectives on problem solving. A framework for organizing the problem- solving experience is presented. Each phase of the problem-solving experience is described, and some questions that help to define the phases are listed as well to guide thinking. An example of a particular problem, the thought processes involved, and a list of suggestions to improve problem solving is provided. (KHR)

Published
2000

26. Geometry in the Middle School: An Exchange of Ideas and Experiences.

Author

Pateracki, Tina and Collier, C. Patrick

Abstract

Argues that geometric models should be used to analyze, interpret, and solve problems from probability, algebra, and other areas of mathematics and that geometry should have a place among the major topics of emphasis in the mathematics studies of a middle school student. Presents responses from selected teachers to some questions about geometry. (ASK)

Published
1998

29. MEDIA CLiPS

Author

Collier, C. Patrick

Published
2002

31. MEDIA CLiPS

Author

Collier, C. Patrick

Published
2001

36. Shear-driven redistribution of surfactant affects enzyme activity in well-mixed femtoliter droplets

Author

Liu, Yu, Jung, Seung-Yong, and Collier, C. Patrick

Subjects
Surface active agents -- Usage, Enzyme kinetics -- Research, Microfluidics -- Research, Chemistry
Abstract

We developed a microfluidic platform for splitting well-mixed, femtoliter-volume droplets from larger water-in-oil plugs, where the sizes of the daughter droplets were not limited by channel width. These droplets were separated from mother plugs at a microfabricated T-junction, which enabled the study of how increased confinement affected enzyme kinetics in droplets 4-10 [micro]m in diameter. Initial rates for enzyme catalysis in the mother plugs and the largest daughter drops were close to the average bulk rate, while the rates in smaller droplets decreased linearly with increasing surface to volume ratio. Rates in the smallest droplets decreased by a factor of 4 compared to the bulk rate. Traditional methods for detecting nonspecific adsorption at the water--oil interface were unable to detect evidence of enzyme adsorption, including pendant drop tensiometry, laser scanning confocal microscopy of drops containing labeled proteins in microemulsions, and epifluorescence microscopy of plugs and drops generated on-chip. We propose the slowing of enzyme reaction kinetics in the smaller droplets was the result of increased adsorption and inactivation of enzymes at the water--oil interface arising from transient interfacial shear stresses imparted on the daughter droplets as they split from the mother plugs and passed through the constricted opening of the T-junction. Such stresses are known to modulate the interfacial area and density of surfactant molecules that can passivate the interface. Bright field images of the splitting processes at the junction indicate that these stresses scaled with increasing surface to volume ratios of the droplets but were relatively insensitive to the average flow rate of plugs upstream of the junction.

Published
2009

37. Photoluminescence Enhancement, Blinking Suppression, and Improved Biexciton Quantum Yield of Single Quantum Dots in Zero Mode Waveguides

Author

Masud, Abdullah Al, primary, Arefin, S. M. Nayeem, additional, Fairooz, Fatema, additional, Fu, Xu, additional, Moonschi, Faruk, additional, Srijanto, Bernadeta R., additional, Neupane, Khaga Raj, additional, Aryal, Surya, additional, Calabro, Rosemary, additional, Kim, Doo-Young, additional, Collier, C. Patrick, additional, Chowdhury, Mustafa Habib, additional, and Richards, Christopher I., additional

Published
2021
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40. Media clips: weight loss breakthrough

Author

Collier, C. Patrick

Subjects
Mathematics -- Study and teaching, Mathematics teachers -- Methods, Education, Mathematics
Abstract

Issues concerning the practical application of mathematics in every day situations are discussed. In particular a weight/height chart appearing in the media is analysed and questions and answers provided.

Published
2001

45. Insight into the Mechanisms Driving the Self-Assembly of Functional Interfaces: Moving from Lipids to Charged Amphiphilic Oligomers

Author

Chowdhury, Azhad U., primary, Taylor, Graham J., additional, Bocharova, Vera, additional, Sacci, Robert L., additional, Luo, Yingdong, additional, McClintic, William T., additional, Ma, Ying-Zhong, additional, Sarles, Stephen A., additional, Hong, Kunlun, additional, Collier, C. Patrick, additional, and Doughty, Benjamin, additional

Published
2019
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46. READERS' DIALOGUE

Author

Hishon, Jean, Collier, C. Patrick, Porzio, Joseph A., Moberg, Ward, and Pfeifer, Glenn L.

Published
1991

50. Self-Stabilizing Transpiration in Synthetic Leaves

Author

Shi, Weiwei, primary, Vieitez, Joshua R., additional, Berrier, Austin S., additional, Roseveare, Matthew W., additional, Surinach, Daniel A., additional, Srijanto, Bernadeta R., additional, Collier, C. Patrick, additional, and Boreyko, Jonathan B., additional

Published
2019
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