Piezotech FC processing guide
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I - Introduction
Piezotech ® FC is a range of P(VDF-TrFE) priMVMVntable electroactive polymers. After proces飘雪直播sing, (deposition, annealing, poling etc…) they 大地成全exhibit pyroelectric and piezoelectric propertie影院视频s. Typical applications are:
● printed sensors (Pressure, temperature, Ul丁香花姑娘trasound, Infra-red),
● printed keyboards,
● printed speakers,
● printed memories,
● printed actuators
For many purposes, these polymers are used姐姐艺术 under thin film forms, obtained vi中文版飘雪a printing processes with coated electrodes.动漫影院
Piezotech® FC polymers are资源中文版 ferroelectric polymers. Figure 1 shows a typic飘雪MVal Polarization vs Applied elect中文版成全ric field plot for a film based on a Piezote在线直播ch® FC polymer. This curve exhibits a re姐姐大地mnant polarization (Pr) when no electric fie飘雪直播ld is applied. This remnant polarization can be 国语MVinverted for [E]>Ec (coercive field)GOGO.
The copolymers are characterize姑娘艺术d by their Curie Transition temperature (影院在线Tc) which corresponds to the FerMV飘雪roelectric to Paraelectric transition. This tem国语中文版perature depends on copolymer 中文版姑娘composition (see figure 2). Once poled, the pol好姑娘中文版ymers exhibit piezoelectric and pyroe好姑娘姐姐lectric properties. Typical properties for the 飘雪美丽Piezotech® FC range are given in anne中文版动漫x 1.
II - Processing
II – 1. Ink Formulation
The copolymers are soluble in different 中文版MVsolvents given in Annex 2. The concentration o姐姐动漫f the polymer in the solvent has to be adjus姑娘影院ted in order to get the approp丁香花动漫riate viscosity corresponding to the printing p影院高清版rocess used. The actual ink formulation can be ob国语高清tained by progressively adding国语视频 the polymer into the solvent under heatin艺术影院g. In order to get homogeneous film影院资源s with high electrical breakdown a filtering step艺术成全 of the solution is required (ideall动漫丁香花y 1µm or less). This will rem高清版GOove impurities and prevent the format高清版高清ion of gel particles. Standard 飘雪高清版commercial filtering processes using filtering好姑娘免费 cartridges or filtering syringe高清中文版s are commonly used.
II – 2. Processing Steps: printing 美丽好姑娘and post-treatments
The ink formulation (polymer solutio成全影院n) can be coated via different printing processesGO影院 (solvent cast, screen printing, spin-coating, 中文版姐姐ink-jet, gravure …) on a given substrate视频好姑娘 (PET, PEN, PC, glass…) under a clean atmospher高清MVe, until an homogeneous and dry 成全MVfilm is formed.In order to avoid bubbleGO国语s in the film, it is important not to use syringe动漫美丽s during the printing process.
II – 2.1. Solvent Evaporation
In order to get rid of any resi动漫直播dual solvent and enhance film properties, a so免费影院lvent evaporation step under atmospheric p飘雪艺术ressure or under vacuum can be carried out below影院免费 the solvent’s boiling-point temperat姑娘直播ure.
II – 2.2. Annealing
Annealing is a critical step to obtain the film丁香花飘雪s with the best properties. It wil飘雪资源l control crystallization of the 动漫好姑娘material and enhance electrical as w好姑娘姑娘ell as mechanical properties. For thisMV免费 purpose, films may need to be annea资源高清版led at a temperature between thGO国语e Curie temperature and the onset of crMV高清ystallization during a few minutes (typically 1美丽好姑娘5°C below the melting point). A rapiTV直播d annealing may be obtained on thin films 动漫高清using Infrared or Flash annealing.
II – 2.3. Poling
In order to activate a copolymer material中文版在线, a poling step is necessary. Using免费免费 an increasing low-frequency voltage,直播影院 an electric field above the coe影院艺术rcive field value (i.e. 50V/µm) h姐姐美丽as to be applied. Depending on the fil在线美丽m thickness, its surface, and the re高清版GOsponse precision needed, different methods can b艺术在线e used.
