Zoltán Rácz

Nanofabrication using nanotranslated stencil masks and lift off

We propose and demonstrate a technique for forming nanometer-scale metal features based on evaporation onto a substrate through a stencil mask. In this work, the stencil mask is laterally translated by a piezoflexure stage, between evaporations of different metals. The metals are chosen based on their etch chemistry to allow one material to be lifted off with respect to another. In this way, sidewall features are formed with dimensions and spacings controlled by moving the translational stage, which has 1 nm resolution.

Characterization and control of unconfined lateral diffusion under stencil masks.

A quantitative study of the spreading behavior of electron-beam-evaporated Al, Au, Cr, Ge, Pt, and Ti on oxidized Si substrates has been performed using translated stencil masks. At least two mechanisms are needed to account for the lateral spreading of the deposited materials: The deposition edge moves by a Fickian diffusion with a diffusion coefficient of 6.7nm2∕s at 45°C which is approximately independent of the deposited material. Once under the stencil mask, the deposited material spreads 0.1–2μm (at 45°C for under 2h), in a thin layer as a result of surface diffusion. The evaporation in N2 or O2 at 50μTorr significantly suppresses the spreading with Ti showing the greatest reduction of (7–8)×.

Dual high-frequency Surface Acoustic Wave Resonator for ultrafine particle sensing

This paper describes the development of a low-cost robust Surface Acoustic Wave Resonator (SAWR) micro sensor capable of detecting sub-micron size particles below 1 ng. The device comprises two 262 MHz Rayleigh wave SAW resonators fabricated on ST-cut quartz where one is used for particle sensing and the other as a reference channel. Electro-acoustic detection of different particles (including carbon, gold, sucrose, silicon, and PTFE) with different diameters was studied. The mass sensitivity of the SAWR was found to be typically 275 Hz/ng or 4 pg/Hz for the detection of 750 nm diameter gold particles. We believe that the device could be used as a low-cost and low power microsensor for the real-time and ubiquitous monitoring of airborne particulate matter. In particular, our SAWR sensor can be used to detect the typical levels of ultrafine particulate pollutants (PM2.5) found in city air today.

Design and Implementation of a Modular Biomimetic Infochemical Communication System

We describe here the design and implementation of a novel biomimetic infochemical communication system that employs airborne molecules alone to communicate over space and time. The system involves the design and fabrication of a microsystem capable of producing and releasing a precise mix of biosynthetic compounds and a sensor system capable of detecting and decoding the ratiometrically encoded chemical information. The research inspired by biology has been based upon the biosynthetic pathways of infochemical production and information processing within the insect world. In this novel approach, the functional equivalents of the nanoscale biological machinery are implemented by combining the latest advances and convergence of expertise in the fields of biochemistry, molecular biology, neuroscience, micro- and nanofabrication, materials science, and smart sensor and microcircuit design. The biomimetic system comprises a micromachined bio-reactor mimicking the sex gland of the female insect that releases a blend of pheromones in precisely controlled ratios, together with a cell-based biosensor system, mimicking the antennae of the male insect. The signals from the biosensors are classified and ratios decoded using a field-programmable gate array implementation of a neuromorphic model of the antenna lobe of the insect. We believe that this novel, smart infochemical communication system, inspired by the insects behavior, could eventually be implemented in VLSI technology at low cost and low power with possible application in the fields of automatic identification and data capturing, product labeling, search and rescue, environmental monitoring, and pest control

A novel biomimetic infochemical communication technology: From insects to robots

In this paper we present the development of a novel, biologically-inspired infochemical communication technology in which mixtures of infochemical ligands (in precisely controlled ratios) are used to encode multiple channels of information. Our research is inspired by infochemical production and information processing within the insect world, more specifically the moth Spodoptera littoralis. We have developed a highly innovative modular chemoemitter-receiver system, capable of information transmission using chemicals alone. The functionality of the combined infochemical communication system has been demonstrated, initially through the development of a proof-of-concept prototype based upon pre-synthesized compounds; and it will ultimately be demonstrated through a coordinated robotteam navigation task.

Cell-based surface acoustic wave resonant microsensor for biomolecular agent detection

This paper describes the development of a novel surface acoustic wave (SAW)-based biosensor system for liquid phase biomolecular agent detection. The functional layer of the biosensor comprises Sf9 insect cells that can be efficiently used for the expression of specific ligand receptors and is coupled to the acousto-electric transducer. We introduce the dual bio-SAW sensor concept where only one side of a device pair is functionalized while the other side serves as a reference: enabling a differential output that obviates common mode variations. The detection of cellular responses to octopamine (an invertebrate neurotransmitter) was used to demonstrate the biosensor systems efficacy. We believe that this biological sensor system can be used more generally to monitor changes in cell biochemistry and physiology when subjected to different biomolecular agents, e.g. the detection of receptor-specific ligand binding.

