This investigation aims to develop an angular stiffness sensor intended for measuring dental implant stability in bone. The sensor hardware included a tiny eccentric motor and an accelerometer to measure a flex constant of an implant with its abutment. The sensor software included a mechanics-based model to convert the flex constant to angular stiffness at the implant/abutment junction to indicate the stability. The sensor’s accuracy and effectiveness are demonstrated through use of Sawbones slab models that mimic a mandibular premolar section. The models include a Branemark Mk III implant inserted into Sawbones slabs of 5 different densities with a locator abutment. An incremental insertion torque was first recorded while the implant was placed in the Sawbones models. Then benchtop experiments were conducted to measure resonance frequencies and angular stiffness. Results indicated that angular stiffness increased with Sawbones density, showing high correlation with the measured resonance frequency ($R=0.977$) and the incremental insertion torque ($R=0.959$). Finally, accuracy of the angular stiffness sensor is calibrated in light of the resonance frequency. Angular stiffness scores 99% and 95% accuracy for Sawbones models mimicking medium cancellous bones with and without a cortical layer, respectively.

Stability of a dental implant reflects quality of osseointegration between the implant and its surrounding bone. While many methods have been proposed to characterize implant stability, angular stiffness at the neck of the implant has been proven to be a rigorous and accurate measure. Nevertheless, fast and reliable measurements of the angular stiffness in a clinical environment are not yet available. This article is to demonstrate a novel stability diagnostic device that can measure the angular stiffness accurately in clinical environments. The device consists of a sensing unit, a controller unit, and a mobile app. In the sensing unit, a coupler attaches a buzzer motor and a tiny accelerometer to an abutment of an implant, whose angular stiffness is to be measured. The buzzer vibrates at a frequency below the resonance frequency of the implant–bone–abutment system. Meanwhile, the accelerometer measures the abutment's vibration. The controller unit powers the buzzer, reads the accelerometer data, and transmits the data to the mobile app. The mobile app postprocesses the data and extracts the angular stiffness through use of a finite element model and a nonlinear regression algorithm. The extracted angular stiffness is compared with a calibrated angular stiffness, which is obtained independently via a force hammer and a laser Doppler vibrometer. The comparison shows reasonable agreement, with the difference being in the range of 4–20%.

A lead-zirconate-titanate (PZT) thin film additively manufactured on a flexible substrate is demonstrated in this paper as an actuator. PZT nano-particles (NPs) are first fabricated via a hydrothermal process. The NPs are then suspended in ethanol with a polymer additive to form PZT ink. The PZT ink is later drop-cast on a flexible substrate with two electrode designs for evaluation: sandwich electrodes and interdigitated electrodes (IDEs). The design of sandwich electrodes is difficult to realize, because silver electrodes cannot be properly printed onto the PZT film with good conductivity and dimension accuracy. In contrast, a pair of IDEs are successfully inkjet printed on a polyethylene terephthalate (PET) tape. Then the PZT ink is drop-cast to form a PZT film. Sinusoidal voltage applied over the electrodes drives the device into resonance serving as a resonator. For hard disk drives, the 3D printed PZT films can be used as dual-stage actuators or as absorbers to actively or passively reduce flex cable vibration.

If the suspension is arranged in the position where the vibration of exhaust system is larger, the vibration transmitted from exhaust system to the body will increase, which will affect the NVH performance of the vehicle. In order to determine the appropriate suspension position of the exhaust system of a passenger car, the finite element model of the exhaust system is established by ANSYS. The suspension point of the exhaust system is arranged by means of ADDOFD. The rationality of the suspension point is verified by static analysis and constrained modal analysis of the exhaust system. The results show that the ADDOFD method is effective in arranging the suspension position of the exhaust system, and the simulation research is of great significance.