This Small Business Innovation Research (SBIR) Phase II project aims to use digitally controlled vapor generators for calibration and test of explosive. Two systems will be created: a research oriented system, targeting manufacturers, for development of new explosive vapor trace detectors and production quality control and a portable system, intended for end users, for field testing and calibration. The use of digitally controlled ink-jet dispensing to precisely eject minute amounts of dilute explosive solutions and convert them into vapor has been demonstrated. We have also identified unique requirements of distinct vapor trace detector models and the actual needs of the marketplace. This project will: design and fabricate the two systems; generate the software control program; formulate explosive solutions customized for commercial explosive vapor trace detectors; develop test protocols for each system; evaluate the systems with commercial vapor trace detectors; and run reliability and repeatability testing. The research performed will also include: material compatibility studies; distribution of various explosive vapors by flow simulations and measurements; shelf life studies of the cartridges; and development of methods to calibrate the cartridges for explosive solutions.
The broader impact/commercial potential from this technology will be a method to evaluate the development of the next generation detectors. This project will lead to products (vapor generator systems and associated consumables). These products will provide the means to compare the various explosive trace detectors and to identify the most accurate ones. Ultimately, the ability to further miniaturize the vapor generators will lead to units that are embedded into next generation detectors for real-time verification and calibration. The overall societal benefit of successfully developing vapor generator products will be improved protection of the public, both real and perceived, from terrorist threats while minimizing the cost and negative perception related to false alarms. Technological advances from this project will facilitate basic research on detection mechanisms for explosives, drugs and chemical threats. Researchers in government labs and academia will be able to use the vapor generator to evaluate and quantify improvements of promising detection methods. The technology also has spin-off opportunities in olfaction based medical diagnostics.
Systems capable of detecting minute amounts of illicit substances are required in the airports, border crossings and high security areas. Explosives represent one important subclass, with the military explosives (TNT, RDX, PETN, HMX) being a subclass that is currently targeted by the various trace detection methods. Trace detection – detection of very small amounts – identifies people or things that have come in contact with explosives and was implemented in a variety of instruments, from handheld and portable to bench top or portals. Thousands of explosive vapor trace detectors deployed in the field require frequent verification and calibration to guarantee proper operation. Manufacturers require a method to evaluate the development of the next generation detectors, but existing technology cannot provide this. The developed vapor generators satisfy these currently unfulfilled but urgent needs and allow comparisons between various explosive trace detectors. The overall societal benefit of successfully developing vapor generator products is improved protection of the public, both real and perceived, from terrorist threats while minimizing the cost and negative perception related to false alarms. The technological advances facilitate basic research on detection mechanisms for explosives, drugs and chemical threats. Researchers in government labs and academia will be able to use the vapor generator to evaluate and quantify promising detection methods. The technology has spin-off opportunities in olfaction based medical diagnostics and drug delivery systems. MicroFab’s developments employ digitally controlled precision micro-dispensing technology to precisely eject minute amounts of dilute explosive solutions and convert them into vapors. An electrical pulse applied to a piezoelectric ink-jet micro-dispenser causes a drop of fluid to be ejected. These droplets land on a heater that converts them to vapor (Figure 1 and Figure 2). The amount of explosive delivered to the detectors can be controlled by the number of drops (dose mode – specified number of drops is generated) and the frequency of the droplet generation (continuous mode – droplets are generated continuously at fixed frequency). An additional control of the amount of explosive is provided by the concentration of the explosive solution that is dispensed facilitating the generation of infinitely small amounts of explosive vapors. The dynamic range of a vapor generator based on ink-jet microdispensers extends from almost zero (equivalent of several drops) to several thousands of parts per trillion and it can be changed digitally. MicroFab had a successful collaboration with the National Institute of Standards and Technology (NIST) and several manufacturers and users of explosive vapor trace detectors. The interactions established the desired functions and requirements. Several digitally controlled systems ranging from a bench-top/research instrument to a portable unit using ink-jet technology were prototyped and tested. The portable system has the ability to program temperature profiles (from adjustable constant values) with a very fast response heater (hundreds of degrees Celsius per second) and its control board (Figure 3). The very short ramp times of the heater can be used in other applications. Testing of the vapor generation technology indicated the ability to generate vapors of as little as 50 femtograms of explosive with very good linearity (Figure 4). At this time, the portable vapor generator (Figure 5) is offered by MicroFab as a standard commercial product. The collaboration with NIST lead to another opportunity for microdispensing in the form of a more portable test method for the field detectors. While not a the same level of accuracy, test samples created by printing explosive solution on thin substrate can be packaged and used in the filed to evaluate the operational of the detectors. The test samples still require a precise and relatively small amount of explosive making it an ideal candidate for ink-jet deposition. MicroFab designed a printing system that incorporates a very accurate micro balance. Algorithms were developed to weigh a small number of droplet (evaporation is accounted in the algorithm) to determine the drop size. The drop size is used to establish the number of drops to be deposited on the samples. In addition to NIST, MicroFab collaborated with defense groups in United States, England, The Netherlands and Australia. As part of those collaborations and in recognition of the results to date, the Trace Explosives Detection Workshop organized by NIST in the past two years has created a subgroup dedicated to the vapor generation using MicroFab’s technology. The feedback from the members of the group will be used to further improve the existing explosive vapor generator and to develop new systems. The target is to miniaturize the system to be handheld with a future goal being the incorporation in the detection systems for automatic calibration and testing. The technology created and/or improved during the project can be applied to medical diagnostic instrument, vapor based drug delivery and a variety of consumer products by adding the dimension of smell to computer interfaces. MicroFab has six patents covering these applications.
