Fluidic self-assembly (FSA) is an exciting new method for manufacturing microscopic assemblies, including integration of electronic, mechanical, and optical devices on silicon, or of silicon electronic chips onto plastic or other substrates. The process works automatically, using random fluidic transport, allowing the placement of very large numbers of devices in minutes. Recently, industry has exploited FSA to lower dramatically the cost of radio frequency identification (RFID) tags an emerging technology for managing the flow of products, supplies and equipment automatically. The popular press has recently featured reports of WalMart, the DOD and many others urging widespread adoption of RFID technology in the supply chain.
One of the limiting factors for widescale adoption of RFID tags is their cost which is measured at dollars per tag, due to the material costs (approximately mm3 of Si) and manufacturing costs from pick and place robotic assembly. FSA can help solve both of the problems by simultaneously eliminating the robotic assembly and allowing precision assembly of much smaller tags.
The intellectual merit of this work is the consideration of the new problems that are encountered when scaling the size of the tag down. These include a host of new surface forces that can become important while volume forces, such as buoyancy and inertia become less important. Furthermore, the atomistic nature of the suspending liquid becomes apparent for the smaller size tag with the increase of Brownian motion. FSA, at large scales at least, is most efficient with a concentrated suspension of the trapezoidal tags. In order to study the dynamics of FSA within a concentrated suspension, experiments will be conducted using two classes of RFID tag substitutes, one that is transparent with a refractive index identical to that of the fluid and one that is opaque. The suspension will thus appear transparent but still display the dynamics of a concentrated suspension.
Upon the successful completion of work, the broader impacts of the work will be apparent. Cheaper ways to track consumer and defense products will lead to economic efficiencies that will benefit our society. Further, reducing shipping and storage inefficiencies will be good for the environment. The availability of ultra low-cost RFID tags is an enabler of such advances, but new information technology techniques will need to be developed to manage the vast new stores of information and drive a transformation of our national cyberinfrastructure from a network of computers to a network of computers and all tracked objects..
The novelty of the proposed experiments is that they will use suspension volume fractions in a range that is relevant to the FSA manufacturing process. Further, the exploratory nature of the work resides in finding the right combination of a solvent whose refractive index is identical to a solid material that can be microfabricated into shapes relevant to the RFID tag manufacturing process. Once these problems are tackled, a series of experiments varying solid fraction, particle size, flow rate, etc., will be performed. The dynamics of FSA at small scales will become apparent. Successful conclusion of this work will lead to a larger-scale investigation into the dynamics of the FSA with practical manufacturing parameters.
