@article {1588433,
	title = {The Soft Framework of the Cellular Machine },
	journal = {PNAS},
	volume = {105},
	number = {4},
	year = {2008},
	pages = {1105-1106},
	abstract = {
	The mechanical properties of cells are essential in determining a myriad of functions, from mitosis to locomotion. The functional rigidity of a cell is usually thought to result from three interpenetrating networks of filamentous biopolymers: actin microfilaments, microtubules, and intermediate filaments (IF). The mechanical properties of both filamentous actin (F-actin) and microtubule networks have been extensively studied, both directly in cells and in model\&nbsp;in vitro\&nbsp;systems, consisting of reconstituted networks of purified proteins. The assembly and structures of actin and tubulin polymers, coupled to ATP and GTP hydrolysis, respectively, give rise to fascinating dynamics that have attracted experimentalists, theorists, and modelers for decades, trying to understand their properties and functions. In addition, the diverse molecular motors that run along these tracks are central to much of cell dynamics and vesicle transport. By contrast, intermediate filaments do not hydrolyze nucleotides, do not exhibit structural polarity, and have no motors that run along them. Also, unlike actin and tubulin, which exist in very similar forms in nearly all eukaryotic cells, IF proteins appeared later in evolution and mutated rapidly to form distinct molecular species in different cell types. Some classes of IFs can be genetically ablated in mice without the mice necessarily losing viability and resulting in some cases in a barely discernable phenotype. However, the IFs expressed in epithelial cells, keratin IFs (or KIFs), are required for normal epithelial function, and mutations in these proteins can cause devastating human diseases. In an article in a recent issue of PNAS, Sivaramakrishnan\&nbsp;et al.\&nbsp;reported on the results of a remarkable study of the micromechanical properties of IF networks that should begin to redress our imbalance in understanding of the mechanics of the different biopolymer networks. These authors show that the KIF networks are essential for the mechanical integrity of the cell, and without them, cells such as alveolar epithelial cells would be helpless to withstand the forces they experience as the lung inflates and stretches them.

},
	url = {https://www.pnas.org/content/105/4/1105},
	author = {Weitz, DavidA. and Paul A. Janmey}
}
@article {156441,
	title = {Gelation as arrested phase separation in short-ranged attractive colloid-polymer mixtures},
	journal = {Journal of Physics-Condensed Matter},
	volume = {20},
	number = {49},
	year = {2008},
	pages = {494242},
	abstract = {We present further evidence that gelation is an arrested phase separation in attractive colloid-polymer mixtures, based on a method combining confocal microscopy experiments with numerical simulations recently established in Lu et al (2008 Nature 453 499). Our results are independent of the form of the interparticle attractive potential and therefore should apply broadly to any attractive particle system with short-ranged, isotropic attractions. We also give additional characterization of the gel states in terms of their structure, inhomogeneous character and local density.},
	url = {https://iopscience.iop.org/article/10.1088/0953-8984/20/49/494242},
	author = {Zaccarelli, Emanuela and Lu, Peter J. and Ciulla, Fabio and Weitz, David A and Sciortino, Francesco}
}
@article {156386,
	title = {Dynamics of drying in 3D porous media},
	journal = {Physical Review Letters},
	volume = {101},
	number = {9},
	year = {2008},
	pages = {094502},
	abstract = {The drying dynamics in three dimensional porous media are studied with confocal microscopy. We observe abrupt air invasions in size from single particle to hundreds of particles. We show that these result from the strong flow from menisci in large pores to menisci in small pores during drying. This flow causes air invasions to start in large menisci and subsequently spread throughout the entire system. We measure the size and structure of the air invasions and show that they are in accord with invasion percolation. By varying the particle size and contact angle we unambiguously demonstrate that capillary pressure dominates the drying process.},
	url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.101.094502},
	author = {Xu, Lei and Davies, Simon and Schofield, Andrew B. and Weitz, David A}
}
@article {156411,
	title = {Probing nonlinear rheology with inertio-elastic oscillations},
	journal = {Journal of Rheology},
	volume = {52},
	number = {4},
	year = {2008},
	pages = {1013-1025},
