Ehrmann Klaus, Saillen Nicolas, Vincent Franck, Stettler Matthieu, Jordan Martin, Wurm Florian Maria, Besse Pierre-André, Popovic Radivoje
Microsystems Laboratory, EPFL-Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland.
Lab Chip. 2007 Mar;7(3):373-80. doi: 10.1039/b614044k. Epub 2007 Jan 11.
NMR-microprobes based on solenoids and Helmholtz coils have been microfabricated and NMR-spectra of mammalian cells have successfully been taken. The microfabrication technology developed for these probes consists of three electroplated copper levels for low resistance coils and three SU-8 layers for the integration of microchannels. This technology allows fabricating solenoids, Helmholtz and planar coils on the same wafer. The coils have inner diameters in the range of 160 to 400 microm and detection volumes of 5 to 22 nL. The solenoid and Helmholtz coils show improved RF-field characteristics compared to a planar coil fabricated with the same process. The fabricated solenoid has a particularly low resistance of only 0.46 Omega at 300 MHz. Moreover, it is very sensitive and has a very uniform RF-field, but shows large line width. The Helmholtz coils are slightly less sensitive, but display a far narrower line width, and are therefore a good compromise. With a Helmholtz coil, a SNR of 620 has been measured after one scan on 9 nL pure water. An NMR-microprobe based on a Helmholtz coil has also been used to take spectra of CHO cells that have been concentrated in the sensitive region of the coil with a mechanical filter integrated into the channel.
基于螺线管和亥姆霍兹线圈的核磁共振微探头已被微制造出来，并成功获取了哺乳动物细胞的核磁共振谱。为这些探头开发的微制造技术包括用于低电阻线圈的三层电镀铜层和用于微通道集成的三层SU-8层。该技术允许在同一晶圆上制造螺线管、亥姆霍兹线圈和平面线圈。这些线圈的内径在160至400微米范围内，检测体积为5至22纳升。与采用相同工艺制造的平面线圈相比，螺线管和亥姆霍兹线圈具有更好的射频场特性。所制造的螺线管在300兆赫时电阻特别低，仅为0.46欧姆。此外，它非常灵敏，射频场非常均匀，但线宽较大。亥姆霍兹线圈的灵敏度略低，但线宽要窄得多，因此是一个很好的折衷方案。使用亥姆霍兹线圈，在对9纳升纯水进行一次扫描后，测得的信噪比为620。基于亥姆霍兹线圈的核磁共振微探头也已用于获取CHO细胞的谱图，这些细胞已通过集成在通道中的机械过滤器集中在线圈的敏感区域。
