  We present an optofluidic sensor based on an elastomeric two-dimensional (2D)
grating integrated inside a hemispherical fluid chamber. Laser beam is
diffracted before (reflection) and after (transmission) going through the
grating and liquid in the dome chamber. The sensing mechanism is investigated
and simulated with a finite difference time domain (FDTD) based electromagnetic
(EM) method. For experiment, by analyzing the size, power and shape of the 2D
diffraction patterns, we can retrieve multiple parameters of the liquid
including the refractive index, pressure and opacity with high sensitivity. We
demonstrate that glucose concentration can be monitored when mixed in different
concentrated phosphate buffered saline (PBS) solution. The free-solution
binding of bovine serum albumin (BSA) and anti-BSA IgG is detected with this
optical sensor. This low-cost, multifunctional and reliable optofluidic sensor
has the potential to be used as monitor of biofluid such as blood in
hemodialysis.
