FY2010 - Oak Ridge National Laboratory

Director’s R&D Fund—
Science for Extreme Environment: Advanced Materials and Interfacial Processes for Energy
detection technology resulting from this research, may be exploited for cross-cutting programs such as
national security.
Results and Accomplishments
The first deliverable was design and fabrication of nanochannel crossbar devices. We have successfully
fabricated channel crossbar devices in polydimethylsiloxane (PDMS), with channel widths below 1 m,
using combinations of electron beam and optical lithography. For the second deliverable, control of
droplet formation and injection into the oil phase, we have developed a method for creating discrete
femtoliter-scale (10 -15 L) water-in-oil droplets, based solely on a geometrically induced reduction in
oil/water interfacial area at microfabricated junction orifices. Monodisperse droplets could be created at
regular intervals under constant pressure conditions, allowing each droplet to be tracked and manipulated
individually in real time, or pressure pulses could be applied to generate one, two, or more droplets per
pulse reproducibly, without the need for additional actuation or detection equipment beyond a pressure
regulator. For the third deliverable, control of fusion of aqueous droplets in the oil phase, we included a
second droplet-generating channel to facilitate on-demand droplet generation and fusion of two or more
droplets. With this system, fusion and chemical reaction initiation times on the order of 1 millisecond or
less were demonstrated, as well as a reversible chemical toggle switch based on alternating fusion of
droplets containing acidic or basic solution, monitored with pH-dependent fluorescence in the product
droplet. For the fourth deliverable, we are adapting methods we have previously used successfully for
passivating the PDMS channel walls (Jung et al. 2008, Langmuir 24, 4439) to prevent nonspecific
adsorption of enzymes in the aqueous channel before capture in water-in-oil droplets.
Information Shared
Jung, S.-Y., Retterer, S. T., and C. P. Collier. 2010. “On-Demand Generation of Monodisperse Femtolitre
Droplets by Shape-Induced Shear.” Lab on a Chip 10, 2688–2694.
Jung, S.-Y., Retterer, S. T., and C. P. Collier. In press. “Interfacial Tension Controlled Fusion of
Individual Femtolitre Droplets and Triggering of Confined Chemical Reactions on Demand,” Lab on
a Chip.
05388
Multiphase Self-Organized Interfaces for Polymer Photovoltaic
Technologies
S. M. Kilbey II, Bobby B. Sumpter, Deanna L. Pickel, William T. Heller, Miguel Fuentes-Cabrera,
John Ankner, Robert Shaw, Jihua Chen, Jose Alonzo Calderon, and Mark Dadmun
Project Description
Through a joint experimental and theoretical/computational effort, we tackle the underlying science
needed to develop nanoparticle-polymer photovoltaic (PV) devices having tailored heterojunction
interfaces comprising self-organized blends of semiconducting conjugated polymers and semiconductor
quantum dots, as well as conjugated polymer/fullerene composites. Understanding how to optimize
heterojunction interfaces and to promote long-range order in bulk heterojunction thin films is crucial for
the development of low-cost, efficient polymer-based PV cells. Research activities aimed at
understanding the nanoscale structure and properties of polymer-nanoparticle interfaces will yield
fundamental knowledge of the links between electronic and morphological states of the systems,
ultimately enabling the ability to tailor blends comprising semiconducting quantum dots or fullerenes
24