	abstract = {Many common materials display significant nonlinear theological properties. Characterizing these properties can be done with a variety of methods. One such method uses inertio-elastic oscillations, which occur naturally in rotational rheometry as a consequence of a material{\textquoteright}s elasticity and the inertia of the rheometer. These oscillations have primarily been used to characterize linear viscoelastic properties. In addition to allowing for the imposition of stress-biased oscillations on short time scales, we demonstrate that extending this technique to nonlinear deformations provides accurate measurements of nonlinear material properties. Our experiments are performed on fibrin networks, which are well characterized and have dramatic nonlinear properties that are biologically significant. We compare the tangent moduli measurements of inertio-elastic oscillations with three standard methods of nonlinear rheology: forced oscillations about a prestress, a geometric interpretation of large amplitude oscillatory shears, and an extension of the linear viscoelastic moduli to the nonlinear regime. Inertio-elastic oscillations provide an accurate characterization of fibrin{\textquoteright}s nonlinear properties, and further, our measurements suggest that inertio-elastic oscillations provide the most straightforward method of distinguishing between nonlinear elasticity and dissipation at any given stress. In fact, we find that inertio-elastic oscillations provide the most accurate measurement of the subdominant loss component of our networks. (C) 2008 The Society of Rheology.},
	url = {https://sor.scitation.org/doi/10.1122/1.2933171},
	author = {Yao, Norman Y. and Larsen, RyanJ. and Weitz, David A}
}
@article {156106,
	title = {Dynamic viscoelasticity of actin cross-linked with wild-type and disease-causing mutant alpha-actinin-4},
	journal = {Biophysical Journal},
	volume = {95},
	number = {10},
	year = {2008},
	pages = {4915-4923},
	abstract = {The actin cross-linker alpha-actinin-4 has been found to be indispensable for the structural and functional integrity of podocytes; deficiency or alteration of this protein due to mutations results in kidney disease. To gain insight into the effect of the cross-linker on cytoskeletal mechanics, we studied the macroscopic rheological properties of actin networks cross-linked with wild-type and mutant alpha-actinin-4. The frequency-dependent viscoelasticity of the networks is characterized by an elastic plateau at intermediate frequencies, and relaxation toward fluid properties at low frequencies. The relaxation frequencies of networks with mutant alpha-actinin-4 are an order of magnitude lower than that with the wild-type, suggesting a slower reaction rate for the dissociation of actin and alpha-actinin for the mutant, consistent with a smaller observed equilibrium dissociation constant. This difference can be attributed to an additional binding site that is exposed as a result of the mutation, and can be interpreted as a difference in binding energy barriers. This is further supported by the Arrhenius-like temperature dependence of the relaxation frequencies.},
	url = {https://www.cell.com/biophysj/fulltext/S0006-3495(08)78630-2},
	author = {Ward, Sabine M. Volkmer and Weins, Astrid and Pollak, Martin R. and Weitz, David A}
}
@article {156006,
	title = {Absolute instability of a liquid jet in a coflowing stream},
	journal = {Physical Review Letters},
	volume = {100},
	number = {1-11},
	year = {2008},
	pages = {014502},
	abstract = {Cylindrical liquid jets are inherently unstable and eventually break into drops due to the Rayleigh-Plateau instability, characterized by the growth of disturbances that are either convective or absolute in nature. Convective instabilities grow in amplitude as they are swept along by the flow, while absolute instabilities are disturbances that grow at a fixed spatial location. Liquid jets are nearly always convectively unstable. Here we show that two-phase jets can breakup due to an absolute instability that depends on the capillary number of the outer liquid, provided the Weber number of the inner liquid is \&gt;O(1). We verify our experimental observations with a linear stability analysis.},
	url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.100.014502},
	author = {Utada, Andrew S. and Fernandez-Nieves, Alberto and Gordillo, Jose M. and Weitz, David A}
}
@article {155951,
	title = {Velocity fluctuations in a low-Reynolds-number fluidized bed},
	journal = {Journal of Fluid Mechanics},
	volume = {596},
	year = {2008},
	pages = {467-475},
	abstract = {The velocity fluctuations of particles in a low-Reynolds-number fluidized bed have important similarities and differences with the velocity fluctuations in a low-Reynolds-number sedimenting suspension. We show that, like sedimentation, the velocity fluctuations in a fluidized bed are described well by the balance between density fluctuations due to Poisson statistics and Stokes drag. However, unlike sedimentation, the correlation length of the fluctuations in a fluidized bed increases with volume fraction. We argue that this difference arises because the relaxation time of density fluctuations is completely different in the two systems.},
	url = {https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/abs/velocity-fluctuations-in-a-lowreynoldsnumber-fluidized-bed/5A280E33218CBC907AB25DCC4A45F115},
	author = {Tee, Shang-You and Mucha, P. J. and Brenner, M.P. and Weitz, D. A.}
}
@article {155886,
	title = {An algorithm for extracting the network geometry of three-dimensional collagen gels},
	journal = {Journal of Microscopy},
	volume = {232},
	number = {3},
	year = {2008},
	pages = {463-475},
