1. Activity: A Pyroelectric Smart Sensor
PVDF-A polymer with many uses

2. What is a Smart Sensor?
We will use the term “Smart Sensor” to refer to systems that employs a sensor device mated to microelectronics. In this activity we will use metal coated PVDF films as our sensor system and a computer will take the place of the microelectronics. The system used in this activity is not engineered to minimize size and power consumption but clearly those would be goals in any widely deployed commercial device.

3. Preparation for Activity
Items Needed: PVDF sensor films; electronic components for circuits A and C (to be described) ; computer with data acquisition hardware/software.
Am understanding of Piezoelectric Effect
An understanding of Pyroelectric Effect
An understanding of the role of molecular structure in determining the piezoelectric properties of PVDF 

4. Discussion Points Why is the b form of PVDF piezoelectric?
How is the b form of PVDF Produced?
What is the relationship between piezoelectric effect and the pyroelectric effect?
What does the infrared spectrum of PVDF tell us about the wavelengths where the pyroelectric properties of PVDF might be most easily observed?

5. Representations of the molecular structure of the vinylidene difluoride (VD) monomer and of the a and b forms of the PVDF polymer.
                
VD-wire
PVDF-a form
PVDF-b form
VD-space filling

6. Infrared Spectrum of PVDF taken on a Bruker IFS 66v spectrometer,
equipped with a DTGS detector and a KBr beamsplitter.
Note that the strong absorption around 1000 cm-1

7. Discussion Points II
How can we detect the piezoelectric or pyroelectric effect exhibited by a PVDF film?
What is needed in terms of electronic and computer components to produce a smart sensor?

8. Commercially available metal coated piezoelectric PVDF sensor elements
A Film
in (mm)
B Electrode
C Film
D Electrode
t (µm)
Cap (nF)
.520 (13)
.400 (10)
.980 (25)
.580 (14.70)
205
.500
.640 (16)
.484 (12)
1.63 (41)
1.19 (30.17)
1.38

9. Electronic Circuits PVDF generates a measureable voltage
Circuits with a very high Input impedance required
Low power consumption, battery operated systems desirable for portability.
(A) Impedance Adaptor,
Voltage Follower
(C) Differential Amplifier, for measuring relative/combined signals
(B) Electric Charge Measurement

10. Four Panel Thermal Detection-Individual panels are connected to a dedicated circuit (A).

11. USB data port interfaced to laptop computer gives system properties of a “smart sensor”.

12. Voltage output 4 panel Pyroelectric Sensor when exposed to an asymmetrically located heat source

13. Discussion Points
Design a pyroelectic smart sensor system capable of to locating a single person in a room.
Design a system which would make a PVDF pyroelectric sensor sensitive to a wide range of wavelengths.
What information might be obtained from the voltage rise and decay exhibited on the thermal response curves
What can be done to stabilize a PVDF pyroelectric sensor system?