Electronic characterization of lithographically patterned microcoils for high sensitivity NMR detection.
Nuclear magnetic resonance (NMR) offers a non-destructive, powerful, structure-specific analytical method for the identification of chemical and biological systems. The use of radio frequency (RF) microcoils has been shown to increase the sensitivity in mass-limited samples. Recent advances in micro-receiver technology have further demonstrated a substantial increase in mass sensitivity [D.L. Olson, T.L. Peck, A.G. Webb, R.L. Magin, J.V. Sweedler, High-resolution microcoil H-1-NMR for mass-limited, nanoliter-volume samples, Science 270 (5244) (1995) 1967-1970]. Lithographic methods for producing solenoid microcoils possess a level of flexibility and reproducibility that exceeds previous production methods, such as hand winding microcoils. This paper presents electrical characterizations of RF microcoils produced by a unique laser lithography system that can pattern three dimensional surfaces and compares calculated and experimental results to those for wire wound RF microcoils. We show that existing optimization conditions for RF coil design still hold true for RF microcoils produced by lithography. Current lithographic microcoils show somewhat inferior performance to wire wound RF microcoils due to limitations in the existing electroplating technique. In principle, however, when the pitch of the RF microcoil is less than 100mum lithographic coils should show comparable performance to wire wound coils. In the cases of larger pitch, wire cross sections can be significantly larger and resistances lower than microfabricated conductors.
Demas
Vasiliki
V
Science and Technology Principle Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA.
Bernhardt
Anthony
A
Malba
Vince
V
Adams
Kristl L
KL
Evans
Lee
L
Harvey
Christopher
C
Maxwell
Robert S
RS
Herberg
Julie L
JL
D000465:Algorithms; D003198:Computer Simulation; D003300:Copper; D004574:Electromagnetic Fields; D004867:Equipment Design; D007834:Lasers; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D015233:Models, Statistical; D036103:Nanotechnology
D003300:Copper