WEARABLE BIOSENSOR
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INTRODUCTION
Now a days an affordable health care is needed to a person at any place & at any time. Wearable sensors and systems have evolved to the point that they can be consider ready for clinical application. The use of wearable monitoring devices that allow continuous or intermittent monitoring of physiological signals is critical for the advancement of both the diagnosis as well as treatment of diseases.
Wearable systems are totally non-obtrusive devices that allow physicians to overcome the limitations of ambulatory technology and provide a response to the need for monitoring individuals over weeks or months. They typically rely on wireless miniature sensors enclosed in patches or bandages or in items that can be worn, such as ring or shirt. The data sets recorded using these systems are then processed to detect events predictive of possible worsening of the patient’s clinical situations or they are explored to access the impact of clinical interventions.
Wearable systems for health monitoring need to satisfy a great variety of criteria and constraints. These include small weight and size, privacy of medical data, unobtrusiveness, ease of use, low cost , reliability & low power consumption. So designing such system is very difficult. In this we are considering basically two types of sensors – ring sensor & smart shirt . Ring sensor is a pulse oximetry sensor that allows one to continuously monitor heart. The device is shaped like a ring and thus it can be worn for long periods of time without any discomfort to the subject. The applications of ring sensor are catastrophic detection, chronic medical conditions etc. Smart shirt developed at Georgia tech which represents the first attempt at relying an unobtrusive, mobile and easy to use vital signs monitoring system. The principal advantage of smart shirt is that it provides for the first time a very systematic way of monitoring the vital signs of humans in an unobtrusive manner. The applications of smart shirt are medical monitoring, space experiments, mission critical hazardous application, fire- fighting, wearable mobile information infrastructure.
WEARABLE BIOSENSOR – RING SENSOR
Ring sensor is a pulse oximetry sensor that allows one to continuously monitor heart rate and oxygen saturation in a totally unobtrusive way. The device is shaped like a ring and thus it can be worn for long periods of time without any discomfort to the subject. The ring sensor is equipped with a low power transceiver that accomplishes bi-directional communication with a base station, and to upload date at any point in time.
Basic Principle Of Ring Sensor
Each time the heart muscle contracts, blood is ejected from the ventricles and a pulse of pressure is transmitted through the circulatory system .This pressure pulse when traveling through the vessels, causes vessel wall displacement which is measurable at various points. In order to detect pulsate blood volume changes by photoelectric method, photo conductors are used. normally photo resistors are used, for amplification purpose photo transistors are used.
Light is emitted by LED and transmitted through the artery and the resistance of photo resistor is determined by the amount of light reaching it. With each contraction of heart, blood is forced to the extremities and the amount of blood in the finger increases. It alters the optical density with the result that the light transmission through the finger reduces and the resistance of the photo resistor increases accordingly. The photo resistor is connected as a part of voltage divider circuit and produces a voltage that varies with the amount of blood in the finger. This voltage closely follows the pressure pulse.
Working Of Ring Sensor
The LEDs and PD are placed on the flanks of the finger either reflective or transmittal type can be used. For avoiding motion disturbances quite stable transmittal method is used. Transmittal type has a powerful LED for transmitting light across the finger. This power consumption problem can be solved with a light modulation technique using high-speed devices. Instead of lighting the skiing continuously, the LED is turned ON only for a short time, say 10-100 ns, and the signal is sampled within this period, high frequency, low duty rate modulation is used for preventing skin-burning problem.
SMART SHIRT (WEARABLE MOTHERBOARD)
Smart shirt developed at Georgia tech which represents the first attempt at relying an unobtrusive, mobile and easy to use vital signs monitoring system; presents the key applications of the smart shirt technology along with its impact on the practice of medicine; and covers key opportunities to create the next generation of truly “adaptive and responsive” medical systems.
Research on the design and development of a smart shirt fort a combat casualty care has led to the realization of the world’s first wearable motherboard or an “intelligent” garment for the 21st century. The Georgia tech wearable motherboard (GTWM) uses optical fibers to detect bullet wounds and special sensors and interconnects to monitor the body vital signs during combat conditions. This GTWM (smart shirt) provides an extremely versatile framework for the incorporation of sensing, monitoring and information processing devices. The principal advantage of smart shirt is that it provides for the first time a very systematic way of monitoring the vital signs of humans in an unobtrusive manner.
Requirements Of Smart Shirt
Casualties are associated with combat and sometimes are inevitable. Since medical resources are limited in a combat scenario, there is critical need to make optimum use of the available resources to minimize the loss of human life, which has value that is priceless. In a significant departure from the past, the loss of even a single soldier in a war can alter the nations engagement strategy making it all the important to save lives.
- Similarly on the civilian side, the population is aging and the cost of the health care delivery is expected to increase at a rate faster than it is today. With the decreasing number of doctors in rural areas, the doctor/patient ratio is in certain instances reaching unacceptable levels for ensuring a basic sense of security when they leave the hospital because they feel “cutoff” from the continuous watch and care they received in the hospital. This degree of uncertainty can greatly influence their postoperative recovery. Therefore there is a need to continuously monitor such patients and give them the added peace of mind so that the positive psychological impact will speedup the recovery process
ARCHITECTURE OF SMART SHIRT
The GTWM was woven into a single –piece garment (an undershirt) on a weaving machine to fit a 38-40” chest. The plastic optical fiber (POF) is spirally integrated into the structure during the fabric production process without any discontinuities at the armhole or the segments using a novel modification in the weaving process.
An interconnection technology was developed to transmit information from (and to) sensors mounted at any location on the body thus creating a flexible “bus” structure. T-connectors –similar to “button clips” used in clothing are attached to the fibers that serve as a data bus to carry the information from the sensors (ex: ECG sensors) on the body.
The sensors will plug into these connectors and at the other end similar T connector will be used to transmit their information for monitoring equipment or DARPS (Defense Advanced Research Projects Agency) personnel status monitor .By making the sensors detachable from the garments, the versatility I\of the Georgia Tech Smart Shirt has been significantly enhanced. Since shapes and sizes of humans will be different, sensors can be positioned on the right locations for all users and without any constraints being imposed by the smart shirt can be truly “customized”. Moreover the smart shirt can be laundered without any damage to the sensors themselves.