Stanford University Home

Research Highlights

DNA-tethered Membrane Formation From Giant Unilamellar Vesicles

boxer.jpg We have developed two strategies for preparing tethered lipid bilayer membrane patches on solid surfaces by DNA hybridization. In the first strategy, single-stranded DNA strands are immobilized by click chemistry to a silica surface, whose remaining surface is passivated to prevent direct assembly of a solid supported bilayer. Then giant unilamellar vesicles (GUVs) displaying the anti-sense strand based on a DNA-lipid conjugate are allowed to tether, spread, and rupture to form tethered bilayer patches. In the second strategy, a supported lipid bilayer displaying the DNA-lipid conjugate is first assembled on the surface. Then GUVs displaying the anti-sense strand are allowed to tether, spread and rupture to form tethered bilayer patches.

Green Chemistry of Poly(l-lactides)

As part of a series of studies on the green chemistry of poly(l-lactides), we have performed a theoretical study of the mechanism of ring-opening polymerization. We have investigated two alternative mechanisms for the ring-opening polymerization of l-lactide using a guanidine-based catalyst, the first involving acetyl transfer to the catalyst, and the second involving only hydrogen bonding to the catalyst. Using computational chemistry methods, we show that the hydrogen bonding pathway shown above is preferred over the acetyl transfer pathway and that this is consistent with experimental information.

Polymer Dynamics in Concentrated Solution

Polymer Dynamics in Concentrated Solution The dynamics of entangled polymer solutions far from equilibrium is, at present, a subject of considerable interest because the “natural” modifications to tube or reptation-based theories have not been successful. In such systems, polymer molecules are highly entangled, which results in the motion of any given polymer being highly restricted due to interactions with its neighbors. As expected, the dynamics of such a complex fluid is far different from those of the same.

Flow-Enhanced Vesicle Deformation in the Four-roll Mill

Susan Muller, Dept. Chemical Engineering, UC Berkeley
 
This project leverages ongoing research on the dynamics of DNA and vescicles within CPIMA.  We have developed a novel microfluidic four-roll mill that allows all flow types (from extension to shear to rotation) to be accessed and have previously used it to examine DNA tumbling in mixed flows and, […]

Patterning Organic Semiconductor Single Crystal Field-Effect Transistors

Single-crystal organic field-effect transistors (OFETs) are ideal device structures for studying fundamental science associated with charge transport in organic materials and have demonstrated outstanding electrical characteristics. However, it remains a technical challenge to integrate single-crystal devices into practical electronic applications. A key difficulty is that organic single-crystal devices are usually fabricated one device at a time through manual selection and placing individual crystals. To overcome this difficulty, Bao et al. successfully developed two high-throughput approaches to pattern organic single crystal arrays.

Flow-Enhanced Single Molecule DNA Hybridization Studies

Objective: To develop novel microfluidic flow cells that allow trapping of single DNA molecules and studies of the binding of sequence-specific probes to the trapped DNA.

Fig. 2
Approach: Two different devices have been designed and fabricated: a cross-slot that uses flow focusing to direct probes to the trapped DNA and a microfluidic “four roll mill” that allows the flow type to be varied from extension to shear to rotation near the trapped DNA (fig. 2).

Closing the Loop on Recycling: Can We Stop the oil-to-Landfill Treadmill?

Waste PET Processing Poly(ethylene terephthalate) (PET), a widely used engineering thermoplastic for carpet, clothing (fibers), tire cords, soda bottles and other containers, film, automotive, electronics, displays etc., will contribute several billion pounds of waste to landfills this year alone! According to the American Plastics Council, PET packaging was originally used for soft drinks, but packing applications today include other beverages such as water, juice, beer, in addition to other foods such as peanut butter and ketchup and a variety of other household products.

Microfluidic Device for DNA Dynamics in Mixed Flows

DNA tumbling in mixed flows that vary from shear to rotation.Lab-on-a-chip devices that are capable of performing microanalytical testing must have the capacity to precisely control the flow of very small volumes of fluid. The typical approach to this involves microfluidic devices in which the flow channels are of the order of 50 to 100 microns in diameter. Of particular interest in CPIMA has been the use of microfluidic devices that could be used to create flow conditions for capturing and orienting biomolecules that are sufficiently long that they may be visualized with optical microscopy. The prime model system for such experiments has been double-stranded DNA, which could achieve lengths of the order of tens of microns. In recent work, Muller and Shaqfeh have developed microfluidic devices and sequence-specific probes for studies of DNA hybridization kinetics that may also allow DNA genotyping with unprecedented read lengths.

Verticle Nanopore Bulk Heterojunction Solar Cells

A major effort in CPIMA has been to control and characterize interfacial charge transport in directed nanoassemblies. Such research is motivated by basic issues that relate to the performance of organic electronic devices, including photovoltaics, field-effect transistors, biological sensors, and memory elements. This highlight focuses on recent activity in photovoltaics. Prior work in CPIMA by McGehee in collaboration with Miller has demonstrated that poly(3-hexylthiophene) (P3HT) has much larger charge carrier mobility when confined in straight nanopores than when confined in disordered nanopores.

Patterning of Large Arrays of Organic Semiconductor Single Crystals

Field-effect transistors made of single organic crystals are ideal for studying the charge transport characteristics of organic semiconductor materials. Their outstanding device performance, relative to that of transistors made of organic thin films, makes them also attractive candidates for electronic applications such as active matrix displays and sensor arrays. The only approach currently available […]