Abstract: With the development of emerging micro electronics devices with miniwatt or even microwatt power requirement, such as lateral flow testers, RFID tags and various biosensors, the development of associated micro power sources will be of key importance. Since these electronics gadgets will be produced in great quantity and widely applied, the cost and environmental impact of the associated power unit should be carefully considered. Conventional primary dry batteries and secondary Li ion batteries are either too hazardous or too expensive for this task, while both of them lack the continuous operation ability. Regarding this, the miniaturization of various green energy technologies, such as fuel cells, metal-air batteries and aqueous ion batteries, is getting more and more research interest. Fuel cells are well known for their uninterrupted operation as long as fuel and oxidant are provided, which are especially suitable for wearable healthcare sensors with long working time. To reduce their scale and cost, microfluidic fuel cell with no need for expensive polymer membrane electrolyte is a suitable strategy, whose performance can be greatly improved by tailoring the mass transport inside. Our group has proposed several methods to improve the fuel utilization, voltage output and discharge stability of microfluidic fuel cells, including the fuel-breathing anode, circular stacking and catalyst layer cracking technologies. Compared with fuel cells, metal-air batteries are well known for their higher voltage and lower fabrication cost, which are especially suitable for disposable electronic applications. To simplify the fluidic transport and hence system structure, our group has developed a series of paper-based metal-air batteries with high performance and energy efficiency, which utilize the capillary action of paper to deliver electrolyte passively. Furthermore, to deal with electronic devices with repeated usage, our group has also studied the rechargeable aqueous ion batteries, using low-cost Al or Zn metal as negative electrode directly. To lower down the water electrolysis side reaction within aqueous system, a super-concentrated “water-in-salt” electrolyte is employed and proved to be effective. Finally, various commercial printing technologies are utilized to achieve an intelligent manufacture of these microscale power sources together with great device flexibility.