Publications
last updated October 2017
Copper and liquid crystal polymer bonding towards lead sensing
Taufique Z. Redhwan, Arif U. Alam, Yaser M. Haddara, and Matiar M. R. Howlader
Abstract: Lead (Pb) is a highly toxic and carcinogenic heavy metal causing adverse impacts on environment and human health, thus requiring its careful monitoring. In this work, we demonstrate integration of copper (Cu) film-based electrodes toward Pb sensing. For this, we developed a direct bonding method for Cu film on liquid crystal polymer (LCP) substrate for the first time using oxygen plasma treatment followed by low-temperature heating. The bonding is mediated by an intermediate oxide layer as confirmed by elemental analyses. A strong adhesion (683 g.cm-1) is obtained between Cu/LCP that may offer prolonged use of the electrode in real-world sensing without delamination. Anodic stripping voltammetry of Pb using Cu film shows a stronger current peak than sputtered Cu electrode, which implies the significance of our direct bonding approach. We also present electrochemical impedance that will enable modeling of integrated environmental sensors for on-site monitoring of heavy metals.
Direct bonding of copper and liquid crystal polymer
Taufique Z. Redhwan, Arif U. Alam, Massimo Catalano, Luhua Wang, Moon J. Kim, Yaser M. Haddara, and Matiar M. R. Howlader, published in Materials Letters, vol. 212, pp. 214−217, 2017.
Abstract: Copper (Cu) film bonded with polymer substrates offers better dimensional stability than that of deposited Cu especially in humid environment. However, poor adhesion is an issue in both cases. In this paper, we demonstrate a two-step, low temperature direct bonding technique for liquid crystal polymer (LCP) and copper (Cu) using oxygen plasma. The bonded interface showed high peel strength. This strong adhesion is due to the interdiffusion of Cu and carbon atoms into LCP and Cu film respectively. These phenomena resulted in three-dimensional metal clusters of Cu atoms and islands at the LCP/Cu interface, which gradually diffuse into the LCP. Interfacial elemental analysis reveals an intermediate oxide layer formation due to Cu2O and C=O.
A Neyman-Pearson Approach to the Development of Low Cost Earthquake Detection and Damage Mitigation System using Sensor Fusion
Proceedings of 21st IEEE Int'l Conference on Electronics Circuits and Systems, December 7-10, 2014, Marseille, France
Abstract: Damage mitigation of critical infrastructures onset of an earthquake is a very important matter. In our work, we developed an earthquake warning and protection system through P-wave sensing that detects earliest onset of an earthquake before damaging ground shaking occurs. Our approach captures P-wave using redundant channels (dual sensors) and minimizes the possibilities of false triggers from harmless, momentary ground shaking. The system comprises a piezoelectric detector and a digital three-axis silicon accelerometer. The core of this study focuses on the detection algorithm using the collected data to decide if an earthquake is occurring. The algorithm is adaptive and is based on a probabilistic approach over a sliding window to maximize the detection of events, keeping the probability of false alarms under a fixed rate. Finally experimental results are provided showing the system meets the expected performance with both artificial and real seismic stimuli. One possible extension of our approach could be implementing geological wireless sensor networks using contemporary smartphones for data acquisition.