UM File # 3687

Background
Around the world, civil infrastructures such as buildings, bridges, lifelines, among others, represent the foundation for economic welfare and societal prosperity. Many of these vital structures are beginning to approach (or have already exceeded) their design service lifetimes. Today, $91 billion is spent annually to maintain the U.S. inventory of highways and bridges; however, an additional $128 billion is needed to upgrade existing structures to current standards. As such, efficient and cost-effective strategies are required to ensure infrastructure serviceability and safety. In most cases, the current state of practice relies on schedule-based maintenance routines in which engineers rely on visual inspection to assess structural performance. Not only is this method subjective, but a schedule-based maintenance program is often economically inefficient, as newer structures may not need inspection during their initial years of service.

Technology Description
Researchers at University of Michigan have developed a unique multifunctional material in which strain and corrosion transduction mechanisms can be encoded using nanotechnology. 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. When coupled with a copper inductive coil antenna, resulting RFID-based sensors exhibit wirelessly readable changes in resonant frequency and bandwidth.

Applications
• Radio frequency identification systems (RFID)

Advantages
• Low wireless sensor costs
• Small form factor
• High degree of sensitivity to strain and corrosion in structures

File Number: 3687