ABSTRACT LI, JINGYAO. Wicking Behavior of Placed Blood Drops on Textile Surfaces (Under the direction of Dr. Stephen Michielsen). As frequently encountered physical evidence at a crime scene, bloodstains could provide vital information to help investigators reconstruct the crime scene. Most BPA studies have been performed on hard surfaces. Only a few have focused on the interaction of blood and apparel fabrics, and none of the studies carefully characterized the yarn and fabric structure. Thus this research investigated the wicking and drying behavior of placed blood drops on customized fabric surfaces. The interactions between yarn structure, fabric structure and bloodstain patterns were examined. Two types of human blood simulants were used in this study, artificial blood and porcine blood. The artificial blood was made according to a modified ASTM method with adjusted viscosity and surface tension that referenced the value of porcine blood. The fabrics used for experiments were produced with 100% cotton yarns. These yarns were provided by Cotton Incorporated and were spun with ring spinning, open-end spinning and Murata vortex spinning methods. The yarns were manufactured into 100epi×100ppi balanced plain-woven fabric, 130epi×70ppi unbalanced plain-woven fabric, and jersey knit fabric. A piece of fabric was mounted in a hoop and placed on balance, then a blood drop of 80µL volume was placed onto the fabric. The real-time weight was continuously recorded as it dried. Meanwhile a digital camera was used to record the blood wicking process and the videos were analyzed using imageJ software to measure stain area and circularity on each time point. Yarn and fabric structures were characterized. Blood viscosity, surface tension and hematocrit values were measured. Analysis of bloodstains showed that artificial bloodstains have a larger area than porcine bloodstains due to the absence of blood-cell-like particles in artificial blood. Both yarn structure and fabric structure affect bloodstain patterns. Blood wicks faster on jersey knit fabric than on plain-woven fabric. For the same fabric structure, the more uniform yarn structure, the more easily that blood wicks. For the same yarn type, blood wicks more easily on balanced woven structure than unbalanced structure. An equation was derived to calculate blood volume according to the yarn packing factor and bloodstain area. This equation is valid on plain-woven fabrics made of ring spun yarns and open-end spun yarns, and on jersey knit fabrics made of ring spun yarns, open-end yarns and Murata vortex yarns. The equation has a coefficient of variation of 9.7% for plain- woven fabric, and 13.2% for jersey knit fabric, which suggests the equation is applicable for estimation of blood volume from bloodstain size on fabric surfaces. © Copyright 2015 by Jingyao Li All Rights Reserved Wicking Behavior of Placed Blood Drops on Textile Surfaces by Jingyao Li A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Master of Science Textile Chemistry Raleigh, North Carolina 2015 APPROVED BY: _______________________________ ______________________________ Stephen Michielsen Nelson Vinueza Benitez Committee Chair ________________________________ Nancy Powell ii DEDICATION For my grandmother Xiuping, my mother Xiaoli, my father Xiping, and my friend Zachary VanEvery. iii BIOGRAPHY Jingyao Li comes from Xi’an, China. The early experience of her father’s working trip to Europe evoked Jingyao’s great interest and desire of studying abroad and experiencing western culture. After earning her bachelor’s degree in China, she came to America in 2013 and studied at NC State University to pursue a Master of Science degree in Textile Chemistry. iv ACKNOWLEDGMENTS First and foremost, I would like to thank my advisor, Dr. Stephen Michielsen for his guidance, support, patience and encouragement. He is a scholar and a gentleman with intelligence and wisdom who illuminated my voyage through life when it was shadowed by distractions and confusions. I would also like to thank the National Institutes of Justice for funding this project, and Cotton Incorporated for providing the yarns. Thanks to Xingyu for making all the fabrics needed for the experiments. Last, but not least, I thank my parents for their unconditional understanding and support. I also apologize for not being able to be around them as their only one child. v TABLE OF CONTENTS LIST OF TABLES ................................................................................................................ vii LIST OF FIGURES ............................................................................................................. viii CHAPTER1 INTRODUCTION ............................................................................................ 1 CHAPTER2 LITERATURE REVIEW ................................................................................ 4 2.1. BLOODSTAIN PATTERN ANALYSIS .................................................................... 4 2.2. WETTING AND WICKING ....................................................................................... 6 2.3. FABRIC AND YARN STRUCTURE ....................................................................... 17 2.4. PHYSICAL PROPERTIES OF BLOOD ................................................................. 30 2.5. SUMMARY ................................................................................................................. 32 CHAPTER3 EXPERIMENTAL WORK ........................................................................... 34 3.1. FABRIC PREPARATION ......................................................................................... 34 3.2. ARTIFICIAL BLOOD PREPARATION ................................................................. 36 3.3. PORCINE BLOOD ..................................................................................................... 37 3.4. SURFACE TENSION MEASUREMENT ................................................................ 37 3.5. VISCOSITY MEASUREMENT ............................................................................... 39 3.6. HEMATOCRIT VALUE ........................................................................................... 43 3.7. EXPERIMENTAL SETUP FOR BLOOD WICKING AND DRYING ................ 43 vi 3.8. IMAGE PROCESSING ............................................................................................. 45 3.9. YARN TWIST MEASUREMENT ............................................................................ 47 3.10. LINEAR DENSITY MEASUREMENT ................................................................. 48 3.11. SCANNING ELECTRON MICROSCOPE ........................................................... 49 3.12. FABRIC THICKNESS MEASUREMENT ............................................................ 51 3.13. DISPOSAL OF EXPERIMENTAL MATERIALS CONTAMINATED WITH PORCINE BLOOD ............................................................................................................... 53 CHAPTER4 RESULTS AND DISCUSSIONS .................................................................. 55 4.1. BLOOD CHARACTERIZATION ............................................................................ 55 4.2. BLOOD DRYING ON FABRIC ............................................................................... 57 4.3. YARN CHARACTERIZATION ............................................................................... 59 4.4. FABRIC STRUCTURE AND ITS EFFECT ON BLOODSTAIN PATTERNS ... 68 4.5. THE EFFECT OF DROP VOLUME ON BLOODSTAIN PATTERNS .............. 70 4.6. OBTAINING BLOOD VOLUME FROM BLOODSTAIN AREA ....................... 72 CHAPTER5 CONCLUSION ............................................................................................... 78 CHAPTER6 SUGGESTED FUTURE WORK .................................................................. 80 vii LIST OF TABLES Table 1: General differences in structure arising from the spinning processes28, 30 ............... 22 Table 2: Surface tension results obtained by drop weight and sessile drop methods37 .......... 30 Table 3: Range of viscosities obtained for porcine blood37 .................................................... 31 Table 4: Hematocrit values obtained for porcine blood37 ....................................................... 32 Table 5: Customized fabrics ................................................................................................... 35 Table 6: Porcine blood viscosity ............................................................................................. 56 Table 7: Artificial blood viscosity .......................................................................................... 56 Table 8: Average bloodstain area of plain woven fabric ........................................................ 59 Table 9: Average bloodstain area of jersey knit fabric ........................................................... 59 Table 10: Yarn twist ................................................................................................................ 61 Table 11: Yarn cross-section area and packing density .......................................................... 67 Table 12: Fabric thickness ...................................................................................................... 68 Table 13: Statistics of whether porcine blood wicks on fabric samples ................................. 69 Table 14: The mean values of area