07-12-2012, 04:14 PM
Bio-medical application using VLSI design
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Abstract--
Medical apparatus like pacemakers face a big drawback in their batteries charging and patients require frequent surgery to have these batteries replaced. To power these devices, body energy techniques may be employed. Some of the power sources are patient's heartbeat, blood flow inside the vessels, movement of the body parts, and the body temperature (heat).Here we have come up with a new proposal for the charging of the batteries with the help of human body temperature when the device is still in use. The basic idea is to create a low-power, low-voltage circuit for both controlling and switching the charging of the battery. A voltage gradient is created with respect to the change in temperature by the serially connected thermocouples. This voltage generated is used to charge the battery. An analog ASIC or VLSI circuit is used for controlling and switching the charging current. Lithium ion battery which is used to store the charge is used for its portable and bio-free nature.
INTRODUCTION
Human heart consists of Sinoatrial node (SA) called pacemaker generates electrical impulses, which are responsible for the contraction and expantion of heart.An artificial pacemaker is a small device that is placed under the skin near our heart to help control our heartbeat. People may need a pacemaker for a variety of reasons- mostly due to a group of conditions called arrhythmias, in which the heart's rhythm is abnormal. The battery is nothing short of essential in performing the pacemaker’s life sustaining function. The weak spot in the early pacemaker was the power source, which was incapable of providing adequate power to permit long-term pacing of the human heart. muscles. The batteries which were used earlier for charging the pacemakers had to be monitored in every interval of time and also their lifetime was limited to just two or three years. To overcome these shortcomings, we have arrived at a design which converts body heat into electricity and uses this electricity to charge low power devices.Production of heat in the body can create electricity. The applications of this proposal are not limited to pacemakers alone, but can be extended to charge glucosemeters, implantable cardioverter-defibrillator (ICD),
also in military, for soldiers in battlefields as personal battery chargers, medical sensors, displays, gun sights, and range finders etc.
BODY AS A SOURCE OF ENERGY
Thermocouples is used to sense the body heat.A thermocouple is a junction between two dissimilar metal that produce a voltage related to temperature difference this effect is know as seeback effect. Thermocouple converts the heat into the potential difference that can be used to charge the battery. Thousands of microscale semiconductor thermocouples will harness body heat to generate enough electricity to power implant pacemakers. It is thought to develop a thermoelectric power system based on temperature differentials in the human body.An innovation in thermoelectric materials (TMs) using nanoscale-based thin-film materials to convert body heat into electrical energy has been developed. The resulting power can be used to ‘trickle charge’ batteries for medium-power devices such as defibrillators, or to directly power low energy devices, such as pacemakers. These power systems have the potential to run for as long as 30 years and they may reduce the number of medical procedures needed for implant replacement throughout a patient's life, reducing costs and potential complications. Semiconductor materials that produce electrical energy as a result of differential temperatures between hot and cold surfaces of the material are used.
VLSI CIRCUIT
The pacemaker uses complimentary-metal-oxide silicon (CMOS)and other sensitive transitor devices in very-large-scale integrated circuits(VLSI) arrangements to result in very small(in cm or mm)units.. Manufacturers began using CMOS devices in pacemakers because of therir low power consumption. When CMOS devices are packaged onto VLSI chip,the functional unit they hold becomes more sensitive to radiation damage.Despite its poor analog properties compared to bipolar technology, the use of CMOS technology for analog functions is increasing. There are two reasons for this. The first reason is that, CMOS is now, by far the most widely available IC technology. Many more CMOS ASICs and CMOS standard products are now being manufactured than bipolar ICs. The second reason is that, increased levels of integration require mixing analog and digital functions on the same IC. This has forced designers to find ways to use CMOS technology to implement analog functions. Circuit designers, using new techniques, have been very successful in finding new ways todesign analog CMOS circuits that can approach the accuracy of bipolar analog designs.