Applications | Practical Applications for Piezo PVDF

Self Shielding Dynamic Strain Gages

High fidelity dynamic strain gages (i.e. contact microphones) are conveniently shielded by affixing together two Piezo Film elements with the ground electrodes on the outer, exposed surfaces. This simple technique provides excellent EMI protection, and doubles the sensitivity of the transducer.

Optically Transparent Sensing

Piezo Film is optically clear. ITO or PEDOT are transparent conductors that can be applied to Piezo Film to produce optically transparent sensors. Glass break detectors, touch activated sensors on LCD or LED displays, and keyless entry on windows are examples.

Wake Up Switch

Piezo Film generates sufficient voltage to wake up a high input impedance CMOS circuit (ie JFET). Sensor applications that remain essentially dormant for months or years, like fire alarm or intrusion detection, or applications constrained by ultra-low power can benefit by the circuit wake up capability of Piezo Film.

Common Mode Rejection

Two identical electrode patterns applied to a single Piezo Film element respond equally to strain, vibration, noise or thermal changes, and can be connected to cancel an input common to both sensing patterns. Meanwhile, any mechanical strain or thermal signal applied to one electrode but not seen by the other is sensed. Interdigitated (saw tooth) electrode patterns can sense the velocity of a finger swiping across the interdigitated fingers, while cancelling common strain or thermal inputs.

Flexible Piezo Cable

Piezo film can be cut into long, narrow strips and wrapped around or taped parallel to the length of cylindrical surfaces like fiber, cable, hose, pipe, and shafts as continuous contact microphones detecting flow, leak, impact, vibration and fault conditions. Continuous sensing of up to kilometer lengths with a single Piezo Film strip is both inexpensive and minimizes interconnect cost and reliability.

Ultrasonic Transducers

Thin film piezoelectric copolymer is an exceptional ultrasonic transmitter and receiver, particularly at very high frequencies (5 or 10kHz and above). Applications include high resolution imaging of surfaces such as transdermal scanning, intravenous catheter imaging, and non-destructive testing.

Naturally Buoyant

Piezo Film is very light weight, and can be formed into hydrophones having high sensitivity, but is naturally buoyant. This eliminates the need for oil filling of seismic cable in geophysical applications.

Pyroelectric Sensors

Piezo Film and Copolymer are very sensitive to temperature change. The heat form the body, such as an exhale, will produce a signal of about 10 Volts for each respiration cycle. A finger print reader has been developed which senses the temperature differential between the ridges of the finger print.

Acoustic Impedance

The low acoustic impedance of Piezo Film allows for low transmission loss of acoustic signals into Piezo Film. Vital signs monitoring of heart beat, blood and air flow, lung sounds, and voice are easily accomplished with small Piezo Film elements affixed to the skin with medical grade adhesives.

Practical Applications of Piezo Film

There is a very long list of practical applications for Piezo Film. The following is a sampling to demonstrate the breadth of sensor solutions made possible by this unique material.

Consumer & Appliances

  • High fidelity acoustic pickups for musical instruments
  • Impact switches and sensors – sporting equipment
  • Audio speakers and microphones
  • Low cost touch switches and swipe sensors in toys, games, appliances, electronic devices
  • Finger print authentication
  • Pen digitizer for white board;  signature verification
  • Wearable electronics – smart fabric, pedometer, micro-energy harvesting
  • Printed electronics

Acoustic Pickups

Speaker & Microphone

Pen Digitizer

Printed Electronics

Security

  • Area intrusion detection under door mats, carpets, or flooring
  • Glass break detection
  • Infrared Motion sensors
  • Piezo Cable for perimeter monitoring (buried or fence mounted)
  • Wake up switch on doors, windows
  • Asset tracking (shock, vibration, tamper)

Medical

  • Vital signs monitoring – heart rate, respiration, motion artifacts, flow, lung sounds, apnea, snoring, REM, TMJ
  • Biosensors – tactile, gait, orthopedics, handicapped assist
  • Smart home for eldercare, Smart Bed/Chair,  Smart Floor
  • Ultrasonic Imaging
  • Electronic stethoscope
  • Voice amplification

Energy & Utilities

  • Seismic sensors - hydrophones, geophones
  • Pipeline leak detection
  • Fault detection – wind turbines
  • Energy harvesting – micropower
  • Water metering

Industrial & Instrumentation

  • Machine monitoring dynamic strain sensors
  • Switches
  • Robotic tactile sensing
  • Vending
  • Flow meter, rupture sensor
  • Nondestructive testing, acoustic emission
  • Infrastructure monitoring
  • In road traffic sensors (truck weight in motion, vehicle speed and red light enforcement)