In this paper, a resonant-type piezoelectric inertial motor driven by rectangular pulse is developed. The rectangular pulse drive methodology is explained and its influence on output displacement of the stator is discussed in relation to four factors: frequency ratio, duty ratio, vibration amplitude ratio, and phase difference. A bending stator with second harmonics at its double fundamental resonant frequency is designed to generate saw-tooth type displacements under a rectangular pulse. It is composed of an aluminum plate (20mm×4mm×2mm) sandwiched between two piezoelectric plates (10mm×4mm×0.73mm). Experiments show that with optimized duty ratios, both the rotation speed and stall torque can be enhanced. The rotation direction of the rotor can be reversed by changing the duty ratio. The maximum no-load angular speed reaches 300rpm with driving voltage of 60Vpp at the fundamental resonant frequency of 35.3kHz in both directions. Using a preload of 1.6N, stall torque reaches 1220 µNm driven at 80Vpp and 35.3kHz. The maximum power density and efficiency of the motor are 4.2μW/mm 3 and 2.1%, respectively,
Large cutaneous wounds pose a severe medical problem and may be deadly in cases when regeneration is impaired. Recently, topical stem cell therapy has been realized as a promising strategy for wound healing and skin regeneration. However, stem cells must be administrated uniformly to the wound area, otherwise treatment will be ineffective, which has been a limitation of current administration methods. Specifically, the delivery pressure and nozzle features of most clinical cell spray devices are unknown, which may significantly affect the viability of sprayed cells and their capacity for proliferation. Herein, we developed a novel pneumatically assisted atomization device (PAAD) in which cell suspensions were uniformly atomized at a low delivery pressure. We optimized the applied fluidic pressure and air pressure to maximize cell survival and function for the application of multiple cell types, while ensuring uniform dispersal across the wound site. Moreover, we found that the application of sprayed umbilical cord-derived mesenchymal stem cells to wound sites significantly accelerated wound healing and promoted appendage regeneration on an excisional cutaneous wound model. Overall, the novel PAAD system delivered living cells uniformly and maintained the viability and differentiation of sprayed cells, strongly suggesting its potential for application in clinical cell therapy, especially for large, irregular, and severe skin wounds.
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