The invention provides hydrogel compositions, components, and hydrogel-actuated or mediated devices, and methods for the incorporation of hydrogel microscale components in microscale devices and systems. The methods and devices result in active microvalves that are useful in microfluidic applications, including analyte sensing, in process chemical and fermentation stream monitoring, and drug delivery. In particular, the devices are useful for controlled drug delivery either in response to a pre-determined stimulus or for pulsatile delivery.