An apparatus may include a first microfluidic valve coupled between a first reservoir and a fluid channel. The first microfluidic valve may include a fluid agitator to break a meniscus formed at an air-fluid interface and release fluid from the first reservoir into the fluid channel in response to an electrical signal. The apparatus may also include a second microfluidic valve coupled between a second reservoir and the fluid channel. Fluid from the first reservoir and fluid from the second reservoir mix in the fluid channel.