Owing to the fast development of small-power portable electronics, the requirement on micro power sources with low cost and high energy density is more and more stringent. However, conventional primary and secondary battery technologies are currently facing a hysteretic development of their energy density, calling for new electrochemical energy storage and conversion devices. Among them, miniaturized fuel cells, metal-air batteries and non-Lithium ion batteries are receiving more and more interest. Our research work is closely related to this specific field, including micro fluidic fuel cells, paper-based metal-air batteries and Al ion battery. In this talk, a fuel-breathing micro fluidic fuel cell utilizing volatile hydrocarbon fuels or hydrogen gas will be introduced first, demonstrating its superiority in high fuel utilization, operation robustness and stacking efficiency. Techniques for inhibiting the cathode flooding problem will also be presented. Moreover, a paper-based micro fluidic fuel cell prototype will be demonstrated with much simplified operation condition. In addition to fuel cells, an innovative Al-air battery utilizing paper-based micro fluidics will also be presented and discussed, which can achieve simplified battery system, inhibited Al corrosion together with lowfabrication cost. Targeted for different application fields, three battery designs have been proposed, including the rechargeable battery for charging portable electronics, the flexible battery for powering single-use devices, and the printable battery for coupling with existing printing techniques. Finally, a preliminary study on a flexible and printable Al ion battery will be introduced.

Dr. Yifei Wang received his B.Sc. degree from Department of Modern Mechanics, University of Science and Technology of China in 2012, and his Ph.D. degree from Department of Mechanical Engineering, the University of Hong Kong in 2016. He is currently a Postdoctoral Fellow in the University of Hong Kong. His research interest is mainly focused on micro fluidic fuel cells, paper-based metal-air batteries and Al ion batteries, including both experimental study and numerical investigation. During the past five years, he has published 30+ journal papers and obtained two patents in the relevant fields. His future research will be focused on flexible and printable thin-filmpower sources for various portable and wearable electronics, including fuel cells, metal-air batteries, metal ion batteries, etc.