Chin-Chung Chen

A Miniature Magnetic-Piezoelectric Thermal Energy Harvester

In this paper, we report a miniature thermal energy harvester with a novel magnetic-piezoelectric design. The harvester consists of a soft magnetic Gd cantilever beam, a piezoelectric lead zirconate titanate sheet, an NdFeB hard magnet, silicon clamps, and a silicon frame. In this design, the harvester is driven by a temperature difference between a cold side and room temperature ambient air, unlike other magnetic-piezoelectric thermal energy harvesters that are driven by a temperature difference between a cold side and a hot side or between two hot sides. Experimental results show that with a temperature difference of 20 °C (cold side: 6.7 °C, hot side: 26.7 °C), the harvester produces a maximum peak-to-peak voltage of 37 mV and a root mean square voltage of 1.98 mV. The estimated maximum instantaneous power density and average power density is 21.7 nW/cm3 and 62.9 pW/cm3, respectively. Moreover, the total volume of our harvester (length × width x height: 6 × 3.5 × 3 mm) is 217 times lower than that of previous experimental harvesters and 38 times smaller than that of previous theoretical-modeled harvesters. Therefore, our harvester is the smallest machined magnetic-piezoelectric thermal energy harvester designed to date. These features enable our harvester to be more easily implemented and integrated with micro wireless sensors and thereby increase more self-powered wireless-sensing applications.

A Three-Axial Frequency-Tunable Piezoelectric Energy Harvester Using a Magnetic-Force Configuration

To date, researchers have utilized energy harvesters to power wireless sensor nodes as self-powered wireless sensors to create many innovative wireless sensors network applications such as medical monitoring, machining-condition monitoring, and structural-health monitoring. Regarding to energy harvesters, some researchers demonstrated wideband or frequency up-converted vibrational energy harvesters using magnetic force together with piezoelectric materials. However, these harvesters are not able to harness 3-D or three-axial mechanical energy through using one single mechanism or configuration. To address this problem, we report a novel magnetic-force-configured three-axial frequency-tunable piezoelectric energy harvester in this paper. Due to the magnetic-force configuration, the harvester converts ambient three-axial mechanical vibration/motion to piezoelectric voltage-response (i.e., three-axial energy harvesting). Simultaneously, the harvester also converts the ambient vibration/motion at a lower frequency to higher frequency without mechanical wear-out (i.e., noncontact frequency up-conversion). Through modifying the configuration, the oscillating frequency is tunable. By frequency tuning, the harvesters oscillating frequency and ambient vibration frequency are able to be matched to maximize the power output. Experimental results show the peak voltage, peak power, and frequency conversion of one single piezoelectric beam of the harvester under an in-plane and out-of-plane vibration is up to 800 mV, 640 nW, and from 7 to 56 Hz, and 27 mV, 729 pW, and from 1 to 294 Hz, respectively. These results confirm the harvester is capable of harnessing energy from 3-D and three-axial mechanical motion/vibration, addressing frequency-mismatching issue, avoiding mechanical wear-out problems, and producing a stable voltage output. Due to these, the energy-harvesting approach will enable more novel and practical wireless sensors network applications in the future.

A Miniature Mechanical-Piezoelectric-Configured Three-Axis Vibrational Energy Harvester

In this paper, we demonstrate a novel robust miniature three-axis vibrational energy-harvester using a mechanical-piezoelectric configuration. Using the configuration, the harvester employs Newtons law of inertia and the piezoelectric effect to convert either the x-axis or y-axis in-plane and z-axis out-of-plane ambient vibrations into piezoelectric voltage-responses. Under the x-axis vibration (sine-wave, 75 Hz, 3.5 g), our modeled, finite-element analyzed/simulated, and experimental root mean square voltage-response with power-outputs of the harvester (stimulated in resonant with the optimum load) is 525.36 mV with 0.477 μW, 516.51 mV with 0.461 μW, and 548 mV with 0.519 μW, respectively. Under the z-axis vibration (sine-wave, 95 Hz, 3.8 g), the modeled, finite-element analyzed/simulated, and experimental root mean square voltage-response with power-output of the harvester (stimulated in resonant with the optimum load) is 157.35 mV with 0.066 μW, 170.25 mV with 0.0772 μW, and 168 mV with 0.075 μW, respectively. These show that not only both of our modeling and finite-element analysis/simulation can successfully predict the experimental results, but also our harvester is capable of harnessing three-axial ambient vibrations. Moreover, through the piezoelectric lead-zirconate-titanate-connected-inseries approach, the voltage and power outputs are increased. According to these achievements, we believe that our harvester would be an important design reference in industry for future development of microfabrication-based (MEMS-based) three-axial piezoelectric energy harvesters and accelerometers.

Electromagnetic/Magnetic-Coupled Targeting System for Screw-Hole Locating in Intramedullary Interlocking-Nail Surgery

At present, intramedullary interlocking nails are widely used for bone-fracture fixation in orthopedic surgeries. Surgeons often use X-ray imaging to find the actual location of the distal screw-holes of the nail after the nail is inserted into the medullary canal of a bone for fixation. Thus, the patients and medical team are inevitably exposed to radioactivity. In this paper, we report a radiation-free electromagnetic/magnetic-coupled targeting system to locate the distal screw-holes of the nail used in interlocking-nail surgery. The targeting system consists of a c-shaped electromagnet with a pick-up coil, a highly permeable curved silicon-steel strip embedded on the nail, a guiding mechanism, and electronic measuring instruments. An alternative current is applied to the electromagnet to generate a uniform magnetic field/flux in the electromagnets air gap. When the nail inserted into the medullary canal of a bone is scanned through or rotated in the air gap of the electromagnet, the magnetic flux in the air gap is influenced by the silicon-steel strip embedded on the nail. The variation of the magnetic flux induces a voltage response in the pick-up coil due to electromagnetic induction. The pattern of the voltage response is analyzed to establish a criterion for screw-hole targeting. The results obtained using this criterion reveal that the maximum targeting error of the location and orientation targeting for a screw-hole with a diameter of 5 mm is <;2 mm and 10°, respectively. Thus, the system/approach is sufficiently simple and accurate to be used by surgeons in clinical surgery.

