Zhang, L. ; Chen, K. ; Zhang, H. ; Pang, B. ; Choi, C. - H. ; Mao, A. S. ; Liao, H. ; Utech, S. ; Mooney, D. J. ; Wang, H. ; et al. Microfluidic Templated Multicompartment Microgels for 3D Encapsulation and Pairing of Single Cells. Small 2018, 14, 1-8. Publisher's VersionAbstract
Controlled encapsulation and pairing of single cells within a confined 3D matrix can enable the replication of the highly ordered cellular structure of human tissues. Microgels with independently controlled compartments that can encapsulate cells within separately confined hydrogel matrices would provide precise control over the route of pairing single cells. Here, a one‐step microfluidic method is presented to generate monodisperse multicompartment microgels that can be used as a 3D matrix to pair single cells in a highly biocompatible manner. A method is presented to induce microgels formation on chip, followed by direct extraction of the microgels from oil phase, thereby avoiding prolonged exposure of the microgels to the oil. It is further demonstrated that by entrapping stem cells with niche cells within separate but adjacent compartments of the microgels, it can create complex stem cell niche microenvironments in a controlled manner, which can serve as a useful tool for the study of cell–cell interactions. This microfluidic technique represents a significant step toward high‐throughput single cells encapsulation and pairing for the study of intercellular communications at single cell level, which is of significant importance for cell biology, stem cell therapy, and tissue engineering.
Atia, L. ; Bi, D. ; Sharma, Y. ; Mitchel, J. A. ; Gweon, B. ; Koehler, S. A. ; DeCamp, S. J. ; Lan, B. ; Kim, J. H. ; Hirsch, R. ; et al. Geometric constraints during epithelial jamming. Nature Physics 2018. Publisher's VersionAbstract
As an injury heals, an embryo develops or a carcinoma spreads, epithelial cells systematically change their shape. In each of these processes cell shape is studied extensively whereas variability of shape from cell to cell is regarded most often as biological noise. But where do cell shape and its variability come from? Here we report that cell shape and shape variability are mutually constrained through a relationship that is purely geometrical. That relationship is shown to govern processes as diverse as maturation of the pseudostratified bronchial epithelial layer cultured from non-asthmatic or asthmatic donors, and formation of the ventral furrow in the Drosophila embryo. Across these and other epithelial systems, shape variability collapses to a family of distributions that is common to all. That distribution, in turn, is accounted for by a mechanistic theory of cell–cell interaction, showing that cell shape becomes progressively less elongated and less variable as the layer becomes progressively more jammed. These findings suggest a connection between jamming and geometry that spans living organisms and inert jammed systems, and thus transcends system details. Although molecular events are needed for any complete theory of cell shape and cell packing, observations point to the hypothesis that jamming behaviour at larger scales of organization sets overriding geometric constraints.
Edery, Y. ; Berg, S. ; Weitz, D. Surfactant Variations in Porous Media Localize Capillary Instabilities during Haines Jumps. Physical Review Letters 2018, 120. Publisher's VersionAbstract
We use confocal microscopy to measure velocity and interfacial tension between a trapped wetting phase with a surfactant and a flowing, invading nonwetting phase in a porous medium. We relate interfacial tension variations at the fluid-fluid interface to surfactant concentration and show that these variations localize the destabilization of capillary forces and lead to rapid local invasion of the nonwetting fluid, resulting in a Haines jump. These spatial variations in surfactant concentration are caused by velocity variations at the fluid-fluid interfaces and lead to localization of the Haines jumps even in otherwise very uniform pore structure and pressure conditions. Our results provide new insight into the nature of Haines jumps, one of the most ubiquitous and important instabilities in flow in porous media.
Zhang, H. ; Zhu, Y. ; Qu, L. ; Wu, H. ; Kong, H. ; Yang, Z. ; Chen, D. ; Mäkilä, E. ; Salonen, J. ; Santos, H. A. ; et al. Gold nanorods conjugated porous silicon nanoparticles encapsulated in calcium alginate nano hydrogels using microemulsion templates. Nano Letters 2018, 18, 1448-1453. Publisher's Version hongbo_zhang_et_al_2018_nanoletters.pdf
Montessori, A. ; Lauricella, M. ; La Rocca, M. ; Succi, S. ; Stolovicki, E. ; Zibalt, R. ; Weitz, D. Regularized lattice Boltzmann multicomponent models for low capillary and Reynolds microfluidics flows. Computers & Fluids 2018, 167, 33-39. Publisher's VersionAbstract
We present a regularized version of the color gradient lattice Boltzmann (LB) scheme for the simulation of droplet formation in microfluidic devices of experimental relevance. The regularized version is shown to provide computationally efficient access to capillary number regimes relevant to droplet generation via microfluidic devices, such as flow-focusers and the more recent microfluidic step emulsifier devices.
