Engineering evaluations and studies. Volume 3: Exhibit C

High rate multiplexes asymmetry and jitter, data-dependent amplitude variations, and transition density are discussed

The development of an electrochemical sensing device for controlled drugs.

Forensic chemists can be faced with a wide array of substances to test when attending clandestine drug manufacture crime scenes. Whilst many techniques exist at their disposal - such as chemical colour test reagents and immunoassays - these methods are at best semi-quantitative and often subject to false positives. Electrochemical methods of detection offer a potential solution to this problem, as the equipment is portable, cheap and robust. The analysis is quantitative and, if the electrode/electrolyte combination is designed properly, it can be extremely sensitive and selective. The scientific literature contains many examples of voltammetric analyses of controlled drugs. A square wave voltammetric analysis of the novel psychoactive substance benzyl-piperazine is reported here, representing the first time this analysis has been established. A limit of detection of 6 μM was achieved, and resolution against the similar ecstasy-type drug 3-4-methylenedioxymethylamphetamine (MDMA) was demonstrated. Two innovative USB powered prototype potentiostats have been developed. As proof of concept, an ATMega328P microcontroller was used in conjunction with 12-bit digital-to-analog and analog-to-digital converters (MAX532 and MCP3304 respectively). Using ferricyanide for redox at a glassy carbon electrode, reversible cyclic voltammetric analyses and square wave linear calibration (2.7 to 13.7 μM, R2=0.998) were achieved by the first prototype. The second prototype extended the compliance range (from ±2.5 V to ±12 V) and improved the signal to noise ratio. The second prototype also achieved a linear calibration using square wave voltammetry of MDMA (41 to 82 μM, R2=0.995) at a carbon paste electrode

Implantable Piezoresistive Microcantilever-based Wireless Cocaine Biosensors

Cocaine is a well-known, illegal, recreational drug that is addictive due to its effects on the mesolimbic reward pathway in the human body. Accurate and real-time measurement of the concentration of cocaine in the body as a function of time and physiological factors is a key requirement for the understanding of the use of this drug. Current methods for such measurements involve taking samples from the human body (such as blood, urine, and hair) and performing analytical chemistry tests on these samples. This techniques are relatively expensive, time consuming, and labor intensive. To address this issue, a new implantable sensor for the automated detection and measurement of the relative cocaine concentration is presented here. The device is more economical and provides for higher sampling frequencies than the current methods. The active sensor elements consist of piezoresistive microcantilever arrays, which are coated with an oligonucleotide-based aptamer, i.e. a short sequence of RNA with high affinity for specific target molecules, as the cocaine receptor. A Wheatstone bridge is used to convert the biosensor signal into an electronic signal. This signal is transmitted wireless at an operating frequency of 403.55 MHz, which complies with the US Medical Implant Communication System (MICS) FCC 47CFR Part 95. The limit of detection for the in vitro experiment is found to be 1 ng/ml. The device has successfully measured the relative concentration of cocaine upon implantation in the subcutaneous interstitial fluid of male Wistar rats