	abstract = {The geometric structure of a biopolymer network impacts its mechanical and biological properties. In this paper, we develop an algorithm for extracting the network architecture of three-dimensional (3d) fluorescently labeled collagen gels, building on the initial work of Wu et al., (2003). Using artificially generated images, the network extraction algorithm is then validated for its ability to reconstruct the correct bulk properties of the network, including fiber length, persistence length, cross-link density, and shear modulus.},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2818.2008.02141.x},
	author = {Stein, Andrew M. and Vader, David A. and Jawerth, Louise M. and Weitz, David A and Sander, Leonard M.}
}
@article {155841,
	title = {Double emulsion templated monodisperse phospholipid vesicles},
	journal = {Langmuir},
	volume = {24},
	number = {15},
	year = {2008},
	pages = {7651-7653},
	abstract = {We present a novel approach for fabricating monodisperse phospholipid vesicles with high encapsulation efficiency using controlled double emulsions as templates. Glass-capillary microfluidics is used to generate monodisperse double emulsion templates. We show that the high uniformity in size and shape of the templates are maintained in the final phospholipid vesicles after a solvent removal step. Our simple and versatile technique is applicable to a wide range of phospholipids.},
	url = {https://pubs.acs.org/doi/10.1021/la801833a},
	author = {Shum, Ho Cheung and Lee, Daeyeon and Yoon, Insun and Kodger, Tom and Weitz, David A}
}
@article {155836,
	title = {Microfluidic fabrication of monodisperse biocompatible and biodegradable polymersomes with controlled permeability},
	journal = {Journal of the American Chemical Society},
	volume = {130},
	number = {29},
	year = {2008},
	pages = {9543-9549},
	abstract = {We describe a versatile technique for fabricating monodisperse polymersomes with biocompatible and biodegradable diblock copolymers for efficient encapsulation of actives. We use double emulsion as a template for the assembly of amphiphilic diblock copolymers into vesicle structures. These polymersomes can be used to encapsulate small hydrophilic solutes. When triggered by an osmotic shock, the polymersomes break and release the solutes, providing a simple and effective release mechanism. The technique can also be applied to diblock copolymers with different hydrophilic-to-hydrophobic block ratios, or mixtures of diblock copolymers and hydrophobic homopolymers. The ability to make polymer vesicles with copolymers of different block ratios and to incorporate different homopolymers into the polymersomes will allow the tuning of polymersome properties for specific technological applications.},
	url = {https://pubs.acs.org/doi/10.1021/ja802157y},
	author = {Shum, Ho Cheung and Kim, Jin-Woong and Weitz, David A}
}
@article {155801,
	title = {Designer emulsions using microfluidics},
	journal = {Materials Today},
	volume = {11},
	number = {4},
	year = {2008},
	pages = {18-27},
	abstract = {We describe new developments for the controlled fabrication of monodisperse emulsions using microfluidics. We use glass capillary devices to generate single, double, and higher order emulsions with exceptional precision. These emulsions can serve as ideal templates for generating well-defined particles and functional vesicles. Polydimethylsiloxane microfluidic devices are also used to generate picoliter-scale water-in-oil emulsions at rates as high as 10 000 drops per second. These emulsions have great potential as individual microvessels in high-throughput screening applications, where each drop serves to encapsulate single cells, genes, or reactants.},
	url = {https://www.sciencedirect.com/science/article/pii/S1369702108700531?via\%3Dihub},
	author = {Shah, Rhutesh K. and Shum, Ho Cheung and Rowat, Amy C. and Lee, Daeyeon and Agresti, Jeremy J. and Utada, Andrew S. and Chu, Liang-Yin and Kim, Jin-Woong and Fernandez-Nieves, Alberto and Martinez, Carlos J. and Weitz, David A}
}
@article {155786,
	title = {Fabrication of monodisperse thermosensitive microgels and gel capsules in microfluidic devices},
	journal = {Soft Matter},
	volume = {4},
	number = {12},
	year = {2008},
	pages = {2303-2309},
	abstract = {We use droplet-based microfluidic techniques to produce monodisperse poly( N-isopropylacrylamide) gel particles in the size range of 10-1000 mu m. Our techniques offer exquisite control over both outer dimensions and inner morphology of the particles. We demonstrate this control by fabricating conventional microgels, microgels with embedded materials and voids, and gel microcapsules with single- and multi-phase cores. These techniques should be applicable for the synthesis of particles and capsules of a variety of chemical compositions and for the generation of higher order "supraparticles{\textquoteright}{\textquoteright} by directed assembly of colloidal particles in droplets.},
	url = {https://pubs.rsc.org/en/content/articlelanding/2008/sm/b808653m$\#$!divAbstract},
	author = {Shah, Rhutesh K. and Kim, Jin-Woong and Agresti, Jeremy J. and Weitz, David A and Chu, Liang-Yin}
}
@article {155416,
	title = {Highly anisotropic vorticity aligned structures in a shear thickening attractive colloidal system},
	journal = {Soft Matter},
	volume = {4},
	number = {7},
	year = {2008},
	pages = {1388-1392},
	abstract = {Vorticity aligned cylindrical flocs of carbon black particles are formed in steady flow at low shear rates and, strikingly, appear as transient structures in the flow response of gels produced by the quenching of high rate shear thickening flows.},
