Flexo-Ionic Effect of Ionic Liquid Crystal Elastomers

The first study of the flexo-ionic effect, i.e., mechanical deformation-induced electric signal, of the recently discovered ionic liquid crystal elastomers (iLCEs) is reported. The measured flexo-ionic coefficients were found to strongly depend on the director alignment of the iLCE films and can be over 200 µC/m. This value is orders of magnitude higher than the flexo-electric coefficient found in insulating liquid crystals and is comparable to the well-developed ionic polymers (iEAPs). The shortest response times, i.e., the largest bandwidth of the flexo-ionic responses, is achieved in planar alignment, when the director is uniformly parallel to the substrates. These results render high potential for iLCE-based devices for applications in sensors and wearable micropower generators.

Analytical, FEA, and Experimental Comparisons of Piezoelectric Energy Harvesting Using Engine Vibrations

Piezoelectric elements can be used as sensors and actuators in flexible structures. In this paper, using the most basic concepts of piezoelectric micropower generators, all useful mathematical equations for getting analytical output are discussed and derived for different piezo positions on cantilever beam and then 3D finite element modeling and simulation of generalized piezoelectric laminated beam problem with proper specifications and properties are done in ANSYS12.0. Experimental analysis is also done on the very practical problem to harvest energy (to get electric energy) by applying some deflection (mechanical energy) on piezo-bonded aluminum beam, that is, to harvest energy (at microlevel at least) by using vibrations of 4-stroke car diesel engine with mounting of piezo cantilever beam. Here piezoelectric beam is used to measure the charge generated from the engine vibrations. The vibration amplitudes are measured with a Laser Vibrometer with considerations of maximum number of power cycles is to be covered for analysis. The vibration response data of displacement of the cantilever at free end measured from Vibrometer are considered for harmonic and analytical analyses as mean displacement amplitude of 3.98 mm at free end. The study further carried out for effect of different piezo positions and various engine speeds also. Then comparison is also done among obtained results from these three analyses to get validation of all derived mathematical equations.

Micropower Generators and Sensors Based on Piezoelectric Polypropylene PP and Polyvinylidene Fluoride PVDF Films - Energy Harvesting from Walking

This paper presents investigation of piezoelectric proprieties of polypropylene PP and polyvinylidene fluoride PVDF films at an angle of their application as micropower generators and foot pressure sensors in walking process. Obtaind micropower from single layer is about 1.7W and 5.3W for polypropylene film and about 1.7W and 3.3W for polyvinylidene fluoride film. Obtained voltage from single film layer is 8.9V to 14V for PP film and 2 to 3.4V for PVDF film. Obtained micropower from piezoelectric film and course character of voltage in function of time during walking process, depends from used film and shoe insole construction, where active element was sandwich. Recived data record of voltage, power and foot movement images from measuring system, can be use in dynamic investigations of posture defects.

Output Power Optimization for Electromagnetic Vibration Energy Harvesters

In this work, we present a procedure to optimize the output power of electromagnetic vibration energy harvesters, or micropower generators (MPGs). The procedure is based on optimizing both the electrical damping coefficient and the coil configuration, wire gauge and number of turns, to maximize the power flow from the input mechanical source to the electrical load for different load values. Also, we present a closed analytical form for the maximum efficiency of the electromagnetic MPGs.

Experimental Response of Simple Gas Hybrid Bearings for Oil-Free Turbomachinery

Gas film bearings offer unique advantages enabling successful deployment of high-speed microturbomachinery (<0.4 MW). Current applications encompass micropower generators, air cycle machines and turbo expanders. Mechanically complex gas foil bearings are in use; however, their excessive cost and lack of calibrated predictive tools deters their application to mass-produced systems. The present investigation provides experimental results for the rotordynamic performance of a small rotor supported on simple and inexpensive hybrid gas bearings with static and dynamic force characteristics desirable in high-speed turbomachinery. These characteristics are adequate load support, stiffness and damping coefficients, low friction and wear during rotor startup and shutdown, and most importantly, enhanced rotordynamic stability. The test results evidence the paramount effect of feed pressure on early rotor lift-off and substantially higher threshold speeds of rotordynamic instability. Higher supply pressures also determine larger bearing direct stiffnesses, and thus bring an increase in the rotor-bearing system critical speed albeit with a reduction in damping ratio.