David A. Weitz

The biophysical properties of lipid vesicles are important for their stability and integrity; they are also important for controlling the performance when these vesicles are used for drug delivery. The vesicle properties are determined by the composition of lipids used to form the vesicle. However, for a given lipid composition, they can also be tailored by tethering of polymers to the membrane. Typically, synthetic polymers like polyethylene glycol are used to increase vesicle stability but polysaccharides are much less explored. Here, we report a general method to functionalize lipid vesicles with polysaccharides by binding them to cholesterol. We incorporate the polysaccharides on the outer membrane leaflet of giant unilamellar vesicles (GUVs) and investigate their effect on membrane mechanics using micropipette aspiration. We find that the presence of the glycolipid produces an unexpected softening of GUVs with fluid …

Over the past two decades, advances in droplet-based microfluidics have facilitated new approaches to process and analyze samples with unprecedented levels of precision and throughput. A wide variety of applications has been inspired across multiple disciplines ranging from materials science to biology. Understanding the dynamics of droplets enables optimization of microfluidic operations and design of new techniques tailored to emerging demands. In this review, we discuss the underlying physics behind high-throughput generation and manipulation of droplets. We also summarize the applications in droplet-derived materials and droplet-based lab-on-a-chip biotechnology. In addition, we offer perspectives on future directions to realize wider use of droplet microfluidics in industrial production and biomedical analyses.

Fractures are ubiquitous and can lead to the catastrophic material failure of materials. Although fracturing in a two-dimensional plane is well understood, all fractures are extended in and propagate through three-dimensional space. Moreover, their behaviour is complex. Here we show that the forward propagation of a fracture front occurs through an initial rupture, nucleated at some localized position, followed by a very rapid transverse expansion at velocities as high as the Rayleigh-wave speed. We study fracturing in a circular geometry that achieves an uninterrupted extended fracture front and use a fluid to control the loading conditions that determine the amplitude of the forward jump. We find that this amplitude correlates with the transverse velocity. Dynamic rupture simulations capture the observations for only a high transverse velocity. These results highlight the importance of transverse dynamics in the …

Methods for analyzing DNA-containing samples are provided. The methods can comprise isolating a single genomic equivalent of DNA from the DNA-containing sample to provide a single isolated DNA molecule. The single isolated DNA molecule can be subjected to amplification conditions in the presence of one or more sets of unique molecularly tagged primers to provide one or more amplicons. Any spurious allelic sequences generated during the amplification process are tagged with an identical molecular tag. The methods can also include a step of determining the sequence of the one or more amplicons, in which the majority sequence for each code is selected as the sequence of the single original encapsulated target. The DNA-containing sample can be a forensic sample (eg, mixed contributor sample), a fetal genetic screening sample, or a biological cell.

2018-06-28 Assigned to PRESIDENT AND FELLOWS OF HARVARD COLLEGE reassignment PRESIDENT AND FELLOWS OF HARVARD COLLEGE ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: Weitz, David A.

High-throughput screening is an indispensable technology in drug discovery, cancer therapy, and disease diagnosis, and it could greatly reduce time cost, reagent consumption, and labor expense. Here, four high-throughput screening methods with high sensitivity and accessibility are discussed in detail. Fluorescence, DNA, heavy metal, and nonmetal isotope barcodes, which generally label antibodies, proteins, and saccharides to identify cells, are detected by flow cytometry, second-generation DNA sequencing, mass cytometry, and second-ion mass spectrometry, respectively. Encoding binary information in barcodes, labeling individual cells by barcodes, performing the characterization of cells together, and identifying the result belonging to individual cells via barcodes are the main steps for high-throughput screening. Applications of the four digital barcodes in high-throughput screening for both in vitro and in …

The pursuit of materials with enhanced functionality has led to the emergence of metamaterials—artificially engineered materials whose properties are determined by their structure rather than composition. Traditionally, the building blocks of metamaterials are arranged in fixed positions within a lattice structure, , , , , , , , , , , , , , , , , –. However, recent research has revealed the potential of mixing disconnected building blocks in a fluidic medium, , , , , , –. Inspired by these recent advances, here we show that by mixing highly deformable spherical capsules into an incompressible fluid, we can realize a ‘metafluid’ with programmable compressibility, optical behaviour and viscosity. First, we experimentally and numerically demonstrate that the buckling of the shells endows the fluid with a highly nonlinear behaviour. Subsequently, we harness this behaviour to develop smart robotic systems, highly tunable logic gates and …

X01. 00005: A Taste of Chocolate: Have your non-equilibrium physics and eat it too!