This paper presents the first parylene-based floating-disk microvalve with self-pressure-regulating characteristics for various microfluidic applications. By incorporating a free-floating disk diaphragm with no anchoring/tethering structures to constrain its movement, the microvalve realizes configurable pressure-based flow-shunting functions in a stand-alone fashion. Its passive operation eliminates the need for power sources or the external actuation of the device. A multilayer polymer surface-micromachining technology is utilized for device fabrication by exploiting parylene C (poly-chloro-p-xylylene) as the biocompatible structural material for high mechanical compliance as compared with other conventional thin-film materials. Experimental results successfully demonstrate that the in-channel microvalves control water flows in the following two different shunt designs: 1) a nearly ideal regular check valve with zero forward-cracking pressure, zero reverse leakage, and 1.25 times10¹³ - 2.09 times 10¹³ Nldrs/m⁵ (0.03-0.05 psildrmin/muL, 1.55-2.59 mmHgldrmin/muL) of fluidic resistance; and 2) a pressure-bandpass check valve with 0-100 mmHg and 0-10 muL/min of pressure and flow rate regulation ranges, respectively, as well as 4.88 ×10¹³ Nldrs/m⁵ (0.12 psi middotmin/muL, 6.08 mmHg middotmin/muL) of fluidic resistance in the forward conductive region. Such a biocompatible and implantable microvalve has the great potential of being integrated in microfluidic systems to facilitate effective microflow control for lab-on-a-chip and biomedical applications. [2008-0055].