Flexible Lead-Free Piezoelectric Composite Materials for Energy Harvesting Applications

Vibrational piezoelectric energy harvesters are being investigated to replace batteries in embedded sensor systems. The energy density that can be harvested depends on the figure of merit, d₃₃g₃₃, where d₃₃ and g₃₃ are the piezoelectric charge and voltage coefficient. Commonly used piezoelectric...

Depolarization of multidomain ferroelectric materials

Depolarization in ferroelectric materials has been studied since the 1970s, albeit quasi-statically. The dynamics are described by the empirical Merz law, which gives the polarization switching time as a function of electric field, normalized to the so-called activation field. The Merz law has been used for decades; its origin as domain-wall...

Collective electrical oscillations of a diatom population induced by dark stress

Diatoms are photosynthetic microalgae, a group with a major environmental role on the planet due to the biogeochemical cycling of silica and global fixation of carbon. However, they can evolve into harmful blooms through a resourceful communication mechanism, not yet fully understood. Here, we demonstrate that a population of diatoms under...

Integrated circuits based on conjugated polymer monolayer

It is still a great challenge to fabricate conjugated polymer monolayer field-effect transistors (PoM-FETs) due to intricate crystallization and film formation of conjugated polymers. Here we demonstrate PoM-FETs based on a single monolayer of a conjugated polymer. The resulting PoM-FETs are highly reproducible and exhibit charge carrier...

Spatially resolved solid-state reduction of graphene oxide thin films

Re-establishment of electrical conductivity in graphene oxide (GO), the insulating form of graphene, is (partially) accomplished by reduction through high temperature treatments in a reducing atmosphere, or using strongly reducing chemicals or electrolytic processes. The reduction methods are suited for bulk graphene oxide. Spatially resolved...

Interfacial conduction in organic ferroelectric memory diodes

Solution-processed memory diodes based on phase separated blends of ferroelectric and semiconducting polymers in the low resistance on-state operate similar to a vertical field-effect transistor at the pinch-off. Numerical simulations have shown that the performance of the diode is dominated by the conduction of charge carriers at the...

Analysis and experimental validation of the figure of merit for piezoelectric energy harvesters

Piezoelectric energy harvesters are at the front of scientific research as enablers of renewable, sustainable energy for autonomous wireless sensor networks. Crucial for this disruptive technology is the achievable output power. Here we show, analytically, that the maximum output energy per unit volume, under a single sinusoidal excitation,...

Dynamics of direct X-ray detection processes in high-Z Bi₂O₃ nanoparticles-loaded PFO polymer-based diodes

Semiconducting polymer based X-ray detectors doped with high-Z nanoparticles hold the promise to combine mechanical flexibility and large-area processing with a high X-ray stopping power and sensitivity. Currently, a lack of understanding of how nanoparticle doping impacts the detector dynamics impedes the optimization of such detectors. Here...

Ferroelectricity and piezoelectricity in soft biological tissue: Porcine aortic walls revisited

Recently reported piezoresponse force microscopy (PFM) measurements have proposed that porcine aortic walls are ferroelectric. This finding may have great implications for understanding biophysical properties of cardiovascular diseases such as arteriosclerosis. However, the complex anatomical structure of the aortic wall with different...

Quantum tunnelling and charge accumulation in organic ferroelectric memory diodes

Non-volatile memories—providing the information storage functionality—are crucial circuit components. Solution-processed organic ferroelectric memory diodes are the non-volatile memory candidate for flexible electronics, as witnessed by the industrial demonstration of a 1 kbit reconfigurable memory fabricated on a plastic foil. Further progress,...

Flexible Piezoelectric Touch Sensor by Alignment of Lead-Free Alkaline Niobate Microcubes in PDMS

A highly sensitive, lead-free, and flexible piezoelectric touch sensor is reported based on composite films of alkaline niobate K_0.485Na_0.485Li_0.03NbO₃ (KNLN) powders aligned in a polydimethylsiloxane (PDMS) matrix. KNLN powder is fabricated by solid-state sintering and consists of microcubes. The...

Extracellular electrical recording of pH-triggered bursts in C6 glioma cell populations

Glioma patients often suffer from epileptic seizures because of the tumor’s impact on the brain physiology. Using the rat glioma cell line C6 as a model system, we performed long-term live recordings of the electrical activity of glioma populations in an ultrasensitive detection method. The transducer exploits large-area electrodes that maximize...

Thin film thermistor with positive temperature coefficient of resistance based on phase separated blends of ferroelectric and semiconducting polymers

We demonstrate that ferroelectric memory diodes can be utilized as switching type positive temperature coefficient (PTC) thermistors. The diode consists of a phase separated blend of a ferroelectric and a semiconducting polymer stacked between two electrodes. The current through the semiconducting polymer depends on the ferroelectric...

Retention of intermediate polarization states in ferroelectric materials enabling memories for multi-bit data storage

A homogeneous ferroelectric single crystal exhibits only two remanent polarization states that are stable over time, whereas intermediate, or unsaturated, polarization states are thermodynamically instable. Commonly used ferroelectric materials however, are inhomogeneous polycrystalline thin films or ceramics. To investigate the stability of...

Scaling behavior and parasitic series resistance in disordered organic field-effect transistors

The scaling behavior of the transfer characteristics of solution-processed disordered organic thin-film transistors with channel length is investigated. This is done for a variety of organic semiconductors in combination with gold injecting electrodes. From the channel-length dependence of the transistor resistance in the conducting ON-state, we...

Switch-on voltage in disordered organic field-effect transistors

The switch-on voltage for disordered organic field-effect transistors is defined as the flatband voltage, and is used as a characterization parameter. The transfer characteristics of the solution processed organic semiconductors pentacene, poly(2,5-thienylene vinylene) and poly(3-hexyl thiophene) are modeled as a function of temperature and gate...