Remote Manipulation of Droplets on a Flexible Magnetically Responsive Film

The manipulation of droplets is used in a wide range of applications, from lab-on-a-chip devices to bioinspired functional surfaces. Although a variety of droplet manipulation techniques have been proposed, active, fast and reversible manipulation of pure discrete droplets remains elusive due to the technical limitations of previous techniques. Here, we describe a novel technique that enables active, fast, precise and reversible control over the position and motion of a pure discrete droplet with only a permanent magnet by utilizing a magnetically responsive flexible film possessing actuating hierarchical pillars on the surface. This magnetically responsive surface shows reliable actuating capabilities with immediate field responses and maximum tilting angles of ???90??. Furthermore, the magnetic responsive film exhibits superhydrophobicity regardless of tilting angles of the actuating pillars. Using this magnetically responsive film, we demonstrate active and reversible manipulation of droplets with a remote magnetic force.open0

Ultrasensitive Detection of a Protein by Optical Trapping in a Photonic-Plasmonic Microcavity

Microcavity and whispering gallery mode (WGM) biosensors derive their sensitivity from monitoring frequency shifts induced by protein binding at sites of highly confined field intensities, where field strengths can be further amplified by excitation of plasmon resonances in nanoparticle layers. Here, we propose a mechanism based on optical trapping of a protein at the site of plasmonic field enhancements for achieving ultra sensitive detection in only microliter-scale sample volumes, and in real-time. We demonstrate femto-Molar sensitivity corresponding to a few 1000s of macromolecules. Simulations based on Mie theory agree well with the optical trapping concept at plasmonic 'hotspots' locations.Comment: submitted JBP March 2012 published JBP June 2012; Journal of Biophotonics June 2012 (online

Exhaustion of racing sperm in nature-mimicking microfluidic channels during sorting

Fertilization is central to the survival and propagation of a species, however, the precise mechanisms that regulate the sperm's journey to the egg are not well understood. In nature, the sperm has to swim through the cervical mucus, akin to a microfluidic channel. Inspired by this, a simple, cost-effective microfluidic channel is designed on the same scale. The experimental results are supported by a computational model incorporating the exhaustion time of sperm.Fil: Tasoglu, Savas. Harvard Medical School. Brigham and Women’s Hospital. Department of Medicine. Laboratory Center for Bioengineering. Bio-Acoustic-MEMS in Medicine; Estados UnidosFil: Safaee, Hooman. Harvard Medical School. Brigham and Women’s Hospital. Department of Medicine. Laboratory Center for Bioengineering. Bio-Acoustic-MEMS in Medicine; Estados UnidosFil: Zhang, Xiaohui. Harvard Medical School. Brigham and Women’s Hospital. Department of Medicine. Laboratory Center for Bioengineering. Bio-Acoustic-MEMS in Medicine; Estados UnidosFil: Kingsley, James L.. Worcester Polytechnic Institute. Department of Physics; Estados UnidosFil: Catalano, Paolo Nicolás. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Desarrollo Tecnológico y Proyectos Especiales. Departamento de Micro y Nanotecnología; Argentina. Harvard Medical School. Brigham and Women’s Hospital. Department of Medicine. Laboratory Center for Bioengineering. Bio-Acoustic-MEMS in Medicine; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gurkan, Umut Atakan. Harvard Medical School. Brigham and Women’s Hospital. Department of Medicine. Laboratory Center for Bioengineering. Bio-Acoustic-MEMS in Medicine; Estados UnidosFil: Nureddin, Aida. Harvard Medical School. Brigham and Women’s Hospital. Department of Medicine. Laboratory Center for Bioengineering. Bio-Acoustic-MEMS in Medicine; Estados UnidosFil: Kayaalp, Emre. Jamaica Hospital Medical Center. Department of Obstetrics and Gynecology; Estados UnidosFil: Anchan, Raymond M.. Harvard Medical School. Brigham and Women’s Hospital. Obstetrics Gynecology and Reproductive Biology. Center for Infertility and Reproductive Surgery ; Estados UnidosFil: Maas, Richard L.. Harvard Medical School. Brigham and Women’s Hospital. Department of Medicine. Division of Genetics; Estados UnidosFil: Tüzel, Erkan. Worcester Polytechnic Institute. Biomedical Engineering and Computer Science. Department of Physics; Estados UnidosFil: Demirci, Utkan. Harvard Medical School. Brigham and Women’s Hospital. Department of Medicine. Laboratory Center for Bioengineering. Bio-Acoustic-MEMS in Medicine; Estados Unidos. Harvard-Massachusetts Institute of Technology Health Sciences and Technology; Estados Unido

Extinction Risk in Successional Landscapes Subject to Catastrophic Disturbances

We explore the thesis that stochasticity in successional-disturbance systems can be an agent of species extinction. The analysis uses a simple model of patch dynamics for seral stages in an idealized landscape; each seral stage is assumed to support a specialist biota. The landscape as a whole is characterized by a mean patch birth rate, mean patch size, and mean lifetime for each patch type. Stochasticity takes three forms: (1) patch stochasticity is randomness in the birth times and sizes of individual patches, (2) landscape stochasticity is variation in the annual means of birth rate and size, and (3) turnover mode is whether a patch is eliminated by disturbance or by successional change. Analytical and numerical analyses of the model suggest that landscape stochasticity is the most important agent. Landscape stochasticity increases the extinction risk to species by increasing the risk that the habitat will fluctuate to zero, by reducing the mean abundance of species, and by increasing the variance in species abundance. The highest risk was found to occur in species that inhabit patches with short lifetimes. The results of this general model suggest an important mechanism by which climate change threatens biodiversity: an increase in the frequency of extreme climate events will probably cause pulses of disturbance during some time periods; these in turn would cause wider fluctuations in annual disturbance rates and thus increase the overall level of landscape stochasticity. However, the model also suggests that humans can manipulate landscape stochasticity to reduce risk. In particular, if managed disturbances were more evenly distributed in time, attrition of the regional biota might be prevented. Other work on the connection between patch dynamics and extinction risk assumes the absence of landscape stochasticity and thus overlooks an important component of risk to biodiversity

Appendix A. Solution techniques, optimal biomass densities, and dispersal flows.

Solution techniques, optimal biomass densities, and dispersal flows