	url = {https://pubs.rsc.org/en/content/articlelanding/2008/SM/b716324j$\#$!divAbstract},
	author = {Osuji, Chinedum O. and Weitz, David A}
}
@article {155401,
	title = {Optimal vein density in artificial and real leaves},
	journal = {PNAS},
	volume = {105},
	number = {27},
	year = {2008},
	pages = {9140-9144},
	abstract = {The long evolution of vascular plants has resulted in a tremendous variety of natural networks responsible for the evaporatively driven transport of water. Nevertheless, little is known about the physical principles that constrain vascular architecture. Inspired by plant leaves, we used microfluidic devices consisting of simple parallel channel networks in a polymeric material layer, permeable to water, to study the mechanisms of and the limits to evaporation-driven flow. We show that the flow rate through our biomimetic leaves increases linearly with channel density (1/d) until the distance between channels (d) is comparable with the thickness of the polymer layer (5), above which the flow rate saturates. A comparison with the plant vascular networks shows that the same optimization criterion can be used to describe the placement of veins in leaves. These scaling relations for evaporatively driven flow through simple networks reveal basic design principles for the engineering of evaporation-permeation-driven devices, and highlight the role of physical constraints on the biological design or leaves.},
	url = {https://www.pnas.org/content/105/27/9140},
	author = {Noblin, X. and Mahadevan, L and Coomaraswamy, I. A. and Weitz, D. A. and Holbrook, N. M. and Zwieniecki, M. A.}
}
@article {155406,
	title = {Shear thickening and scaling of the elastic modulus in a fractal colloidal system with attractive interactions},
	journal = {Physical Review E},
	volume = {77},
	number = {6},
	year = {2008},
	pages = {060402},
	abstract = {Dilute oil dispersions of fractal carbon black particles with attractive van der Waals interactions display continuous shear thickening followed by shear thinning at high shear rates. The shear thickening transition occurs at (gamma) over dot(c)approximate to 10(2)-10(3) s(-1) and is driven by hydrodynamic breakup of clusters. Pre-shearing dispersions at shear rates (gamma) over dot\&gt;(gamma) over dot(c) produces enhanced-modulus gels where G{\textquoteright}similar to sigma(1.5-2)(pre-shear) and is directly proportional to the residual stress in the gel measured at a fixed sample age. The observed data can be accounted for using a simple scaling model for the breakup of fractal clusters under shear stress.},
	url = {https://journals.aps.org/pre/abstract/10.1103/PhysRevE.77.060402},
	author = {Osuji, Chinedum O. and Kim, Chanjoong and Weitz, David A}
}
@article {155321,
	title = {Robust pore size analysis of filamentous networks from three-dimensional confocal microscopy},
	journal = {Biophysical Journal},
	volume = {95},
	number = {12},
	year = {2008},
	pages = {6072-6080},
	abstract = {We describe a robust method for determining morphological properties of. lamentous biopolymer networks, such as collagen or other connective tissue matrices, from confocal microscopy image stacks. Morphological properties including pore size distributions and percolation thresholds are important for transport processes, e. g., particle diffusion or cell migration through the extracellular matrix. The method is applied to fluorescently labeled fiber networks prepared from rat-tail tendon and calf-skin collagen, at concentrations of 1.2, 1.6, and 2.4 mg/ml. The collagen fibers form an entangled and branched network. The medial axes, or skeletons, representing the collagen fibers are extracted from the image stack by threshold intensity segmentation and distance-ordered homotopic thinning. The size of the fiuid pores as defined by the radii of largest spheres that fit into the cavities between the collagen fibers is derived from Euclidean distance maps and maximal covering radius transforms of the fluid phase. The size of the largest sphere that can traverse the fluid phase between the collagen fibers across the entire probe, called the percolation threshold, was computed for both horizontal and vertical directions. We demonstrate that by representing the fibers as the medial axis the derived morphological network properties are both robust against changes of the value of the segmentation threshold intensity and robust to problems associated with the point-spread function of the imaging system. We also provide empirical support for a recent claim that the percolation threshold of a fiber network is close to the fiber diameter for which the Euler index of the networks becomes zero.},
	url = {https://www.cell.com/biophysj/fulltext/S0006-3495(08)82021-8},
	author = {Mickel, Walter and Muenster, Stefan and Jawerth, Louise M. and Vader, David A. and Weitz, David A and Sheppard, Adrian P. and Mecke, Klaus and Fabry, Ben and Schroeder-Turk, Gerd E.}
}
@article {155196,
	title = {Gelation of particles with short-range attraction},
	journal = {Nature},
	volume = {453},
	year = {2008},
	pages = {499-U4},
