Microscale Singlet Oxygen Generator for MEMS-based COIL Lasers
Conventional chemical oxygen iodine lasers (COIL) offer several important advantages for materials processing, including short wavelength (1.3 micrometers) and high power. However, COIL lasers typically employ large hardware and use reactants relatively inefficiently. This project is creating an alternative approach called microCOIL. In microCOIL, most conventional components are replaced by a set of silicon MEMS devices that offer smaller hardware and improved performance. A complete microCOIL system includes microchemical reactors, microscale supersonic nozzles, and micropumps. System models incorporating all of these elements predict significant performance advantages in the microCOIL approach [1].
Initial work is focused on the design, microfabrication, and demonstration of a chip-scale singlet oxygen generator (SOG), a microchemical reactor that generates singlet delta oxygen gas to power the laser. Given the extensive experience with micro-chemical reactors over the last decade [2], it is not surprising that a microSOG would offer a significant performance gain over large-scale systems. The gain stems from basic physical scaling; surface to volume ratio increases as the size scale is reduced, which enables improved mixing and heat tranfer. The SOG chip being demonstrated in this project employs an array of microstructure packed-bed reaction channels interspersed with microscale cooling channels for efficient heat removal [3]. To date the device has produced oxygen concentrations of 1017 cm-3, yields approaching 80%, and molar flowrates in excess of 600 moles/L/sec [4]. The yield and molar flowrates compare favorably with macroscale SOG designs.
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| Figure 1: A - View of a chip surface showing flow resulting from singlet-oxygen production; B - View of packaging and optics surrounding microSOC; C - Photograph of microSOG. | Figure 2: IR spectra measured at the microSOG gas outlet versus time. The peak at 1268nm indicates the spontaneous decay of singlet oxygen into its triplet state. |
Current Team Members: Tyrone Hill, Luis Fernando Velasquez-Garcia, A. Epstein, K. F. Jensen, and C. Livermore
Current Sponsorship: DARPA, MDA, AFRL.
References:
[1] B.A. Wilhite, C. Livermore, Y. Gong, A.H. Epstein, and K.F. Jensen, "Design of a MEMS-based microChemical oxygen-iodine laser (mCOIL) system", IEEE Journal of Quantum Electronics, 40, 1041-1055 (2004).
[2] M.W. Losey, M.A. Schmidt, K.F. Jensen, "Microfabricated Multiphase Packed-Bed Reactors: Characterization of Mass Transfer and Reactions," Ind. Eng. Chem. Res., 40, 2555-2562 (2001).
[3] L.F. Velasquez-Garcia, T.F. Hill, B.A. Wilhite, K.F. Jensen, A.H. Epstein, and C. Livermore, "A MEMS Singlet Oxygen Generator - Part I: Device Fabrication and Proof of Concept Demonstration," to appear in IEEE J. of Microelectromechanical Systems, 2007.
[4] T.F. Hill, L.F. Velasquez-Garcia, B.A. Wilhite, W.T. Rawlins, S. Lee, S.J. Davis, K.F. Jensen, A.H. Epstein, and C. Livermore, "A MEMS Singlet Oxygen Generator - Part II: Experimental Exploration of the Performance Space," submitted to IEEE J. of Microelectromechanical Systems, 2007.