Highly piezoelectric, thermal stable ferroelectrets from cyclic olefin copolymer. Yan Li, Hui Wang, Changchun Zeng ANTEC 2015, Orlando

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1 Highly piezoelectric, thermal stable ferroelectrets from cyclic olefin copolymer Yan Li, Hui Wang, Changchun Zeng ANTEC 2015, Orlando

2 Content 1. Introduction 2. COC ferroelectret 3. Hybrid COC-PDMS ferroelectret

3 Problem Statement: 1. Introduction Need for a lightweight, low cost, high sensitivity and human-friendly wearable piezoelectric material based equipment Large demand of sensors made with non-toxic materials Lack of movement flexibility of traditional piezoelectric materials > Present market for printed and flexible sensors is $140 million > Market in 2023 will be over $1 billion

Comparison of piezoelectric coefficients of several piezoelectric materials Piezoelectric material Crystal: Quartz (silicon dioxide) Ceramic: Lead zirconate titanate (PZT) Ferroelectrics: β-phase

4 Comparison of piezoelectric coefficients of several piezoelectric materials Piezoelectric material Crystal: Quartz (silicon dioxide) Ceramic: Lead zirconate titanate (PZT) Ferroelectrics: β-phase polyvinylidene (β-pvdf ) Ferroelectret: optimized cellular polypropylene (PP) d 33 (pc/n) 2 (d 11 ) PZT does not has the polymer advantages (softness and light-weight) PVDF low piezoelectric activity PP low applied temperature (-20 o C ~ 50 o C) limits their usefulness

opposite sign on the upper and lower walls form macroscopic dipoles.

5 Ferroelectrets Ferroelectrets, are space-charged porous polymers with significant piezoelectricity d Q F V The cellular voids with charges of opposite sign on the upper and lower walls form macroscopic dipoles. The effective dipole moment changes under mechanical stress and gives rise the piezoelectricity

of the sensor Low cost, very low cost compare to traditional piezoelectric materials Lightweight, high energy

6 Benefits of Ferroelectrets High sensitivity, high enough to be embedded into pressure management devices Non-toxic, crucial when materials be used with human direct contact Flexible, enables large movement detection of the sensor Low cost, very low cost compare to traditional piezoelectric materials Lightweight, high energy harvesting efficiency A curved sensor array made by piezoelectric foam Piezoelectric foams sensor attached to human body

7 Problem in current commercial ferroelectrets Cellular polypropylene (PP) film High piezoelectric coefficient of ~ 1000 pcn -1, but very low operation temperature (<60 o C), due to the poor charge storage stability of PP. Develop new thermally stable polymer ferroelectrets. polytetrafluoroethylene fluorinated ethylene propylene polyethylene terephthalate (PET) polyethylene naphthalate (PEN ) polycarbonate (PC) polyetherimide (PEI) cyclo-olefin copolymers (COCs)

8 Cyclo-olefin Copolymer (COC) a x y COC meets all these requirements: I. Low water absorption, < 0.01% II. High electrical resistivity, >10 13 Ω cm COC is superior to any known positively charged polymer (PET, PEN, FEP, PTFE, PETP, etc.)

9 Low piezoelectric activity However, d 33 of COC ferroelectrets are reported typically in the range: pc/n.

10 OUR GOAL Develop Thermally Resistant, High Sensitive Polymer Based Piezoelectric Materials based on: 1. Introduction >Promising candidate materials 2. COC ferroelectret Cyclic Olefin Copolymers (COCs) Highly Thermally Stable, Excellent Charge Capacity, Thin, Lightweight, Water Resistant, and Flexible 3. Hybrid COC-PDMS ferroelectret >Novel fabrication technology

11 1. Introduction 2. COC ferroelectret 3. Hybrid COC-PDMS ferroelectret

12 2. COC ferroelectrets of high piezoelectricity Structure Design 1 d33 K E eff Li, Y., Zeng, C. Macromolecular Chemistry and Physics 2013, 214, The basic mechanism in the novel COC ferroelectrets is simple: allow the multilayer structure to bending.

