The medium-term goal of this project is to develop a Bio-enabled Sensor Network (BSN) composed of sensing devices that can enter a full sleep mode but still be woken up by a long-range RF signal. The idea is to transduce a weak Electro-Magnetic signal into biological signals and use a biological device to demodulate the information embedded in the EM signal. The short-term goal of this project is to develop a clear vision for the potential of biological communications and computation in the specific context of wireless sensor networks (WSN) and articulate a research path and preliminary answers to the following questions. What are the fundamental limits of EM energy harvesting? In the specific case of address recognition in WSN, what are the potential, means and limits of computation, communication, of a distributed network of biological processes? Beyond, the intra-node networked bio-communications and computation, the wake-up mechanism results in optimization problems because of its high delay and limited capacity. How can hybrid, biological and periodic, wake up mechanisms be combined to satisfy the system requirements? What is the viability of using biological organisms in WSNs?
Research in biological and molecular communications and computation holds the promise to revolutionize and bridge the fields of computer science, biology, electrical engineering, and mechanical engineering. The PI aims at obtaining preliminary results, and assembling a cross-disciplinary team with expertise in computation, communication, networking, biology, and nano-mechanics, to write a full proposal with clear, focused, and realistic objectives to develop a prototype BSN.
One of the major challenges in conserving energy in wireless sensor networks is to reduce the energy consumption of the RF receiver. Todayâ€™s techniques rely on periodically waking up the receiver to synchronize and respond to the requests of a master node. Ideally, a sensor node should go in a full-sleep mode that consumes zero energy and only wake up on external requests or events. In this projects we are interested in exploring new mechanisms for energy efficient radio-frequency receivers. We contend that the energy efficiency of biological systems can be harnessed to design and build a combined RF-biological nano-power sensing device, bringing us closer to the ideal wireless sensor node. In order to reach the long-term goal of integrating and enabling wireless and biological systems, we surveyed several RF-to-Biological communication mechanisms and architectures. We specifically investigated RF to chemical gradient transduction, RF energy harvesting, energy transfer in electrically and magnetically coupled mechanical nano-resonators, and RF to torque transducers in biological settings. RF-Energy to Chemical-Gradient: We proposed an architecture for a wireless sensor node to remain in a full sleep mode while being responsive to remote queries sent over the RF signal. This can be achieved using an extremely low power wake-up system to trigger a Low Power Sensor Node (LPSN). The received RF signal from the antenna is extremely weak, thus cannot be used directly to wake up the LPSN. We proposed to combine the RF energy harvesting mechanism with the energy efficiency of biological processes. The system accumulate the energy of the RF signal and transduces it into a biological signal. The incoming signal information is processed using the energy-efficient biological system and if necessary triggers the wake up of the LPSN. The proposed system has three components: (1) a passive RF Front End (RF-FE) to harvest and detect the weak remote RF signal, (2) a Bio-Mechanical Signal Interpreter (BMSI) to efficiently execute the signal demodulation and generate the wake-up signal, and (3) a Low Power Sensor Node (LPSN). We analyzed the performance of the proposed mechanisms and components. We obtained preliminary analytical results for the performance of our RF-FE prototype, outlined the design alternatives for the BMSI, and obtained theoretical results for characterizing the BMSI components performance. RF-Energy Harvesting: We developed and built a prototype for the RF-FE energy harvester and demonstrated promising performance. The RF-FE, a WiFi tailored, modified Greinacher voltage multiplier, a highly efficient parallel full-wave rectifier, is designed, prototyped and fully characterized. It features an energy-harvesting efficiency of upto 82% and collecting upto 2.5mW from a phone WiFi transmission. Energy Transfer in Electrically and Magnetically Coupled Mechanical Nano-Resonators: Using the resonant scattering theory, we have shown that magnetically coupled resonators can achieve the same energy transfer performance as for their electrically coupled counterparts, or even outperform them within the scale of interest. Torque Transduction in Biological Settings: We designed a nano-scale radio-receiver that is capable of achieving resonance in biological settings. The system is based on a magnetic nanoparticle attached to a carbon nanotube cantilever. The receiver transduces the magnetic field into a radio-frequency torque. The benefit of using magnetic fields is that, unlike electric fields, they couple weakly with non-targeted biological tissues. This makes tunable resonance at fairly high frequencies feasible in biological settings, therefore enabling several unique capabilities such as multiplexed interaction and targeted actuation. We conduct theoretical analysis for the system and predict the desired functionality within reasonable scale for frequency (few MHz - few GHz), carbon nanotube size (100s nm), and magnetic nanoparticles size (100s nm). We believe this will open several new avenues for research in the areas of targeted actuation of mechano-sensitive and thermo-sensitive ion channels, the modulation of cell functions, and controlled drug delivery.