Ratiometric Chemical Blend Processing with a Neuromorphic Model of the Insect Macroglomerular Complex

We present a dynamical spiking neuromorphic model constrained by the known biology of the insect antennal lobe (AL) macroglomerular complex (MGC) implemented in a field programmable gate array (FPGA). When driven by polymer coated quartz‐crystal microbalance (QCM) chemosensors at its input, the dynamical trajectories of the model’s projection neuron (PN) output population activity encode the concentration ratios of binary odour mixtures. We demonstrate that it is possible to recover blend ratio information from the early transient phase of QCM responses that would otherwise be difficult to separate directly from chemosensor data using classical approaches. Our results demonstrate the potential of insect‐based neuromorphic signal processing methods for the rapid and efficient classification of ratiometrically encoded chemical blends.

Challenges of Biomimetic Infochemical Communication

The natural world abounds with chemical information. Animals rely on chemical communication for behaviors as diverse as finding mates, locating food sources, or avoiding predators. Insects, in particular, are capable of incredibly precise chemocommunication using low-power signaling and processing systems. Most species rely on several compounds to convey specific information, establishing a diverse palette for chemical communication. This complex form of information exchange mediated by chemicals represents an unexplored form of communication and labeling technology that has yet to be exploited. In an attempt to mimic chemocommunication in the insect world, we have developed a new class of technology based on the infochemical communication of moths. We describe how this new class of technology could be realized by combining the latest advances and convergence of expertise in the fields of pheromone biochemistry, entomology, genetics, biophysics, materials science and neuroscience. The principles of signal biosynthesis and molecular detection in olfactory receptors and the central nervous system of insects are discussed. We then describe the technological aspects of implementing a microsystem capable of producing biosynthetic compounds as well as the development of a detector unit comprising a biological cell coating expressing specific ligand receptors and coupled to an acousto-electric transducer.

Design and implementation of a modular biomimetic infochemical communication system

We describe here the design and implementation of a novel biomimetic infochemical communication system that employs airborne molecules alone to communicate over space and time. The system involves the design and fabrication of a microsystem capable of producing and releasing a precise mix of biosynthetic compounds and a sensor system capable of detecting and decoding the ratiometrically encoded chemical information. The research inspired by biology has been based upon the biosynthetic pathways of infochemical production and information processing within the insect world. In this novel approach, the functional equivalents of the nanoscale biological machinery are implemented by combining the latest advances and convergence of expertise in the fields of biochemistry, molecular biology, neuroscience, micro- and nanofabrication, materials science, and smart sensor and microcircuit design. The biomimetic system comprises a micromachined bio-reactor mimicking the sex gland of the female insect that releases a blend of pheromones in precisely controlled ratios, together with a cell-based biosensor system, mimicking the antennae of the male insect. The signals from the biosensors are classified and ratios decoded using a field-programmable gate array implementation of a neuromorphic model of the antenna lobe of the insect. We believe that this novel, smart infochemical communication system, inspired by the insects behavior, could eventually be implemented in VLSI technology at low cost and low power with possible application in the fields of automatic identification and data capturing, product labeling, search and rescue, environmental monitoring, and pest control

Low power NDIR CO 2 sensor based on CMOS IR emitter for boiler applications

In this paper we demonstrate the use of a CMOS infra-red emitter in a low power Non Dispersive Infra Red (NDIR) based carbon dioxide sensor for application in domestic boilers. Compared to conventional micro-bulbs as IR wideband sources, CMOS IR emitters offer several advantages: They are faster, smaller, have lower power consumption and can have integrated circuitry. The emitter is a 1.16 mm × 1.06 mm chip with an integrated FET drive and consists of a tungsten heater fabricated in a CMOS process followed by Deep Reactive Ion Etching (DRIE) to form a thin membrane to reduce power consumption. The NDIR sensor consists of the emitter and a commercial detector placed 5 mm apart in a simple tube. Operating the emitter at 10 Hz with a power consumption of only 40 mW, the sensor was measured in the range of 6-14% by volume of CO2, showing a resolution of 0.5%, a response time of 20 s, and low cross-sensitivity to humidity.