	abstract = {Nanoscale or colloidal particles are important in many realms of science and technology. They can dramatically change the properties of materials, imparting solid-like behaviour to a wide variety of complex fluids(1,2). This behaviour arises when particles aggregate to form mesoscopic clusters and networks. The essential component leading to aggregation is an interparticle attraction, which can be generated by many physical and chemical mechanisms. In the limit of irreversible aggregation, infinitely strong interparticle bonds lead to diffusion-limited cluster aggregation(3) (DLCA). This is understood as a purely kinetic phenomenon that can form solid-like gels at arbitrarily low particle volume fraction(4,5). Far more important technologically are systems with weaker attractions, where gel formation requires higher volume fractions. Numerous scenarios for gelation have been proposed, including DLCA(6), kinetic or dynamic arrest(4,7-10), phase separation(5,6,11-16), percolation(4,12,17,18) and jamming(8). No consensus has emerged and, despite its ubiquity and significance, gelation is far from understood-even the location of the gelation phase boundary is not agreed on(5). Here we report experiments showing that gelation of spherical particles with isotropic, short-range attractions is initiated by spinodal decomposition; this thermodynamic instability triggers the formation of density fluctuations, leading to spanning clusters that dynamically arrest to create a gel. This simple picture of gelation does not depend on microscopic system-specific details, and should thus apply broadly to any particle system with short- range attractions. Our results suggest that gelation-often considered a purely kinetic phenomenon(4,8-10)-is in fact a direct consequence of equilibrium liquid gas phase separation(5,13-15). Without exception, we observe gelation in all of our samples predicted by theory and simulation to phaseseparate; this suggests that it is phase separation, not percolation(12), that corresponds to gelation in models for attractive spheres.},
	url = {https://www.nature.com/articles/nature06931},
	author = {Lu, Peter J. and Zaccarelli, Emanuela and Ciulla, Fabio and Schofield, Andrew B. and Sciortino, Francesco and Weitz, David A}
}
@article {154996,
	title = {Double emulsion-templated nanoparticle colloidosomes with selective permeability},
	journal = {Advanced Materials},
	volume = {20},
	number = {18},
	year = {2008},
	pages = {3498-3503},
	abstract = {Nanoparticle colloidosomes, shown in the SEM image, are generated by using water-in-oil-in-water double emulsions as templates. Hydrophobic silica nanoparticles that are dispersed in the oil phase stabilize the double emulsions, and subsequently become the shell of the colloidosomes upon removal of the organic solvent as shown in the figure.},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.200800918},
	author = {Lee, Daeyeon and Weitz, David A}
}
@article {154911,
	title = {Drop-based microfluidic devices for encapsulation of single cells},
	journal = {Lab on a Chip},
	volume = {8},
	number = {7},
	year = {2008},
	pages = {1110-1115},
	abstract = {We use microfluidic devices to encapsulate, incubate, and manipulate individual cells in picoliter aqueous drops in a carrier fluid at rates of up to several hundred Hz. We use a modular approach with individual devices for each function, thereby significantly increasing the robustness of our system and making it highly flexible and adaptable to a variety of cell-based assays. The small volumes of the drops enables the concentrations of secreted molecules to rapidly attain detectable levels. We show that single hybridoma cells in 33 pL drops secrete detectable concentrations of antibodies in only 6 h and remain fully viable. These devices hold the promise of developing microfluidic cell cytometers and cell sorters with much greater functionality, allowing assays to be performed on individual cells in their own microenvironment prior to analysis and sorting.},
	url = {https://pubs.rsc.org/en/content/articlelanding/2008/lc/b802941e$\#$!divAbstract},
	author = {Koester, Sarah and Angile, Francesco E. and Duan, Honey and Agresti, Jeremy J. and Wintner, Anton and Schmitz, Christian and Rowat, Amy C. and Merten, Christoph A. and Pisignano, Dario and Griffiths, Andrew D. and Weitz, David A}
}
@article {154851,
	title = {Colloid surfactants for emulsion stabilization},
	journal = {Advanced Materials},
	volume = {20},
	number = {17},
	year = {2008},
	pages = {3239-3243},
	abstract = {Colloid surfactants are fabricated with precisely controlled geometry and used for emulsion stabilization. These amphiphilic dimer particles (left) combine the benefits of emulsion stabilization of particles and the amphiphilicity of molecular surfactants to afford better emulsion stabilization. Remarkably, these colloidal surfactants stabilize not only spherical emulsion droplets but also nonspherical ones (right).},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.200800484},
	author = {Kim, Jin-Woong and Lee, Daeyeon and Shum, Ho Cheung and Weitz, David A}
}
@article {154681,
	title = {Biocompatible surfactants for water-in-fluorocarbon emulsions},
	journal = {Lab on a Chip},
	volume = {8},
	number = {10},
	year = {2008},
	pages = {1632-1639},
