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Fagas G.,Tyndall National Institute | Nolan M.,Tyndall National Institute | Georgiev Y.M.,Tyndall National Institute | Yu R.,Tyndall National Institute | And 21 more authors.
Microsystem Technologies | Year: 2014

We present the design considerations of an autonomous wireless sensor and discuss the fabrication and testing of the various components including the energy harvester, the active sensing devices and the power management and sensor interface circuits. A common materials platform, namely, nanowires, enables us to fabricate state-of-the-art components at reduced volume and show chemical sensing within the available energy budget. We demonstrate a photovoltaic mini-module made of silicon nanowire solar cells, each of 0.5 mm2 area, which delivers a power of 260 μW and an open circuit voltage of 2 V at one sun illumination. Using nanowire platforms two sensing applications are presented. Combining functionalised suspended Si nanowires with a novel microfluidic fluid delivery system, fully integrated microfluidic-sensor devices are examined as sensors for streptavidin and pH, whereas, using a microchip modified with Pd nanowires provides a power efficient and fast early hydrogen gas detection method. Finally, an ultra-low power, efficient solar energy harvesting and sensing microsystem augmented with a 6 mAh rechargeable battery allows for less than 20 μW power consumption and 425 h sensor operation even without energy harvesting. © 2014 Springer-Verlag Berlin Heidelberg.

Xu J.,IMEC | Offermans P.,IMEC | Meynants G.,CMOSIS nv | Duy Tong H.,Nanosens BV | And 2 more authors.
Microelectronics Journal | Year: 2010

This paper presents a fully integrated lock-in amplifier intended for nanowire gas sensing. The nanowire will change its conductivity according to the concentration of an absorbing gas. To ensure an accurate nanowire impedance measurement, a lock-in technique is implemented to attenuate the low frequency noise and offset by synchronous demodulation or phase-sensitive detection (PSD). The dual-channel lock-in amplifier also provides both resistive and capacitive information of the nanowire in separate channels. Measurement results of test resistors and capacitors show a 2% resolution in the resistance range 1040 kΩ and a 3% resolution in the capacitance range 0.51.8 nF. Moreover, a 28.732.1 kΩ impedance variation was measured through the lock-in amplifier for a single palladium nanowire that was exposed to a decreasing hydrogen concentration (10% H2 in N2 to air). The chip has been implemented with UMC 0.18 μm CMOS technology and occupies an area of 2 mm2. The power consumption of the readout circuit is 2 mW from a 1.8 V supply. © 2010 Elsevier Ltd. All rights reserved.

Srivastava S.K.,Wageningen University | Srivastava S.K.,Laboratory of Organic Chemistry | Ramaneti R.,Nanosens B.V. | Roelse M.,Wageningen University | And 7 more authors.
RSC Advances | Year: 2015

Impedance spectroscopy of cell lines on interdigitated electrodes (IDEs) is an established method of monitoring receptor-specific cell shape changes in response to certain analytes. Normally, assays are done in multiwells making it a bulky, static and single use procedure. Here, we present a biosensor allowing sequential application of biological test samples with an automated microfluidic system. It is capable of monitoring relative changes in impedance using castellated IDEs of 250-500 μm diameter, covered with stable or reverse transfected HEK293 cells. Reversible activation of the Neurokinin 1 (NK1) receptor in stable cell lines was observed in response to a series of 5 minute exposures from 1 pM-10 nM of the specific ligand Substance P (SP) using impedance measurements at 10 mV and 15 kHz. An optimal flow speed of 10 μl min-1 was chosen for the 10 μl flow cell. The EC50 of ∼10 pM was about 10 times lower than the EC50 based on measuring changes in the calcium ion concentration. The method was also shown to work with reverse transfected cells. Plasmid DNA encoding the NK1 gene was spotted onto the electrodes and pre-incubated with a transfection agent. The overlaid HEK293 cells were subsequently transfected by the underlying DNA. After challenge with SP, the cells induced an activation response similar to the stable cell line. The microfluidic micro-electrode reverse transfection system opens up possibilities to perform parallel measurements on IDE arrays with distinct receptors per IDE in a single flow channel. This journal is © The Royal Society of Chemistry.

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