13 Schematic of the fabrication process b Laser cutting machine 1 Laser 2 metallised COC film patterned COC film central COC film patterned COC film metallised COC film 4 Charging 3 CO 2 bonding F, co 2 Charging equipment Very low bonding temperature (120 o C) A multi-layer COC films with a multipoint short-beam structure by combining laser cutting and carbon dioxide bonding techniques. High pressure vessel

b Deformation ( m) 0-2 -4-6 -8 w = 1 mm w =1.5 mm w = 2 mm w = 2.

14 b Deformation ( m) w = 1 mm w =1.5 mm w = 2 mm w = 2.5 mm -10 w = 3 mm Position (mm) Finite element modeling results of the overall deformation in the thickness direction of the COC ferroelectrets with different geometry.

15 Deformation ( m) c mm 2 mm 3 mm P (kpa) Simulated deformation (in thickness direction) of COC ferroelectrets with different design under a series of pressure showing excellent linear response.

16 c T g (K) CO 2 Pressure (MPa)

Piezoelectric Activity a d 33 (pc/n) 10 4 10 3 10 2 10 1 2.

5 mm 15 pc/n 10 0 0 5 10 15 20 Applied pressure (kpa) The

17 Piezoelectric Activity a d 33 (pc/n) mm 3 mm 2 mm 3 mm (no overlap) 1.5 mm 15 pc/n Applied pressure (kpa) The control of geometry structure allow a direct adjustment of piezoelectric activity

18 Thermal Stability b 1.0 Normalized d Short-term test Temperature ( o C) The piezoelectric d 33 coefficients of samples only exhibited a slight decay after a thermal treatment at o C.

19 c 1.0 Normalized d Long-term test Time of thermal treatment (h) The retained d 33 coefficient only drops to 70 % of the initial value annealing at 110 o C for 200 h.

20 Current (pa) Thermal Stimulated Discharge Temperature ( o C)

21 Polarization (uc/cm2) Hysteresis loop Polarization (500V) Polarization (1000V) Polarization (1500V) Polarization (2000V) Polarization (2500V) Polarization (3000V) Polarization (4000V) Polarization (5000V) Polarization (6000V) Polarization (7500V) Voltage (volt)

22 Quasi-permanent Polarization (uc/cm2) Piezoelectric Coefficient (pc/n) Quasi-permanent Polarization (at 4.9kPa) Piezoelectric Coefficient (at 4.9kPa) Applied voltage (kv)

23 Displacement (micron) Actuation behavior Drive Voltage (volt)

24 Current (pa) Quasi-permanent Polarization (uc/cm2) Piezoelectric Coefficient (pc/n) Effect of different types of COC Applied Voltage (volt) Applied Pressure (kpa) Temperature ( o C)

25 Piezoelectric Coefficient (pc/n) Structure Design 2 Eye-shape structure Applied Pressure (kpa)

26 1. Introduction 2. COC ferroelectret 3. Hybrid COC-PDMS ferroelectret

27 3. Hybrid ferroelectrets: sandwich structure with rubber layers

29 Electric output of a typical COC-PDMS ferroelectret

Compression force (N) Photograph of the test set-up 50 40 30 20 10 0 0 10 20 30 40 50

30 Compression force (N) Photograph of the test set-up Time (s) Compression force under cycling compression at a given compression rate 20 mm/min

31 Open-Circuit Voltage (V) Short-Circuit Current (na) Time (s) Time (s) Measured open- circuit voltage and short- circuit current under cycling compression

Voltage (V) Images of a commercial red LED in dim background before and the moment of being lit up by the storage energy. Circles 0 100 200 300 400 500 0.6 0.5 0.4 0.3 0.2 0.1 0.

32 Voltage (V) Images of a commercial red LED in dim background before and the moment of being lit up by the storage energy. Circles Time (s) The charging curve across a single capacitor when pumped by a under cycling compression test, showing a steady increase in the storage charge charges with the increase of charging time.

33 Thank you! High-Performance Materials Institute Florida State university

PIEZOELECTRIC FOAMS BASED ON CYCLIC OLEFIN COPOLYMER

PIEZOELECTRIC FOAMS BASED ON CYCLIC OLEFIN COPOLYMER Hui Wang, Yan Li, and Changchun Zeng* High-Performance Materials Institute Department of Industrial and Manufacturing FAMU-FSU College of Engineering