Luwen Wang

Design, fabrication and testing of an air-breathing micro direct methanol fuel cell with compound anode flow field

An air-breathing micro direct methanol fuel cell (μDMFC) with a compound anode flow field structure (composed of the parallel flow field and the perforated flow field) is designed, fabricated and tested. To better analyze the effect of the compound anode flow field on the mass transfer of methanol, the compound flow field with different open ratios (ratio of exposure area to total area) and thicknesses of current collectors is modeled and simulated. Micro process technologies are employed to fabricate the end plates and current collectors. The performances of the μDMFC with a compound anode flow field are measured under various operating parameters. Both the modeled and the experimental results show that, comparing the conventional parallel flow field, the compound one can enhance the mass transfer resistance of methanol from the flow field to the anode diffusion layer. The results also indicate that the μDMFC with an anode open ratio of 40% and a thickness of 300 µm has the optimal performance under the 7 M methanol which is three to four times higher than conventional flow fields. Finally, a 2 h stability test of the μDMFC is performed with a methanol concentration of 7 M and a flow velocity of 0.1 ml min−1. The results indicate that the μDMFC can work steadily with high methanol concentration.

High-Frequency Modeling of On-Chip Coupled Carbon Nanotube Interconnects for Millimeter-Wave Applications

This paper presents a high-frequency equivalent circuit model for on-chip coupled carbon nanotube (CNT) interconnects up to 100 GHz. By simplifying the circuit model, the S-parameters of on-chip coupled interconnects can be acquired and validated by comparing with the full-wave electromagnetic simulations. By virtue of effective complex conductivity, the high-frequency behaviors of coupled CNT interconnects are captured and studied, with the impacts of kinetic inductance treated appropriately.

Modeling and optimization of single-turn printed coils for powering biomedical implants

A new coil optimization procedure is proposed for inductively coupled wireless power transfer when square single-turn printed coils are used, by means of analytically modeling the self- and mutual-inductances, parasitic resistances, and parasitic capacitances of these coils. As an example, the average diameter and trace width of the transmitting coil and the trace width of the receiving coil are optimized when the average diameter of the receiving coil and the transfer distance are assumed to be fixed. The efficiency is improved by 30% (i.e., form 40% to 70%) in comparison with the existing optimization method.

Design and fabrication of a novel portable passive DMFC stack

We designed and fabricated a new portable passive DMFC stack with its volume significantly reduced. Its high efficiency and load regulation performance were also demonstrated through experiments, and its stability seemed to be very good. We achieved a maximum power density of 3.9mW/cm2 with a 2M methanol concentration under ambient conditions. This performance is better than that of a conventional DMFC. The volume of the 10-cell series connection DMFC stack is only 42mm x 42mm x 40mm. Due to its stable performance and easy fabrication, this structure is believed to be applicable for portable small-scale DMFC stack.