A Novel Thermomagnetic Rotational-Actuator

In this article, we demonstrate a novel thermomagnetic rotational-actuator. The actuator consists of thermomagnetic material Gadolinium sheets, thermoelectric generators, a rotary aluminum cantilever beam with NdFeB hard magnets fixed on the free-end of the beam, a stainless steel bearing, and a mechanical frame. As conventional magnetic rotational-actuators are controlled by using electromagnetic-induction-based magnetic-force interaction produced by electromagnets or coils, our actuator is controlled by using a heating-induced magnetic force interaction produced by the thermomagnetic generators. Experimental results show that our actuator is successfully rotated by a controlled sequence of temperature-difference generated by the TEGs.Copyright

A Rotational Actuator Using a Thermomagnetic-Induced Magnetic Force Interaction

In this paper, we demonstrate a rotational actuator using a thermomagnetic-induced magnetic force interaction. The actuator consists of a magnetic rotary beam, stainless-steel bearing, mechanical frame, thermomagnetic Gadolinium sheets, and thermoelectric generators (TEGs). Experimental results show that applying a sequence of currents to the TEGs successfully produces sequential magnetic forces. Consequently, these sequential magnetic forces rotate the beam for revolutions. When applying a sequence set of currents of −0.5 and 1.3 A, the maximum rotation speed and maximum stall torque of the actuator is 3.81 rpm and

A Novel Thermomagnetic-Actuated Gripper With a Piezoelectric–Pyroelectric Sensing Readout of Gripping States and Forces

136.2~\mu

A Novel Mechanical-Mechanism Enhanced Thermomagnetic Tweezer Demonstrating Gripping of Ferromagnetic and Non-Ferromagnetic Objects

Nm, respectively. Most importantly, the operating temperatures of other thermomagnetic (and electrothermal) actuators are usually high, but the operating temperature of our actuator is approximately room temperature (13 °C–27 °C). Therefore, our actuators have more practical applications. According to the above-mentioned features, we believe our actuator is an important alternative approach to developing future rotational actuators and motors.

Design, Fabrication, and Testing of a Thermal/Mechanical/Magnetic Hybrid Energy Micro-Harvester

In this paper, we reported a thermomagnetic-actuated gripper with a piezoelectric–pyroelectric sensing readout of gripping states and forces. The gripper consists of two CuBe cantilever beams, a Gd sheet, NdFeB hard magnets, a thermoelectric generator (TEG), a piezoelectric–pyroelectric PZT sheet, and a polymer-polymethyl methacrylate base. When TEG cools the Gd sheet lower than its Curie temperature, the magnetic attraction between the Gd sheet and the NdFeB magnets is produced due to the thermomagnetic property of the Gd sheet. Subsequently, the magnetic attractive force deflects two beams until beams contact to each other. Thus, the gripper can grasp a small object. Furthermore, when the gripper is operated to grasp the object, the piezoelectric–pyroelectric PZT sheet of the gripper produces voltage response. Through analyzing the voltage response, the gripping state is detected and subsequently the gripping force is obtained. After gripping, a negative dc current is applied to TEG to heat the Gd sheet higher than Gd’s Curie temperature. Due to this, the magnetic attractive force is reduced and eventually eliminated. Consequently, the beams are separated due to their spring-back force. Thus, the gripper releases the object. The experimental results show that the gripper can be sequentially operated to grasp and release the object. Furthermore, as the current applied to the TEG is increased, the gripping force is increased. The maximum gripping force of the gripper is 0.69 N when a dc current of 0.7 A is applied. Moreover, when comparing conventional magnetic-field-actuated magnetic grippers, our gripper can be individually operated by applied currents, detect the gripping state, and sense the gripping force.

Optical properties of a novel yellow fluorescent dopant for use in organic LEDs

In this article, we demonstrate a mechanical-mechanism enhanced thermomagnetic tweezer. The tweezer which utilizes a thermal-magnetic-mechanical converting consists of two cross-jointed Al arms, two Gd sheets, two NdFeB hard magnets, two thermoelectric generators (TEGs), and a ball bearing set. When comparing conventional thermomagnetic grippers, our thermomagnetic tweezer can grip either ferromagnetic or non-ferromagnetic objects and avoid producing temperature-influence to the gripped objects. Experimental results show that we can control TEGs to generate a temperature difference to operate the tweezer to grip small ferromagnetic objects (such as NdFeB hard magnet) and other non-ferromagnetic objects (such as PMMA bulk). The maximum gripping force produced by the tweezer operated by applying the DC current of 1.3 A with the voltage of 0.85 V is 0.59 newton. The corresponding gripping and releasing duration is 7.9 seconds and 8.1 seconds, respectively. According to these results, our tweezer would produce more practical objects-gripping applications.Copyright