Seminar by Dr. Nguyen Si Hoai Vu, MSc. Nguyen Tuan Anh and Dr. Le Duy Manh

At 2:00 p.m. on June 20, 2025, IAST organized an academic exchange session at Meeting Room B - Tan Phong Campus and the Office of the Institute of Advanced Technology in Hanoi - Room 604 with the following detailed content

1/ Dr. Nguyen Si Hoai Vu presented on "Study on the fabrication of nano-structured bismuth oxide electrocatalysts for oxygen evolution reaction (OER) electrodes in water electrolysis"

Abstract:

The sluggish kinetics of the oxygen evolution reaction (OER) in water electrolysis remain a critical barrier to efficient and cost-effective clean hydrogen production, particularly in acidic proton exchange membrane (PEM) electrolyzers. Existing precious metal catalysts like IrO2 and RuO2 are prohibitively expensive and scarce, necessitating earth-abundant alternatives. This study addresses this urgent need by investigating the fabrication of highly active and stable nano-structured bismuth oxide (Bi2O3) electrocatalysts for OER electrodes. Bi2O3 is a promising candidate due to its abundance, low cost, low toxicity, and interesting electrochemical properties, including high oxygen vacancy density and ion conductivity. The core scientific idea is to enhance Bi2O3’s phase stability and catalytic performance through strategic doping with Zr and Ce and by engineering thin-film, nanoscale structures to increase active sites and improve charge transfer. Our research employs a systematic approach combining experimental synthesis with quantum mechanical DFT simulations. We will synthesize undoped and doped Bi2O3 thin films via spin-coating on titanium foil, optimizing fabrication parameters to control morphology and crystal structure. Comprehensive material characterization will establish structure-property relationships. Electrochemical performance for OER, including activity and long-term durability in acidic media, will be rigorously evaluated. DFT calculations will provide insights into electronic structure and catalytic mechanisms. This work significantly contributes to developing efficient, non-precious metal OER catalysts crucial for promoting sustainable hydrogen technologies. Exploring nano-structured Bi2O3 for OER in strong acidic environments remains a relatively new direction with significant gaps.

2/ MSc. Nguyen Tuan Anh presented on "Design, Fabrication, and Characterization of a MEMS-based Thermopile Sensor for Gas Flow Measurement"

Abstract:

This presentation details the development of a Micro-Electro-Mechanical Systems (MEMS)-based thermopile sensor designed for precise gas flow measurement. The sensor operates on the Seebeck effect, converting temperature differences induced by gas flow into a measurable voltage. We will discuss the comprehensive design methodology, including the structural configuration of the thermopile elements and the integrated micro-heater, optimized through COMSOL Multiphysics® simulations to enhance sensitivity and response time. The presentation will cover the photomask design and the detailed microfabrication process steps, involving silicon wafer processing, thin-film deposition for thermoelectric materials and heater, photolithography, and etching techniques (DRIE and KOH wet etching) to realize the membrane structure crucial for thermal isolation.

Furthermore, we will present simulation results illustrating the temperature distribution profiles across the sensor under varying gas flow rates and input voltages. Experimental results from the fabricated and packaged sensors will be shared, demonstrating the device's performance in detecting gas flow. This work highlights the potential of MEMS thermopile technology for developing compact, efficient, and reliable gas flow sensors for various industrial and research applications, moving beyond basic classroom concepts to practical device implementation and characterization.

3/ PhD. Le Duy Manh presented "Wavelet Analysis of Cardiac Signals: Prediction of Self-Terminated Ventricular Tachycardia in isolated rat heart experiments"

Abstract:

This study investigates whether self-terminating and prolonged ventricular tachycardia (VT) can be differentiated using cross-wavelet analysis. VT is a type of arrhythmia that may persist or transform into other arrhythmias. In this study, 40 VT samples from 7 isolated rat hearts were analyzed, including 19 prolonged VTs and 21 self-terminating VTs (STVTs). Bivariate time series of left ventricular and right atrium are analyzed using cross-wavelet analysis to find correlations between the signals. The results show that self-terminating VT occurs most often when there is a weak correlation between the signals, while prolonged VT is associated with a strong correlation between ventricular and atrial signals. The study suggests that mechano-electrical interaction between the right atrium and left ventricle may be the underlying mechanism for this connection. The findings may have implications for understanding the underlined mechanism and treatment of VT in clinical practice.