Materials and Methods

1. Wireless Strain Sensors JeVaughn Julius, ObinnaIgwe, KaustubhShinde, SmithaRao, J.-C. Chiao Electrical Engineering Summer REU, The University of Texas at Arlington, Arlington, Texas 76019 Abstract A wireless strain sensor system has been designed to monitor and measure strain at any flexing region. The main focus is on measuring the strain caused on different regions of the body like the human finger and maybe the human stomach. The strain sensors are made with a laser system using 125-µm thick Kapton sheet, which is followed by an encapsulation process to package all the sensors in elastic poly-dimethylsiloxane known as PDMS which will be used to measure the strain of the flexing region. Introduction Strain sensors can be used to help measure the strain of the flexing region. By measuring the strain on muscles, doctors would easily be able to detect arthritis. Arthritis effects about 50 millions U.S. adults each year and expecting to grow up to 67 millions by the year 2030. With the strain sensors people with arthritis can get the proper help needed to determine how much they can actually bend with a special strain sensor glove that will measure the strain which will helps the doctors determine what is the next proper step to take to make the patient live better. Summary and Conclusions A strain sensor integrated with a wireless system to monitor and measure strain at any flexing region has been demonstrated. The main focus is on measuring the strain caused on different region of the body like the human finger and maybe the human stomach. Strain sensors can be used by doctors to help measure the strain of the flexing region which can be used to help people with arthritis for example which affect millions of peoples. With the strain sensors people with arthritis can get the proper help needed to determine how much they can actually bend their fingers with a special strain glove that will measure the strain. The sensor is not kept at the joint but instead a cut out Kapton sheet which is attached to the sensor is kept over the joint. When the finger is bent, this sheet bends. This stretches the sensor attached to the sheet and thereby gives a better sensitivity. The wireless strain sensor system architecture is capable of monitoring multiple patients and/or multiple sensors simultaneously. Results . dr/R vs dl/L% dr/R vs dl/L Day 5 Day 1 Figure 2: The slope shows the gauge factor of the sensor of the calculated dR/R and dL/L of the plotted graph. Materials and Methods To make the strain sensor we first start with 125-µm Kaptonsheet on which a layer of amorphous carbon is deposited. This process is done in a clean room which takes approximately 8 hours to do. Once the carbon Kapton is deposited, the next step is laser micromachining which is a 2 hour process to make using Alpha-Cam software. Once all sensors are made, the electrical connections are done so that the resistance across the sensor can be measured. Last each strain sensor is encapsulated in poly-dimethylsiloxane between 10 to 20%. The sensor is not kept at the joint, but instead a piece of Kapton sheet which is attached to the sensor is kept over the joint. When the finger is bent, the Kapton sheet bends. This stretches the sensor attached to the sheet and thereby gives a better sensitivity. dr/R vs dl/L Figure 5: Tested 3 sensors for sensitivity and maximum strains of Original Design (1mm width), Original Design (2mm width), and Two Triangle Design (1mm width). Literature cited Tata, Uday, Hung Cao, VaibhavLandge, Cuong M. Nguyen, and J.-C. Chiao. "Wireless Strain Sensor Based on Amorphous Carbon for Human-Motion Detection." N.p., 20-23 Jan. 2013. Web. 22 June 2013. "CDC - Chronic Disease - Arthritis - At A Glance." Centers for Disease Control and Prevention.N.p.,n.d.Web.28 July 2013. <http://www.cdc.gov/chronicdisease/resources/publications/aag/arthritis.htm>. Figure 3: The plotted graph show the Gauge Factor of the calculated dR/R and dL/L of one joint and three joints. B 2mm 1mm Acknowledgments We thank Dr. Kambiz Alavi and Mohammadreza Jahangir Moghadam for heading the REU Program along with Smitha Rao and J.-C. Chiao. We also thank NSF and UTA for funding and hosting the REU program. REU Site: Research Experiences for undergraduates in Sensors and Applications at University of Texas at Arlington 0.5mm 1.5mm 1mm 0.5mm B D F Figure 6: Tested the repeatability of the sensors. Further Information Figure 4: Designs of different strain sensors for better sensitivity with different width. Figure 1: A encapsulated sensor in poly-dimethylsiloxane (PDMS). Contact JeVaughn Julius (juliusj@uta.edu) or Smitha Rao (smitha@uta.edu).