Automated Device to Measure Forces and Frequency of Vibrations in Mosquito Bites Kevin Brosche and Jake Feala Department of Biomedical Engineering BME 400 Capstone Design Client Professor Amit Lal Department of Electrical Engineering Advisors Professors Willis Tompkins and Mitchell Tyler Department of Biomedical Engineering Problem Statement To design an automated device to sense and quantify forces and vibrations present in mosquito bites The motivation for building a device that does this is to examine how mosquitoes use their proboscis to bite in a way that is often virtually undetectable to humans The longterm goal is to design a needle that mimics this behavior in order to minimize discomfort in blood and fluid sampling Background on Mosquitoes Mosquitoes will be the test subjects for this research Therefore it is essential to understand their anatomy and behavior and in particular what attracts them There are more than 2400 species of mosquitoes about 150 of which originate in North America Commonly regarded as one of nature s biggest pests the mosquito has spawned a multi billion dollar industry in repellents to keep them away as well as attractants to attract and eliminate them Unlike most insects light has no significant attractive effect on mosquitoes Becker et al 1995 rather mosquitoes respond primarily to chemical attractants to locate their prey Because attracting mosquitoes to our device is critical to obtaining results we have extensively researched major mosquito attractants Carbon Dioxide CO2 exhaled during breathing is commonly regarded as the primary attractant for almost all mosquito species In addition numerous studies cite sweat extracts or chemicals exhaled in breathing as long range attractants 1 octen 3 ol and lactic acid are among the most rigorously studied and have been shown to act synergistically with CO2 to increase mosquito response Kline et al 1990 Healy Copeland 1995 Female mosquitoes are the only blood sucking or host seeking mosquitoes males lack the proboscis that is used to penetrate the skin It has been hypothesized that during bites mosquitoes vibrate their proboscis Sonic vibrations may alter the Young s modulus stiffness of the skin as perceived by the proboscis by the same physical concept that can make a liquid seem hard if its surface is struck by a fast moving object Therefore less force would be required in puncturing the skin and a smaller area on the skin would be deformed during the process This may be one reason a mosquito s bite oftentimes goes undetected by pain receptors in the skin Preliminary research shows vibrations in the range of 200 400 Hz may be produced during bites Prior Work A preliminary prototype has been designed that uses piezoelectric film PVDF to sense extremely small forces produced by the mosquito s proboscis The current device has promise but lacks the accuracy and consistency needed to draw conclusions from the data Constant monitoring is necessary to operate this prototype which requires hours of attention to capture a few bites A self contained automated unit would greatly accelerate this research The current sensor is shown below It will be described in the next section Device Components and Criteria Physical Environment The device needs to be self contained This means that all the electrical components and battery need to fit in a compact box that eventually may be placed outdoors For this reason the box must be watertight and designed to withstand moderate environmental elements Chemical Biological Physical Attractants Some method of attracting mosquitoes and inducing them to bite is required The device must attract mosquitoes in the vicinity of the box and persuade them to bite a sensor The device should utilize one or more known mosquito attractants including dark colors heat moisture CO2 lactic acid acetone 1 octen 3 ol sweat host odors natural skin scent These attractant methods have different effects at different ranges testing will be necessary to find the optimum combination Previous work found the most success with a combination of heat applied directly beneath the sensor CO2 and skin scent rubbed on the sensor just before introducing it to the mosquito Of the other attractants only 1 octen 3 ol has been tried albeit unsuccessfully when used on Anopheles mosquitoes However this may have to do with the way in which it was applied rather than its attractive promise Photodiode Motion Sensor Could be used to detect the presence of mosquitoes in the test chamber and activate the electronics for the possibility of a bite This is not a requirement but it could be very helpful for both conserving power and collecting only relevant data Sensor The sensor will build on previous work with piezoelectric polyvinyl diflouride PVDF film Two identical PVDF squares were mounted on a circuit board below small holes in a copper plate with room to vibrate in the z direction as shown below The active and ground electrodes copper traces on a printed circuit board were then connected to an AD620 in amp which acted as a differential preamplifier for the signal before being filtered and amplified on a different board then sent to a computer for processing The amplifier must have very high gain and common mode rejection ratio to accurately pick up the miniscule signals created by the mosquito bites Also a high pass filter is necessary to attenuate the high DC offsets and low frequency drift caused by changes in temperature and air pressure ground electrode active electrode bite hole PVDF The existing setup has brought some success but for accurate results improvements are needed Interference rejection must be improved low frequency drift must be attenuated further and the entire sensor must be more robust and consistent Data Logger The device must at the very least be able to record the force and frequency of biting over a period of hours then output the data to a computer for processing Ideally the device would also be able to do the analysis and display meaningful data though this is not currently a requirement Potential Solutions Physical Environment Compact plastic boxes are available in the BME Student Design Center that could easily be modified to house all electrical components and batteries Splitting the box into two pieces that could easily be taken apart would greatly facilitate the retrieval of data between tests and allow easy access to the electronics for repairs Chemical Biological Physical Attractants