Biomedical Engineering Reference
1-chip NMR system with lab-on-a-chip capability (From Ref. [ 3 ])
operation. For example, a biological sample can be placed directly on the coil of the
chip for on-chip screening of disease markers. The chip can be disposable for one-
time diagnostic testing. The direct interface may also enable oil detection [ 4 ]and
quantum computing [ 5 ] on a silicon chip. The 1-chip system has the same spin-mass
sensitivity as the 2-kg portable system while 60 times more spin-mass sensitive than
the commercial system of [ 1 ].
The key to these two new developments is the new RF transceiver, an advance
from the transceiver in the 2-kg portable system. First, the new transceiver achieves
the sensitivity to cope with the signal-to-noise ratio lowered by the ping-pong-ball-
sized magnet (palm system) or the lossy on-chip coil (1-chip system). Second,
the new transceiver attains the highest level of integration among existing NMR
transceivers. The transceiver in the 2-kg portable system did not integrate a power
amplifier (PA), as meeting the large power tuning requirement of NMR was
nontrivial with an integrated PA. We integrate a PA in the new transceiver by
devising a power tuning scheme that exploits the natural high-Q (
10 4 ) filtering
ability of atomic nuclei.
We used our three miniature NMR systems to detect various kinds of
biomolecules relevant to disease screening. For example, we detected avidin, folic
acid, and human chorionic gonadotropin (hCG), which can be used as a cancer
marker for male patients for cancers such as choriocarcinoma, germ cell tumor, and
islet cell tumor. At the cell level, we detected human bladder cancer cells.