	abstract = {Drops of water-in-fluorocarbon emulsions have great potential for compartmentalizing both in vitro and in vivo biological systems; however, surfactants to stabilize such emulsions are scarce. Here we present a novel class of fluorosurfactants that we synthesize by coupling oligomeric perfluorinated polyethers (PFPE) with polyethyleneglycol (PEG). We demonstrate that these block copolymer surfactants stabilize water-in-fluorocarbon oil emulsions during all necessary steps of a drop-based experiment including drop formation, incubation, and reinjection into a second microfluidic device. Furthermore, we show that aqueous drops stabilized with these surfactants can be used for in vitro translation (IVT), as well as encapsulation and incubation of single cells. The compatability of this emulsion system with both biological systems and polydimethylsiloxane (PDMS) microfluidic devices makes these surfactants ideal for a broad range of high-throughput, drop-based applications.},
	url = {https://pubs.rsc.org/en/content/articlelanding/2008/lc/b806706f$\#$!divAbstract},
	author = {C. Holtze and Rowat, A. C. and Agresti, J. J. and Hutchison, J. B. and Angile, F. E. and Schmitz, C. H. J. and Koster, S. and Duan, H. and Humphry, K. J. and Scanga, R. A. and Johnson, J. S. and Pisignano, D. and Weitz, D. A.}
}
@inbook {154486,
	title = {Mechanical response of cytoskeletal networks},
	booktitle = {Biophysical Tools for Biologists, Vol 2: In Vivo Techniques},
	series = {Methods in Cell Biology},
	volume = {89},
	year = {2008},
	pages = {487-519},
	publisher = {Elsevier},
	organization = {Elsevier},
	abstract = {The cellular cytoskeleton is a dynamic network of filamentous proteins, consisting of filamentous actin (F-actin), microtubules, and intermediate filaments. However, these networks are not simple linear, elastic solids; they can exhibit highly nonlinear elasticity and athermal dynamics driven by ATP-dependent processes. To build quantitative mechanical models describing complex cellular behaviors, it is necessary to understand the underlying physical principles that regulate force transmission and dynamics within these networks. In this chapter, we review our current understanding of the physics of networks of cytoskeletal proteins formed in vitro. We introduce rheology, the technique used to measure mechanical response. We discuss our current understanding of the mechanical response of F-actin networks, and how the biophysical properties of F-actin and actin cross-linking proteins can dramatically impact the network mechanical response. We discuss how incorporating dynamic and rigid microtubules into F-actin networks can affect the contours of growing microtubules and composite network rigidity. Finally, we discuss the mechanical behaviors of intermediate filaments.},
	url = {https://www.sciencedirect.com/science/article/pii/S0091679X08006195?via\%3Dihub},
	author = {Gardel, Margaret L. and Kasza, Karen E. and Brangwynne, Clifford P and Liu, Jiayu and Weitz, David A and Correia, J. J. and Detrich, H. W.}
}
@article {154386,
	title = {Controlled encapsulation of single-cells into monodisperse picolitre drops},
	journal = {Lab on a Chip},
	volume = {8},
	number = {8},
	year = {2008},
	pages = {1262-1264},
	abstract = {Encapsulation of cells within picolitre-size monodisperse drops provides new means to perform quantitative biological studies on a single-cell basis for large cell populations. Variability in the number of cells per drop due to stochastic cell loading is a major barrier to these techniques. We overcome this limitation by evenly spacing cells as they travel within a high aspect-ratio microchannel; cells enter the drop generator with the frequency of drop formation.},
	url = {https://pubs.rsc.org/en/content/articlelanding/2008/lc/b805456h$\#$!divAbstract},
	author = {Jon F. Edd and Di Carlo, Dino and Humphry, Katherine J. and Koster, Sarah and Irimia, Daniel and Weitz, David A and Toner, Mehmet}
}
@article {154296,
	title = {Eutectic gallium-indium (EGaIn): A liquid metal alloy for the formation of stable structures in microchannels at room temperature},
	journal = {Advanced Functional Materials},
	volume = {18},
	number = {7},
	year = {2008},
	pages = {1097-1104},
	abstract = {This paper describes the rheological behavior of the liquid metal eutectic gallium-indium (EGaIn) as it is injected into microfluidic channels to form stable microstructures of liquid metal. EGaIn is well-suited for this application because of its theological properties at room temperature: it behaves like an elastic material until it experiences a critical surface stress, at which point it yields and flows readily. These properties allow EGaIn to fill microchannels rapidly when sufficient pressure is applied to the inlet of the channels, yet maintain structural stability within the channels once ambient pressure is restored. Experiments conducted in microfluidic channels, and in a parallel-plate rheometer, suggest that EGaIn{\textquoteright}s behavior is dictated by the properties of its surface (Predominantly gallium oxide, as determined by Auger measurements); these two experiments both yield approximately the same number for the critical surface stress required to induce EGaIn to flow (similar to 0.5 N/m). This analysis-which shows that the pressure that must be exceeded for EGaIn to flow through a microchannel is inversely proportional to the critical (i.e., smallest) dimension of the channel-is useful to guide future fabrication of microfluidic channels to mold EGaIn into functional microstructures.},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.200701216},
