Jean-Pierre Delplanque

Continuous Droplet Removal upon Dropwise Condensation of Humid Air on a Hydrophobic Micropatterned Surface

Combination of two physical phenomena, capillary pressure gradient and wettability gradient, allows a simple two-step fabrication process that yields a reliable hydrophobic self-cleaning condenser surface. The surface is fabricated with specific microscopic topography and further treatment with a chemically inert low-surface-energy material. This process does not require growth of nanofeatures (nanotubes) or hydrophilic–hydrophobic patterning of the surface. Trapezoidal geometry of the microfeatures facilitates droplet transfer from the Wenzel to the Cassie state and reduces droplet critical diameter. The geometry of the micropatterns enhances local coalescence and directional movement for droplets with diameter much smaller than the radial length of the micropatterns. The hydrophobic self-cleaning micropatterned condenser surface prevents liquid film formation and promotes continuous dropwise condensation cycle. Upon dropwise condensation, droplets follow a designed wettability gradient created with micropatterns from the most hydrophobic to the least hydrophobic end of the surface. The surface has higher condensation efficiency, due to its directional self-cleaning property, than a plain hydrophobic surface. We explain the self-actuated droplet collection mechanism on the condenser surface and demonstrate experimentally the creation of an effective wettability gradient over a 6 mm radial distance. In spite of its fabrication simplicity, the fabricated surface demonstrates self-cleaning property, enhanced condensation performance, and reliability over time. Our work enables creation of a hydrophobic condenser surface with the directional self-cleaning property that can be used for collection of biological (chemical, environmental) aerosol samples or for condensation enhancement.

Transcritical Vaporization of Liquid Fuels and Propellants

An overviewis provided of somechallenges associated with predicting spray combustion processes in propulsion systems operating at pressures and temperatures that are above the critical values of the pure fuel or propellant injected in the liquid phase (e.g., diesel engines and cryogenic liquid rocket engines). The issues determining high-pressure phase equilibria are outlined e rst. Then, the case of the gasie cation of a liquid fuel (propellant) droplet in a quiescent environment is considered. The reviewed literature shows that the more advanced models now provide consistent predictions regarding, for instance, the variation of droplet lifetime with pressure. The droplet gasie cation process at these conditions is essentially unsteady. Recent studies using molecular dynamics simulations to investigate transcritical droplet vaporization are briee y discussed. Next, the effects of convection, secondary atomization, and the proximity of neighbors on supercritical droplet combustion are considered. Published results indicate that the latter tends to preclude droplets in clouds from reaching the critical mixing state. Forced convective effects on the behavior of a droplet at supercritical conditions are considerable because they couplewith a signie cantly reduced surfacetension coefe cient to produce secondary atomization and a one order of magnitude reduction in the droplet lifetime. Finally, a specie c example is given of how supercriticality ine uences the overall performance of propulsion systems.

Personal Lung Function Monitoring Devices for Asthma Patients

Asthma affects over 300 million people worldwide. Asthmatics experience difficulty in breathing and airflow obstruction caused by inflammation and constriction of the airways. Home monitoring of lung function is the preferred course of action to give physicians and asthma patients a chance to control the disease jointly. Thus, it is important to develop accurate and efficient asthma monitoring devices that are easy for patients to use. While classic spirometry is currently the best way to capture a complete picture of airflow obstruction and lung function, the machines are bulky and generally require supervision. Portable peak flow meters are available but are inconvenient to use. There also exist no portable inexpensive exhaled breath biomarker devices commercially available to simultaneously measure concentrations of multiple chemical biomarkers. We have created a user-friendly, accurate, and portable external mobile device accessory that collects spirometry, peak expiratory flow, exhaled nitric oxide, carbon monoxide, and oxygen concentration information from patients after two breath maneuvers. We have also developed a software application that records and stores the gathered test information and e-mails the results to a physician. Telemetric capabilities help physicians to track asthma symptoms and lung function over time, which allow physicians the opportunity to make appropriate changes in a patients medication regimen more quickly.

Fully-implicit orthogonal reconstructed Discontinuous Galerkin method for fluid dynamics with phase change

A new reconstructed Discontinuous Galerkin (rDG) method, based on orthogonal basis/test functions, is developed for fluid flows on unstructured meshes. Orthogonality of basis functions is essential for enabling robust and efficient fully-implicit Newton-Krylov based time integration. The method is designed for generic partial differential equations, including transient, hyperbolic, parabolic or elliptic operators, which are attributed to many multiphysics problems. We demonstrate the methods capabilities for solving compressible fluid-solid systems (in the low Mach number limit), with phase change (melting/solidification), as motivated by applications in Additive Manufacturing (AM). We focus on the methods accuracy (in both space and time), as well as robustness and solvability of the system of linear equations involved in the linearization steps of Newton-based methods. The performance of the developed method is investigated for highly-stiff problems with melting/solidification, emphasizing the advantages from tight coupling of mass, momentum and energy conservation equations, as well as orthogonality of basis functions, which leads to better conditioning of the underlying (approximate) Jacobian matrices, and rapid convergence of the Krylov-based linear solver.