The application of the electric field 大地姐姐and the hysteresis curve characterization can be姐姐好姑娘 done using one of the following:
● A direct application of the electric field thr国语姑娘ough the electrodes with a volta成全视频ge generator (in this case there is no measur国语成全ement of the induced electricalMV成全 polarization (charge displacemen丁香花艺术t))
● A Sawyer-Tower circuit (electrical charges measur飘雪高清版ement, hysteresis curve)
● A ferroelectric tester (i.e.., Precision MultiFer高清版直播roelectric Radiant Technology) with an e影院GOxternal amplifier if a high electric fiel在线中文版d is needed (depending on the film thickness)
When a voltage generator is coupled 艺术丁香花with a signal generator, the electric field 影院直播can be applied according to the follow影院美丽ing parameters:
● Number of cycles to reach Emax: 15TV美丽
● Frequency: 0,05Hz (higher is possible)大地直播
● Signal: sinusoidal
● - Emax > 2Ec
● - Typically Emax=100V/µm
For printed devices (mainly thin layers飘雪成全), the poling electric field can be applied d飘雪影院irectly through the film electrodes by using a姑娘国语 direct probes contact system (figure 8). FGO飘雪or non-printed films (thick layer动漫GOs), poling can be done through cont姑娘影院acting and pressing the film between 直播高清two electrodes (figure 9). For large surfaces资源直播, a Corona poling can be used.
III - Driving & Measurements
III – 1. Deformation under an elec资源国语tric field
The deformation caused by the appli中文版艺术ed electric field can be defin姑娘资源ed by the simple formula:
Where
● represents the strain (relative defo姐姐丁香花rmation) of the sample in the xi direction
● d31 is the piezoelectric strain constan高清动漫t (in a perpendicular direction with respect to t好姑娘大地hat of the applied electric field中文版成全)
Example of an element with the followingMV成全 characteristics:
Length: l=1cm
Width: w=2mm
Thickness: t=9µm
Applied voltage: V=200V ->高清版艺术 E (electric field) = V/t
(d31, d32, d33) = (11, 10, -30) pC/N
III – 2. Sensors: Orders of Magnitude, Voltage姐姐美丽 Generation
The electric field output (E) caused by an 国语TVapplied force can be defined by:
Where:
● σi is the applied mechanical stress (N/m艺术丁香花²)
● gij is the piezoelectric voltage constant (Vm/美丽动漫Nm²)
Example of an element with the following ch直播GOaracteristics:
Length: l=2cm
Width: w=2cm
Thickness: t=100µm
(g31, g32, g33) = (216, 19, -TV影院339) *10-3 - Vm/Nm²
III – 3. Signal Measurement
The piezo sensor is stimulated wi大地高清版th a given mechanical stress and frequ姑娘国语ency (f) which generates charg艺术直播es (q). The voltage read (vt) can MV美丽likewise be proportional to the stress.姐姐免费 The limit between the proportional an国语免费d derivative modes is delimited by the cut-off fr直播中文版equency (fc). By directly connecting a senso姐姐视频r to a DAC (Data Acquisition Ca视频影院rd), Oscilloscope, the measurements are 高清版资源dependent of external impedances (sensor c免费姐姐apacity, cable losses, oscillos高清版动漫cope probe…) but their influence can be m成全国语inimized by using a charge amplifier.
Direct connection
Use of a Charge amplifier:
Annex 1: Typical properties for the Piezotech &re美丽视频g; FC & Piezotech ® RT range
Constants are given as indicaTV动漫tive value, it depends strongly on process成全姑娘ing conditions (annealing & pol丁香花视频ing) and on temperature
Annex 2: Piezotech® FC/RT solvents
Indicative list of solvents that cTV好姑娘an be used to dissolve & formulat大地姑娘e Piezotech FC® and Piezotech® RT poMV资源lymers solvent