	author = {Dickey, Michael D. and Chiechi, Ryan C. and Larsen, RyanJ. and Weiss, Emily A. and Weitz, David A and George M. Whitesides}
}
@article {154201,
	title = {Droplet-based microfluidic platforms for the encapsulation and screening of mammalian cells and multicellular organisms},
	journal = {Chemistry \& Biology},
	volume = {15},
	number = {5},
	year = {2008},
	pages = {427-437},
	abstract = {High-throughput, cell-based assays require small sample volumes to reduce assay costs and to allow for rapid sample manipulation. However, further miniaturization of conventional microtiter plate technology is problematic due to evaporation and capillary action. To overcome these limitations, we describe droplet-based microfluidic platforms in which cells are grown in aqueous microcompartments separated by an inert perfluorocarbon carrier oil. Synthesis of biocompatible surfactants and identification of gas-permeable storage systems allowed human cells, and even a Multicellular organism (C. elegans), to survive and proliferate within the microcompartments for several days. Microcompartments containing single cells could be reinjected into a microfluidic device after incubation to measure expression of a reporter gene. This should open the way for high-throughput, cell-based screening that can use \&gt;1000-fold smaller assay volumes and has similar to 500x higher throughput than conventional microtiter plate assays.},
	url = {https://www.sciencedirect.com/science/article/pii/S1074552108001506?via\%3Dihub},
	author = {Clausell-Tormos, Jenifer and Lieber, Diana and Baret, Jean-Christophe and El-Harrak, Abdeslam and Miller, Oliver J. and Frenz, Lucas and Blouwolff, Joshua and Humphry, Katherine J. and Koster, Sarah and Duan, Honey and Holtze, Christian and Weitz, David A and Griffiths, Andrew D. and Merten, Christoph A.}
}
@article {154151,
	title = {Highly responsive hydrogel scaffolds formed by three-dimensional organization of microgel nanoparticles},
	journal = {Nano Letters},
	volume = {8},
	number = {1},
	year = {2008},
	pages = {168-172},
	abstract = {We present a robust and straightforward method for fabricating remarkably responsive hydrogel scaffolds consisting of submicron-sized microgel particles. We demonstrate that the microgel particles assemble either through bridging or depletion interactions to yield a structure that swells or deswells at a macroscopic level in much shorter times as compared to a bulk polymer gel of similar characteristics. This approach offers a new way of fabricating functional hydrogel scaffolds with controllable responsiveness to applied stimuli and excellent loading capability for a wide variety of materials, irrespective of chemistry, size, and shape.},
	url = {https://pubs.acs.org/doi/abs/10.1021/nl072346e},
	author = {Cho, Eun Chul and Kim, Jin-Woong and Fernandez-Nieves, Alberto and Weitz, David A}
}
@article {154106,
	title = {Droplet-based microfluidics for emulsion and solvent evaporation synthesis of monodisperse mesoporous silica microspheres},
	journal = {Langmuir},
	volume = {24},
	number = {3},
	year = {2008},
	pages = {658-661},
	abstract = {A novel method for the fabrication of monodisperse mesoporous silica particles is suggested. It is based on the formation of well-defined equally sized emulsion droplets using a microfluidic approach. The droplets contain the silica precursor/surfactant solution and are suspended in hexadecane as the continuous oil phase. The solvent is then expelled from the droplets, leading to concentration and micellization of the surfactant. At the same time, the silica solidifies around the surfactant structures, forming equally sized mesoporous particles. The procedure can be tuned to produce well-separated particles or alternatively particles that are linked together. The latter allows us to create 2D or 3D structures with hierarchical porosity.},
	url = {https://pubs.acs.org/doi/10.1021/la7032516},
	author = {Carroll, Nick J. and Rathod, Shailendra B. and Derbins, Erin and Mendez, Sergio and Weitz, David A and Petsev, Dimiter N.}
}
@article {154056,
	title = {Cytoplasmic diffusion: Molecular motors mix it up},
	journal = {Journal of Cell Biology},
	volume = {183},
	number = {4},
	year = {2008},
	pages = {583-587},
	abstract = {Random motion within the cytoplasm gives rise to molecular diffusion; this motion is essential to many biological processes. However, in addition to thermal Brownian motion, the cytoplasm also undergoes constant agitation caused by the activity of molecular motors and other nonequilibrium cellular processes. Here, we discuss recent work that suggests this activity can give rise to cytoplasmic motion that has the appearance of diffusion but is significantly enhanced in its magnitude and which can play an important biological role, particularly in cytoskeletal assembly.},
	url = {https://rupress.org/jcb/article/183/4/583/45669/Cytoplasmic-diffusion-molecular-motors-mix-it-up},
	author = {Brangwynne, Clifford P and Koenderink, Gijsje H and MacKintosh, Frederick C and Weitz, David A}
}
@article {154061,
	title = {Nonequilibrium microtubule fluctuations in a model cytoskeleton},
