(Invited) Recent Advances on Energy Conversion Using Microfluidic Fuel Cells Technology, Case: Glucose Membraneless Micro Fuel Cell Stack

In recent years the microfluidic fuel cells (μFFC) have emerged as a promising solution for small-scale power demands (e.g., cell phones, sensors, biomedical devices and medical implants).  µFFCs are fed by liquid fuels and oxidants under laminar flow regimen; their principal goal is a longer operational time without frequent recharging. µFFCs operate without a physical barrier to separate the anode and the cathode, which implies the use of fewer components than conventional micro-direct PEM fuel cells and consequently their simplest operation and low maintenance events. The design of µFFCs must consider the optimization of size, weight and lifetime to improve the power supply for portable applications.

Different µFFCs generations have been already developed by our group in the last years with a tendency to reduce the cell size and channel dimensions. The first µFFC generation uses a “Y” shape channel and was constructed using a hot-pressing technique onto a PMMA [poly(methyl methacrylate)] plate to form the channel base.  In the second µFFC generation the use of micro-fabrication technology became an important tool in order to reduce the dimensions; the assembly consisted in a silicone polymer microchannel sandwiched between two SU-8 current collectors with a “T” configuration. The third µFFC generation simplifies the fabrication process and reduces significantly the costs by substitution of SU-8 material with a cellulose acetate film. The main modification of this generation resides on the integration of an air-exposed electrode as cathode enabling oxygen delivery directly from air (air-breathing). Furthermore, the substitution of 3-metal sputtering deposition by a single thin carbon film in direct contact with the catalytic material. This device that uses formic acid as fuel, is capable to achieve up to 29 mW cm^-2 of power density, which is the highest value reported to date.