RESUMO
The longstanding demands for micropressure detection in commercial and industrial applications have led to the rapid development of relevant sensors. As a type of long-term favored device based on microelectromechanical system technology, the piezoresistive micropressure sensor has become a powerful measuring platform owing to its simple operational principle, favorable sensitivity and accuracy, mature fabrication, and low cost. Structural engineering in the sensing diaphragm and piezoresistor serves as a core issue in the construction of the micropressure sensor and undertakes the task of promoting the overall performance for the device. This paper focuses on the representative structural engineering in the development of the piezoresistive micropressure sensor, largely concerning the trade-off between measurement sensitivity and nonlinearity. Functional elements on the top and bottom layers of the diaphragm are summarized, and the influences of the shapes and arrangements of the piezoresistors are also discussed. The addition of new materials endows the research with possible solutions for applications in harsh environments. A prediction for future tends is presented, including emerging advances in materials science and micromachining techniques that will help the sensor become a stronger participant for the upcoming sensor epoch.
RESUMO
Microcontact force measurement is widely applied in micro/nano manufacturing, medicine and microelectromechanical systems. Most microcontact force measurements are performed by using mass comparators, nano-indenter and precision electronic balance, and weighing sensors. However, these instruments have a complex structure and high cost. Nevertheless, the rapid development of microsensor technology provides a new, simple and low-cost approach for microcontact force measurement. In this study, we present a method of microcontact force measurement by using micropressure sensors and study the relationship amongst the microcontact force, output voltage and contact position of the sensor. We use a microcapacitance pressure sensor as an example, then we perform a simulation calculation and construct a microcontact force experiment system to verify the simulation results. The experimental and simulation results are consistent. In addition, an equation that describes the relationship amongst the microcontact force, output voltage and contact position of the sensor is obtained. Based on this simple and low-cost method, we build a micro-manipulation system, which indicates that the micropressure sensors can be used to measure microcontact force in various applications easily and cost-effectively. Furthermore, it is considerably relevant to research and application in this field.
RESUMO
Implantable pressure biosensors show great potential for assessment and diagnostics of pressure-related diseases. Here, we present a structural design strategy to fabricate core/shell polyvinylidene difluoride (PVDF)/hydroxylamine hydrochloride (HHE) organic piezoelectric nanofibers (OPNs) with well-controlled and self-orientated nanocrystals in the spatial uniaxial orientation (SUO) of ß-phase-rich fibers, which significantly enhance piezoelectric performance, fatigue resistance, stability, and biocompatibility. Then PVDF/HHE OPNs soft sensors are developed and used to monitor subtle pressure changes in vivo. Upon implanting into pig, PVDF/HHE OPNs sensors demonstrate their ultrahigh detecting sensitivity and accuracy to capture micropressure changes at the outside of cardiovascular walls, and output piezoelectric signals can real-time and synchronously reflect and distinguish changes of cardiovascular elasticity and occurrence of atrioventricular heart-block and formation of thrombus. Such biological information can provide a diagnostic basis for early assessment and diagnosis of thrombosis and atherosclerosis, especially for postoperative recrudescence of thrombus deep within the human body.