  Cellular metabolic rate is a good indicator of the physiological state of
cells and its changes, which can be measured by total heat flux accompanying
metabolism. Chip calorimeters can provide label-free and high throughput
measurements of cellular metabolic rate, however, lack of high power resolution
and microfluidic sample handling capability has been preventing their wide
applications. We report high-resolution chip calorimeters integrated with
thin-film parylene microfluidics, which can reliably measure metabolic heat
from mammalian cells with controlled stimuli. The molding and bonding technique
allowed fast and reliable parylene microfluidic channel fabrications and highly
sensitive vanadium oxide thermistor enabled temperature resolution as small as
~ 15 {\mu}K, which led to a three-orders-of-magnitude improvement in volume
specific power resolutions. Measurements of metabolic heat were successfully
demonstrated with adherent and nonadherent cells. We expect the chip
calorimeter will provide a universal platform for fundamental cell-biology
studies and biomedical applications including cell-based assay for drug
discovery.
