Introduction of the revolutionary drop-on-demand (DoD) inkjet printing technique for microelectronics allows the use of flexible substrate, organic and inorganic materials, and low-cost volume fabrication. However, inks of different functional materials for varieties of applications are still under development. Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), a potential candidate for mechanical and acoustic sensors, actuators, energy harvesting and nonvolatile memory applications, is a copolymer that exhibits piezo-, pyro-and ferro-electric properties. During this work, inkjetprinted films using high molecular weight PVDF-TrFE were developed and characterized to investigate their morphology and crystallinity. Modified waveform and very low jetting frequency have been used to accommodate relaxation time of the polymeric ink during jetting. Crystallographic studies confirm the presence of a β-phase, which exhibits spontaneous polarization per unit cell.

International audienceNanostructured silicon-based materials are good candidates for thermoelectric (TE) devices due to their low thermal conductivity, customizable electrical conductivity, and reduced cost. Generally, nanostructured TE bulk materials are obtained through compaction and sintering at high temperature (>1000 °C) of silicon nanoparticles (NPs). In order to introduce TE generators in flexible electronic devices, development of thin film TE is needed. Inkjet-printing of silicon NPs-based ink is an interesting technology for this targeted application due to its low cost and additive process. This paper presents the implementation of inkjet-printing of a silicon NPs-based ink toward the fabrication of TE material on flexible substrate and the development of a characterization method for this material. After printing, recovering of electrical properties through sintering is mandatory. Nevertheless, special care must be taken in order to keep thermal conductivity low and reduce the annealing temperature to allow the use of flexible substrates. The functional properties: electrical and thermal (measured by Raman spectroscopy), are studied as a function of the annealing process. Two types of annealing: rapid thermal annealing and microwave annealing, are investigated as well as two atmospheres: inert (N2) and reducing (N2-H2 5%)

A capacitive acoustic resonator developed by combining three-dimensional (3D) printing and two-dimensional (2D) printed electronics technique is described. During this work, a patterned bottom structure with rigid backplate and cavity is fabricated directly by a 3D printing method, and then a direct write inkjet printing technique has been employed to print a silver conductive layer. A novel approach has been used to fabricate a diaphragm for the acoustic sensor as well, where the conductive layer is inkjet-printed on a pre-stressed thin organic film. After assembly, the resulting structure contains an electrically conductive diaphragm positioned at a distance from a fixed bottom electrode separated by a spacer. Measurements confirm that the transducer acts as capacitor. The deflection of the diaphragm in response to the incident acoustic single was observed by a laser Doppler vibrometer and the corresponding change of capacitance has been calculated, which is then compared with the numerical result. Observation confirms that the device performs as a resonator and provides adequate sensitivity and selectivity at its resonance frequency.

This paper describes the fabrication process and the method to determine the membrane tension and defects of an inkjet-printed circular diaphragm. The membrane tension is an important parameter to design and fabricate an acoustic sensor and resonator with the highest sensitivity and selectivity over a determined range of frequency. During this work, the diaphragms are fabricated by inkjet printing of conductive silver ink on pre-strained Mylar thin films, and the membrane tension is determined using the resonant frequency obtained from its measured surface velocity response to an acoustic excitation. The membrane is excited by an acoustic pressure generated by a loudspeaker, and its displacement (response) is acquired using a laser Doppler vibrometer (LDV). The response of the fabricated membrane demonstrates good correlation with the numerical result. However, the inkjet-printed membrane exhibits undesired peaks, which appeared to be due to defects at their boundaries as observed from the scanning mode of LDV.