Passive wireless strain and pH sensing using carbon nanotube-gold nanocomposite thin films

Abstract

The recent development of wireless sensors for structural health monitoring has revealed their strong dependency on portable, limited battery supplies. Unlike current wireless sensors, passive radio frequency identification (RFID) systems based on inductive coupling can wirelessly receive power from a portable reader while transmitting collected data back. In this paper, preliminary results of a novel inductively coupled strain and corrosion sensor based upon material fabrication techniques from the nanotechnology field are presented. By varying polyelectrolyte species during a layer-by-layer fabrication process, carbon nanotube-polyelectrolyte multilayer thin film sensors sensitive to different mechanical (e.g. strain) and chemical (e.g. pH) stimuli can be produced. Validation studies conducted with different carbon nanotube thin films designed as either strain or pH sensors reveal high sensitivity and linear performance. When coupled with a copper inductive coil antenna, resulting RFID-based sensors exhibit wirelessly readable changes in resonant frequency and bandwidth. Furthermore, a carbon nanotube-gold nanocomposite thin film is fabricated and patterned into a highly conductive coil structure to realize a novel thin film inductive antenna. Preliminary results indicate that nanotube-gold nanocomposites exhibit resonance conditions, holding great promise for future RFID applications.

Tailoring Piezoresistive Sensitivity of Multilayer Carbon Nanotube Composite Strain Sensors

“…For example, SWNT-PSS/PVA thin films can be patterned as inductive coil antennas (Figure 10) for use as a conformable RFID-style sensor. For example, our current work is already exploring the inductive coupling effect between SWNT-PSS/PVA thin film coil antennas patterned on a substrate and a remote RFID reader; the resonant frequency and bandwidth of the inductive coupling effect would change with strain (Loh et al, 2007b). Using techniques such as electrical impedance spectroscopy (EIS), one can characterize the frequencydependent electrical properties of materials and their interfaces (Barsoukov and Macdonald, 2005).…”

“…However, due to the extensive cabling required for current popular strain sensors such as metal-foil strain gauges and fiber-optic Bragg gratings, dense instrumentation may not be possible. As a result, many researchers over the past decade have proposed passive wireless strain sensors, also known as radio frequency identification (RFID)-based sensors, to eliminate the need for cables and collocated power sources, thereby opening the possibility of densely instrumented embedded monitoring systems (Mita and Takahira, 2002Todd, 2005;Jia and Sun, 2006;Loh et al, 2007b). Consequently, the objective of our current research is to fabricate a miniature, cable-free, thin film, passive wireless strain sensor capable of being embedded within structural materials (e.g., reinforced concrete, among others).…”

Sensitivity Modeling of an RFID-Based Strain-Sensing Antenna With Dielectric Constant Change

“…Other researchers have proposed passive wireless strain sensing through analog mechanisms to reduce the complexity of the wireless nodes [10][11][12][13][14]. This passive approach removes the process of onboard digitization, eliminates the requirement for a microcontroller in the sensor node, and usually entails an electromagnetic antenna with known resonance frequency.…”

Fiber Optic pH Sensor Using Optimized Layer-by-Layer Coating Approach

“…glass, ceramics, metals, wood and plastics [5][6][7], taking also into account their varying size and topology [8,9]. In essence, the process of deposition is based on electrostatic attraction and can be used with various reagents such as polymers, nanoparticles, metals, dyes, quantum dots and nanotubes [10][11][12][13][14][15] , biomolecules such as enzymes [16] and proteins [17], etc. In this technique, a charged substrate is alternatively immersed into polyanion and polycation solutions to build up a multilayer coating.…”