Wettability-gradient-driven micropump for transporting discrete liquid drops

In this paper, we report our efforts toward building a microelectromechanical system-based micropump. The micropump is driven by a wettability gradient and used to transport discrete drops. The gradient in wettability is distributed axisymmetrically, with hydrophobicity of the micropump surface decreasing radially toward the center. Both physical and chemical properties of the surface are altered to obtain the wettability gradient needed for driving the drops. The surface of the micropump is, first, patterned with pre-designed micro-features that define the roughness of the surface and, then, coated with a low-energy interface film. Results show that drops deposited on the surface of the micropump move, in a directional way, along the wettability gradient. The average velocity of the deposited drops is 5 mm s−1. Measured contact angles decrease gradually from 157.0° to 124.2° toward the center of the micropump surface. Maximum driving force exerted by the solid surface on the drops is 12.82 µN. The average size of the drops transported on the surface of the micropump is 2 µL.

Human breath metabolomics using an optimized non-invasive exhaled breath condensate sampler

Exhaled breath condensate (EBC) analysis is a developing field with tremendous promise to advance personalized, non-invasive health diagnostics as new analytical instrumentation platforms and detection methods are developed. Multiple commercially-available and researcher-built experimental samplers are reported in the literature. However, there is very limited information available to determine an effective breath sampling approach, especially regarding the dependence of breath sample metabolomic content on the collection device design and sampling methodology. This lack of an optimal standard procedure results in a range of reported results that are sometimes contradictory. Here, we present a design of a portable human EBC sampler optimized for collection and preservation of the rich metabolomic content of breath. The performance of the engineered device is compared to two commercially available breath collection devices: the RTube™ and TurboDECCS. A number of design and performance parameters are considered, including: condenser temperature stability during sampling, collection efficiency, condenser material choice, and saliva contamination in the collected breath samples. The significance of the biological content of breath samples, collected with each device, is evaluated with a set of mass spectrometry methods and was the primary factor for evaluating device performance. The design includes an adjustable mass-size threshold for aerodynamic filtering of saliva droplets from the breath flow. Engineering an inexpensive device that allows efficient collection of metalomic-rich breath samples is intended to aid further advancement in the field of breath analysis for non-invasive health diagnostic. EBC sampling from human volunteers was performed under UC Davis IRB protocol 63701-3 (09/30/2014-07/07/2017).

Enhanced non-invasive respiratory sampling from bottlenose dolphins for breath metabolomics measurements

Chemical analysis of exhaled breath metabolites is an emerging alternative to traditional clinical testing for many physiological conditions. The main advantage of breath analysis is its inherent non-invasive nature and ease of sample collection. Therefore, there exists a great interest in further development of this method for both humans and animals. The physiology of cetaceans is exceptionally well suited for breath analysis due to their explosive breathing behavior and respiratory tract morphology. At the present time, breath analysis in cetaceans has very limited practical applications, in large part due to lack of widely adopted sampling device(s) and methodologies that are well-standardized. Here, we present an optimized design and the operating principles of a portable apparatus for reproducible collection of exhaled breath condensate from small cetaceans, such as bottlenose dolphins (Tursiops truncatus). The device design is optimized to meet two criteria: standardized collection and preservation of information-rich metabolomic content of the biological sample, and animal comfort and ease of breath sample collection. The intent is to furnish a fully-benchmarked technology that can be widely adopted by researchers and conservationists to spur further developments of breath analysis applications for marine mammal health assessments.

Investigation of atypical molten pool dynamics in tungsten carbide-cobalt during laser deposition using in-situ thermal imaging

An atypical “swirling” phenomenon observed during the laser deposition of tungsten carbide-cobalt cermets by laser engineered net shaping (LENS®) was studied using in-situ high-speed thermal imaging. To provide fundamental insight into this phenomenon, the thermal behavior of pure cobalt during LENS was also investigated for comparison. Several factors were considered as the possible source of the observed differences. Of those, phase difference, material emissivity, momentum transfer, and free surface disruption from the powder jets, and, to a lesser extent, Marangoni convection were identified as the relevant mechanisms.

Development and Validation of a Multi-Algorithm Analytic Platform to Detect Off-Target Mechanical Ventilation

Healthcare-specific analytic software is needed to process the large volumes of streaming physiologic waveform data increasingly available from life support devices such as mechanical ventilators. Detection of clinically relevant events from these data streams will advance understanding of critical illness, enable real-time clinical decision support, and improve both clinical outcomes and patient experience. We used mechanical ventilation waveform data (VWD) as a use case to address broader issues of data access and analysis including discrimination between true events and waveform artifacts. We developed an open source data acquisition platform to acquire VWD, and a modular, multi-algorithm analytic platform (ventMAP) to enable automated detection of off-target ventilation (OTV) delivery in critically-ill patients. We tested the hypothesis that use of artifact correction logic would improve the specificity of clinical event detection without compromising sensitivity. We showed that ventMAP could accurately detect harmful forms of OTV including excessive tidal volumes and common forms of patient-ventilator asynchrony, and that artifact correction significantly improved the specificity of event detection without decreasing sensitivity. Our multi-disciplinary approach has enabled automated analysis of high-volume streaming patient waveform data for clinical and translational research, and will advance the study and management of critically ill patients requiring mechanical ventilation.

Retraction: Wettability-gradient-driven micropump for transporting discrete liquid drops

This is a Retraction for the article 2013 J. Micromech. Microeng. 23 035036. The science reported in this article is not incorrect. This article does not include all co-authors who contributed to the work. The article incorrectly attributes work performed at the University of California to the University of Jordan, and fails to acknowledge contributions from Georgia Institute of Technology. This article does not acknowledge the sources of funding for the work and the reference list is incomplete. This article was submitted by Hamzeh K Bardaweel without the knowledge of the other authors.