Batteries based on three dimensional microstructures are expected to offer significant advantages in comparison to conventional two dimensional batteries. One of the key elements for creating new types of 3D microbatteries is fabricating high-aspect-ratio carbon structures. Our efforts on building positive photoresist structures include: (1) casting photoresist in 3D molds made by DRIE before pyrolysis; (2) multi-exposure and multi-developing processes, and (3) using embedded masks in multi-layer photoresists. Another effort is the fabrication of high-aspect-ratio carbon structures using negative photoresist. We manufactured high-aspect-ratio (~10:1) carbon posts by pyrolysis from negative photoresists in a simple one-step process. Simulation results showed that current density is strongly influenced by the biasing pattern and the geometry of the electrodes themselves. Current density (and therefore power density) is stronger at the edge of electrodes-implying that closer spacing of the electrodes will provide a denser current concentration. Electrochemical tests demonstrate that these C-MEMS electrodes can be charged/discharged with Li. A C-MEMS battery approach has the potential to solve both manufacturing and materials problems simultaneously.
A DNA hybridization and detection unit was developed for a compact disc (CD) platform. The compact disc was used as the fluidic platform for sample and reagent manipulation using centrifugal force. Chambers for reagent storage and conduits for fluidic functions were replicated from polydimethylsiloxane (PDMS) using an SU-8 master mold fabricated with a 2-level lithography process we developed specially for the microfluidic structures used in this work. For capture probes, we used self-assembled DNA oligonucleotide monolayers (SAMs) on gold pads patterned on glass slides. The PDMS flow cells were aligned with and sealed against glass slides to form the DNA hybridization detection units. Both an enzymatic-labeled fluorescence technique and a bioluminescent approach were used for hybridization detection. An analytical model was introduced to quantitatively predict the accumulation of hybridized targets. The flow-through hybridization units were tested using DNA samples (25-mers) of different concentrations down to 1 pM and passive assays (no flow), using samples of the same concentrations, were performed as controls. At low concentrations, with the same hybridization time, a significantly higher relative fluorescence intensity was observed in both enzymatic and bioluminescent flow-through assays compared to the corresponding passive hybridization assays. Besides the fast hybridization rate, the CD-based method has the potential for enabling highly automated, multiple and self-contained assays for DNA detection.