Alan Young, Dr. Weidong Zhou and Dr. Hongjun Yang

1. Nanomembrane Pressure Sensing System Alan Young, Dr. Weidong Zhou and Dr. HongjunYang Department of Electrical Engineering, The University of Texas at Arlington, Arlington, Texas 76019 Abstract The goal of this project was to develop a distributed pressure sensing system to provide a 3D pressure contour map. It will be used to measure the force of a stamper being applied to a thin film. Operating instructions for building the system and operating the LabVIEW program will be provided to other graduate students for future use. Designs for full pressure sensing systems using other commercial companies will also be conducted to find the best way to provide a 3D pressure map. • Results • This project’s premise for developing a nanomembrane pressure sheet using LabVIEW was to help Dr. Zhou’s research group find a way to plot the pressure distribution created when stamping thin films. • I conducted an initial overview of different parts from various vendors and came up with an estimate of what the cost of a pressure sensing sheet would be. The result turned out to be very expensive. • $10,000 to $15,000 • Many companies came with their own software • Needed an inexpensive way to create a pressure sensor sheet that could be used with LabVIEW • After deciding on a cheaper vendor and buying the parts, several things were achieved: • Design of various pressure sensing systems. • A 4 point pressure sensor system with a maximum error of about 20% • Creation of a LabVIEW program to view the different pressures of each sensor in real time • Several general observations derived from the experiments that are important for developing a smaller and more sensitive pressure sheet: • The output of each sensor must be grounded in order to ensure accurate measurements. • Trying to create a very small pressure sensor sheet with thousands of sensors would not be feasible using a LabVIEW DAQ due to the limited number of inputs that each Data Acquisition Board has. • The smallest value for each sensor was about 1 lb, or about 500 grams. Smaller weights and more sensitive pressure sensors will be required for the nanomembrane pressure sheet. • The error for each sensor was different, requiring a calibration for each. Summary and conclusions I was able to achieve a 3D pressure distribution plot using LabVIEW. However, the accuracy of the measurements were limited by the sensitivity of the pressure sensors, the data acquisition rate of the DAQ, and the limited size and number of the pressure sensors. Applying this research to stamping thin films would be a challenge mainly in manufacturing the small pressure sensors required for a pressure sensing sheet. Constructing small pressure sensor-like pixels is very expensive, which explains why companies charge $10,000-$15,000 for pressure sensor sheets that have a greater resolution in their pressure mapping systems. More comparisons must be done with commercially available pressure mapping systems in order to find the lowest cost. If possible, small pressure sensors could be made at the Nanofabrication building, but a Data Acquisition Board would not be the best way to measure the value of more than four pressure sensors at once. Introduction A nanomembrane pressure sensing system is needed in the nanofabrication building for quality control in stamping thin films. Currently, nonuniformities are created when stamping by hand, which causes the thin films to stick to the stamper. My objective was to design, build, and program a pressure sensing system to create a 3D contour plot on a computer, and find ways in which my system can compare to a pressure sensing system that is commercially manufactured. Figure 2. LabVIEW program used to plot the 3D pressure plots. Materials and methods 4 Tekscan Flexiforce sensors as well as 4 FlexiforceQuickstartBoards were used. A National Instruments 9201 Data Acqusition Device was connected to a National Instruments cDAQ 9171 to read analog voltage signals from the Quickstartboards. An Agilent E3610A Power Supply was also used to ground the signals from the FlexiforceQuickstart Boards. LabVIEW 2011 was used to program the system. Figure 3. 3D pressure plots of the sensors, before any weight was applied. Acknowledgments I would like to thank Weidong Zhou, Hongjun Yang , KambizAlavi, Jonathan Bredow, and Mohammadreza for their unwavering support these past 9 weeks. This research would not be possible without the NSF grant # EEC-1156801,  REU Site: Research Experiences for Undergraduates in Sensors and Applications at the University of Texas at Arlington For further information Please contact ayoung@uta.edufor more information on this project and related projects. Figure 4. 3D pressure plots of the sensors, with differing pressure on each sensor. Figure 2. Illustration of important piece of equipment, or perhaps a flow chart summarizing experimental design. Scanned, hand-drawn illustrations are usually preferable to computer-generated ones. Figure 1. The experimental set up for the pressure sensor sheet. Four 9V batteries were used to power four circuit boards which converted the resistance change of the pressure sensors to an analog voltage, which were read by the Data Acquisition Board.