	journal = {Physical Review Letters},
	volume = {100},
	number = {11},
	year = {2008},
	pages = {118104},
	abstract = {Biological activity gives rise to nonequilibrium fluctuations in the cytoplasm of cells; however, there are few methods to directly measure these fluctuations. Using a reconstituted actin cytoskeleton, we show that the bending dynamics of embedded microtubules can be used to probe local stress fluctuations. We add myosin motors that drive the network out of equilibrium, resulting in an increased amplitude and modified time dependence of microtubule bending fluctuations. We show that this behavior results from steplike forces on the order of 10 pN driven by collective motor dynamics.},
	url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.100.118104},
	author = {Brangwynne, Clifford P and Koenderink, Gijsje H and MacKintosh, Frederick C and Weitz, David A}
}
@article {154026,
	title = {A quantitative analysis of contractility in active cytoskeletal protein networks},
	journal = {Biophysical Journal},
	volume = {94},
	number = {8},
	year = {2008},
	pages = {3126-3136},
	abstract = {Cells actively produce contractile forces for a variety of processes including cytokinesis and motility. Contractility is known to rely on myosin II motors which convert chemical energy from ATP hydrolysis into forces on actin filaments. However, the basic physical principles of cell contractility remain poorly understood. We reconstitute contractility in a simplified model system of purified F-actin, muscle myosin II motors, and a-actinin cross-linkers. We show that contractility occurs above a threshold motor concentration and within a window of cross-linker concentrations. We also quantify the pore size of the bundled networks and find contractility to occur at a critical distance between the bundles. We propose a simple mechanism of contraction based on myosin filaments pulling neighboring bundles together into an aggregated structure. Observations of this reconstituted system in both bulk and low-dimensional geometries show that the contracting gels pull on and deform their surface with a contractile force of similar to 1 mu N, or similar to 100 pN per F-actin bundle. Cytoplasmic extracts contracting in identical environments show a similar behavior and dependence on myosin as the reconstituted system. Our results suggest that cellular contractility can be sensitively regulated by tuning the (local) activity of molecular motors and the cross-linker density and binding affinity.},
	url = {https://www.cell.com/biophysj/fulltext/S0006-3495(08)70469-7},
	author = {Bendix, Paul M. and Koenderink, Glisje H. and Cuvelier, Damien and Dogic, Zvonimir and Koeleman, Bernard N and Brieher, William M and Field, Christine M and Mahadevan, L and Weitz, David A}
}
@article {153886,
	title = {Single-layer membrane valves for elastomeric microfluidic devices},
	journal = {Applied Physics Letters},
	volume = {92},
	number = {24},
	year = {2008},
	pages = {243509},
	abstract = {We characterize single-layer membrane valves for elastomeric microfluidic devices. The devices are simple to fabricate using standard single-layer softlithography; moreover, they afford continuous control over flow rate. This combines the simplicity of stamped microfluidic devices with the precision control of membrane valves, which we demonstrate by steering objects in the flow using a simple device. (c) 2008 American Institute of Physics.},
	url = {https://aip.scitation.org/doi/10.1063/1.2945797},
	author = {A. R. Abate and Weitz, D. A.}
}
@article {153851,
	title = {Glass coating for PDMS microfluidic channels by sol-gel methods},
	journal = {Lab on a Chip},
	volume = {8},
	number = {4},
	year = {2008},
	pages = {516-518},
	abstract = {Soft lithography using polydimethylsiloxane (PDMS) allows one to fabricate complex microfluidic devices easily and at low cost. However, PDMS swells in the presence of many organic solvents significantly degrading the performance of the device. We present a method to coat PDMS channels with a glass-like layer using sol-gel chemistry. This coating greatly increases chemical resistance of the channels; moreover, it can be functionalized with a wide range of chemicals to precisely control interfacial properties. This method combines the ease of fabrication afforded by soft-lithography with the precision control and chemical robustness afforded by glass.},
	url = {https://pubs.rsc.org/en/content/articlelanding/2008/lc/b800001h$\#$!divAbstract},
	author = {Abate, Adam R. and Lee, Daeyeon and Do, Thao and Holtze, Christian and Weitz, David A}
}
@article {153841,
	title = {Photoreactive coating for high-contrast spatial patterning of microfluidic device wettability},
	journal = {Lab on a Chip},
	volume = {8},
	number = {12},
	year = {2008},
	pages = {2157-2160},
	abstract = {For many applications in microfluidics, the wettability of the devices must be spatially controlled. We introduce a photoreactive sol-gel coating that enables high-contrast spatial patterning of microfluidic device wettability.},
	url = {https://pubs.rsc.org/en/content/articlelanding/2008/lc/b813405g$\#$!divAbstract},
	author = {Abate, Adam R. and Krummel, Amber T. and Lee, Daeyeon and Marquez, Manuel and Holtze, Christian and Weitz, David A}
}
