SKIN COLOR MONITORFinal Design ReportDecember 12, 2008Team:Amy Lenz, Vincent Mi, Brooke Sampone, Grant SmithAdvisor:Walter F. Block, Ph.D.Client:John G. Webster Ph.D.Skin Color Monitor: Final Design Report! 1TABLE OF CONTENTSAbstract! 3Problem Statement! 3Motivation! 3What Already Exists! 4Current Devices! 4Previous Semesters’ Work! 5Design Criteria! 6Design Alternatives! 7Light sources! 7Light Detectors! 7Housing Considerations! 8Circuit Considerations! 9Final Prototype! 10Final Design! 10Cost analysis! 10Testing! 11Future Work! 12Product Design Specifications! 15Skin Color Monitor: Final Design Report! 2SKIN COLOR MONITORFinal Design Repor"AbstractMenopausal women commonly experience discomfort due to hot flashes. The objective was to develop a device that detects hot flashes by measuring changes in skin redness. The prototype uses a 525 nm LED to illuminate the skin and a photodiode in photovoltaic mode to detect the reflected light. The output signal from the photodiode is amplified through an inverting amplifier with a low pass filter. As expected, the device observes decreasing skin reflectance with increasing skin flushness. The device consistently output a decrease of 5-10 mV between flushed and normal skin. This semester’s work focused on minimizing the size and weight of the device through a complete re-fabrication of the LED/photodiode housing as well as a semi-permanent soldered circuit. Problem StatementThe goal is to improve upon an already existing skin color monitor. The device uses a colored LED and a photodiode to detect color changes in women’s skin color due to hot flashes. The purpose of the device is to record sudden color changes resulting from hot flashes for analysis during research and testing of pharmaceutical menopausal drugs. Compliance with FDA standards is also important, because the device is meant to be worn continuously to optimize the amount of data that can be recorded. As a result, the device needs to be small and aesthetically pleasing or to be concealed under clothing. Continuous use requires the device to run on a battery that will last for at least one day while readings are recorded every ten seconds. To properly detect hot flashes, the device needs to be worn on the chest or upper arm region where significant blushing has been frequently observed (James et al., 2004). Overall, the device needs to be compact (less than 6 cm x 6 cm x 1 cm), comfortable and inexpensive (less than two-hundred dollars to manufacture, disposable parts are desired to cost under seven dollars).MotivationMiddle-aged women commonly experience hot flashes as a symptom of menopause. Hot flashes are characterized by a sudden onset of warmth, skin redness, and sweating. During menopause, the depletion of primary oocytes cause follicle stimulating hormone (FSH) to respond to the cease of ovarian and uterine cycles. Consequently, lowered levels of estrogen and progesterone confuse the hypothalamus, causing the body to register at a higher temperature than normal (Martini, 2006). To compensate for this illusion of high body temperature, the heart increases blood flow and blood vessels dilate to allow saturation of capillary beds. The elevated blood flow in epidermal capillary beds causes the visually observed flushness. As a result, heat is lost from the surface of the skin which is meant to lower the body temperature.Skin Color Monitor: Final Design Report! 3Over fifty percent of women in Western cultures experience hot flashes during menopause. In contrast, Eastern cultures such as China, Japan and Pakistan have hot flash occurrence rates below twenty percent. The significant decrease is thought to be due to the presence of dietary phytoestrogens, which are found in soy and mimic the chemical properties of estrogen. (WebMD Health, 2000)A device to help monitor hot flash occurrence would help in diagnosing hot flashes as well as quantifying the effectiveness of any drug treatments. Current methods of logging hot flash occurrence are qualitative, unreliable, and prone to human error. This new device aims to provide a reliable quantitative solution to this problem. This will allow for quantitative analysis of hot flash frequency, intensity, and duration. Identification of these factors allows for a better understanding of hot flashes and treatments.What Already ExistsC U R R E N T D E V I C E SSeveral existing devices are used to monitor hot flashes. Physicians currently rely on patients’ documentation of physical symptoms through a journal. Although this is a simple and cost effective way to monitor hot flashes, several problems are associated with this system. This data is unreliable as it is completely subjective and highly prone to human error.Produced by UFI, BIOLOG is a device currently on the market with the potential to monitor hot flashes (Figure 1). This multipurpose device can be programmed to monitor hot flashes by measuring various physiological properties. However, this device lacks many desired qualities. The market price of the device is about $2200 and the software required for analysis is an additional $2000. Also, the device is too large and bulky, weighing approximately 200 grams. These factors make the BIOLOG undesirable for the given application.The client has already developed a device to monitor hot flashes through skin conductance (Figure 2). This device employs electrodes attached to the skin to measure conductance. When the subject sweats, changes in the conductivity of her skin are measured and recorded. The subject is also asked to make note of hot flashes by manually swiping a magnetic indicator over the device. Although this device can accurately measure hot flashes, the client hopes to monitor hot flashes through a different variable: skin color.Skin Color Monitor: Final Design Report! 4Figure 1. The BIOLOG can be programmed to specifically monitor hot flashes in several di!erent ways. "Hot Flash, 2007#P R E V I O U S S E M E S T E R S ’ W O R KThis project is in its third semester of work. The first semester team designed the basic housing and setup of the skin color monitor. The housing was made of rigid, black
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