Stolovicki, E. ; Ziblat, R. ; Weitz, D. A. Throughput enhancement of parallel step emulsifier devices by shear-free and efficient nozzle clearance. Lab on a Chip 2018, 132-138. Publisher's Version
Alim, K. ; Parsa, S. ; Weitz, D. A. ; Brenner, M. P. Local Pore Size Correlations Determine Flow Distributions in Porous Media. Physical Review Letters 2017, 119, 144501. Publisher's Version
Zhang, H. ; Qu, X. ; Chen, H. ; Kong, H. ; Ding, R. ; Chen, D. ; Zhang, X. ; Pei, H. ; Santos, H. A. ; Hai, M. ; et al. Fabrication of Calcium Phosphate-Based Nanocomposites Incorporating DNA Origami, Gold Nanorods, and Anticancer drugs for Biomedical Applications. Advanced Healthcare Materials 2017, 6. Publisher's Version
Wu, J. ; Cai, L. - H. ; Weitz, D. A. Tough Self-Healing Elastomers by Molecular Enforced Integration of Covalent and Reversible Networks. Advanced Materials 2017, 29, 1702616. Publisher's Version 2017_advmater_wucai.pdf
Pegoraro, A. F. ; Janmey, P. ; Weitz, D. A. Mechanical Properties of the Cytoskeleton and Cells. Cold Spring Harbor-Perspectives in Biology 2017, 1-12. Publisher's VersionAbstract

The cytoskeleton is the major mechanical structure of the cell; it is a complex, dynamic
biopolymer network comprising microtubules, actin, and intermediate filaments. Both the
individual filaments and the entire network are not simple elastic solids but are instead highly nonlinear structures. Appreciating the mechanics of biopolymer networks is key to under-
standing the mechanics of cells. Here, we review the mechanical properties of cytoskeletal polymers and discuss the implications for the behavior of cells.

Ung, W. L. ; Mutafopulos, K. ; Spink, P. ; Rambach, R. W. ; Franke, T. ; Weitz, D. A. Enhanced Surface Acoustic Wave Cell Sorting by 3D Microfluidic-Chip Design. Lab on a Chip 2017, 17, 4059-4069. Publisher's VersionAbstract
We demonstrate an acoustic wave driven microfluidic cell sorter that combines advantages of multilayer device fabrication with planar surface acoustic wave excitation. We harness the strong vertical component of the refracted acoustic wave to enhance cell actuation by using an asymmetric flow field to increase cell deflection. Precise control of the 3-dimensional flow is realized by topographical structures implemented on the top of the microchannel. We experimentally quantify the effect of the structure dimensions and acoustic parameter. The design attains cell sorting rates and purities approaching those of state of the art fluorescence-activated cell sorters with all the advantages of microfluidic cell sorting.
Chaudhuri, M. ; Allahyarov, E. ; Löwen, H. ; Egelhaaf, S. U. ; Weitz, D. A. Triple Junction at the Triple Point Resolved on the Individual Particle Level. Phys. Rev. Lett. 2017, 119, 128001. 2017_prl_chaudhrui.pdf
Zhao, C. - X. ; Chen, D. ; Hui, Y. ; Weitz, D. A. ; Middelberg, A. P. J. Controlled Generation of Ultrathin-Shell Double Emulsions and Studies on Their Stability. ChemPhysChem 2017, 18, 1393–1399. 2017_chemphyschem_zhao_1.pdf
Beroz, F. ; Jawerth, L. M. ; Münster, S. ; Weitz, D. A. ; Broedersz, C. P. ; Wingreen, N. S. Physical limits to biomechanical sensing in disordered fibre networks. Nature communications 2017, 8 16096. 2017_natcomm_beroz.pdf
Kong, L. ; Amstad, E. ; Hai, M. ; Ke, X. ; Chen, D. ; Zhao, C. - X. ; Weitz, D. A. Biocompatible microcapsules with a water core templated from single emulsions. Chinese Chemical Letters 2017.
Fan, J. ; Kim, S. - H. ; Chen, Z. ; Zhou, S. ; Amstad, E. ; Lin, T. ; Weitz, D. A. Creation of Faceted Polyhedral Microgels from Compressed Emulsions. Small 2017. 2017_small_fan.pdf
Zhang, W. ; Abbaspourrad, A. ; Chen, D. ; Campbell, E. ; Zhao, H. ; Li, Y. ; Li, Q. ; Weitz, D. A. Osmotic Pressure Triggered Rapid Release of Encapsulated Enzymes with Enhanced Activity. Advanced Functional Materials 2017. 2017_afm_zhang.pdf
Amstad, E. ; Chen, X. ; Eggersdorfer, M. ; Cohen, N. ; Kodger, T. E. ; Ren, C. L. ; Weitz, D. A. Parallelization of microfluidic flow-focusing devices. Physical Review E 2017, 95, 043105. 2017_pre_amstad.pdf
Kodger, T. E. ; Lu, P. J. ; Wiseman, G. R. ; Weitz, D. A. Stable, fluorescent PMMA particles for long-term observation of slow colloidal dynamics. Langmuir 2017. 2017_langmuir_kodger.pdf
Atia, L. ; Bi, D. ; Sharma, Y. ; Mitchel, J. A. ; Gweon, B. ; Koehler, S. ; DeCamp, S. J. ; Lan, B. ; Hirsch, R. ; Pegoraro, A. F. ; et al. Universal geometric constraints during epithelial jamming. arXiv preprint arXiv:1705.04660 2017. 2017_arxiv_atia.pdf