Research into energy harvesting from ambient vibration sources has attracted great interest over the last few years, largely as a result of advances in the areas of wireless technology and low-power electronics. One of the mechanisms for converting mechanical vibration to electrical energy is the use of piezoelectric materials, typically operating as a cantilever in a bending mode, which generate a voltage across the electrodes when they are stressed. Typically, the piezoelectric materials are deposited on a non-electro-active substrate and are physically clamped at one end to a rigid base. The presence of the substrate does not contribute directly to the electrical output, but merely serves as a mechanical supporting platform, which can pose difficulties for integration with other microelectronic devices. The aim of this paper is to describe a novel thick-film free-standing cantilever structure that does not use a supporting platform and has the advantage of minimizing the movement constraints on the piezoelectric material, thereby maximizing the electrical output power. Two configurations of the composite cantilever structure were investigated: unimorph and multimorph. A unimorph consists of a pair of silver/palladium (Ag/Pd) electrodes sandwiching a laminar layer of lead zirconate titanate (PZT). A mulitmorph is an extended version of the unimorph with two pairs of Ag/Pd electrodes and three laminar sections of PZT.

Abstract-In this paper, free-standing structures in the form of cantilevers, fabricated by using a combination of conventional thick-film technology and sacrificial layer techniques, is proposed. These structures were designed to operate as energy harvesters at low-levels of ambient vibration and were characterised using a shaker table over a range of frequencies and acceleration levels. A cantilever with dimensions of 13.5 mm long by 9 mm wide and total thickness of 192 µ µ µ µm was found to have Young's modulus of 3. Ω. The addition of a proof mass was shown to improve the electrical output power generation. In a series of experiments, the electric power generated by a beam having a proof mass of 2.2 g, resulted in a nine-fold improvement of output power compared to a device with no proof mass. The size of the proof mass is also an important factor in determining the output power of the device.

Electrical energy can be harvested from the living plants as a new potential renewable energy source. Characterization of the electrical signal is needed to enable an optimum energy harvesting setup condition. In the present paper, an investigation is conducted to analyze the characteristic of Aloe Barbadensis Miller (Aloe Vera) leaves in terms of electrical energy generation under specific experimental setups. The experimental results show that 1111.55uW electrical power can be harvested from the Aloe Vera with 24 pairs of electrodes and this energy is capable to be stored in a capacitor. This energy has a high potential to be used to power up a low power consumption device.

It is well proven that electrical energy can be harvested from the living plants which can be used as a potential renewable energy source for powering wireless devices in remote areas where replacing or recharging the battery is a difficult task. Therefore, harvesting electrical energy from living plants in remote areas such as in farms or forest areas can be an ideal source of energy as these areas are rich with living plants. The present paper proposes a design of a power management circuit that can harness, store and manage the electrical energy which is harvested from the leaves of Aloe Barbadensis Miller (Aloe Vera) plants to trigger a transmitter load to power a remote sensor. The power management circuit consists of two sections namely; an energy storage system that acts as an energy storage reservoir to store the energy harvested from the plants as well as a voltage regulation system which is used to boost and manage the energy in accordance to a load operation. The experimental results show that the electrical energy harvested from the Aloe Vera under a specific setup condition can produce an output of 3.49 V and 1.1 mA. The harvested energy is being channeled to the power management circuit which can boost the voltage to 10.9 V under no load condition. The harvested energy from the plants boosted by the power management circuit can turn ON the transmitter automatically to activate a temperature and humidity sensor to measure the environmental stimuli periodically with a ton of 1.22 seconds and toff of 0.46 seconds. This proves that this new source of energy combined with a power management circuit can be employed for powering the wireless sensor network for application in the Internet of Things (IoT).

Piezoelectric ceramics are commonly used in various sensing applications. In this paper, the effect of poling and repoling conditions on thick-film piezoelectric ceramics were investigated. The piezoelectric charge coefficient of the piezoelectric ceramics were measured with varying poling conditions, where the effect of changing poling temperature and electrical field on the d 33 were analyzed. This was followed by investigating on the effect high applied electrical fields results in repolarization the alignment of the piezoelectric domain in the opposite direction. The temperature and electrical field dependence polarization of the thick-film piezoelectric ceramics were varied near to its Curie temperature between 50 o C to 250 o C and at a range of electrical field from 20 V (400 kV/mm) up to 200 V (4 MV/mm). It was found that the piezoelectric properties increases with increasing the poling electric field and poling temperature significantly. The maximum values of piezoelectric coefficient were obtained for the piezoelectric ceramics poled at the Curie temperature with high electric fields for 15 min. The aging behavior of the piezoelectric ceramics shows that piezoelectric charge coefficient d 33 depends on the poling and repoling conditions.