Showing papers by "Jianping Liu published in 2023"

A Bionic Type Piezoelectric Actuator Based on Walking Motion and Asymmetrical L-Shaped Flexure Mechanisms

Abstract: A bionic type piezoelectric actuator based on the walking motion of L-shaped flexure mechanisms has been proposed. By mimicking the walking motion of “human legs,” the proposed actuator is able to not only eliminate the backward motion to improve the motion efficiency, but also achieve the large working stroke with high output load easily. The special L-shaped flexure mechanism is employed as the “leg,” and the bionic walking motion is realized by applying two L-shaped flexure mechanisms alternately. The driving principle of the proposed piezoelectric actuator is discussed in detail, and the simulation is carried out to study the feasibility. An experimental system has been set up to investigate the actual working performance. According to the experimental results, the suitable phase difference between the two L-shaped flexure mechanisms to eliminate the backward motion is around θ = 5°, the maximum speed is V = 1887.3 μm/s, the minimum stepping distance is 0.084 μm, and the maximum load is more than Fv = 1100 g. The motion speed and the maximum load under the proposed bionic walking motion (two flexure mechanisms work together as “legs”) could be improved greatly for almost 3.7 and 1.7 times, respectively, compared with that of the traditional friction–inertial motion (only one flexure mechanism works). By eliminating the backward motion, the motion efficiency is improved about 52.9% under the condition of 120 V and 1 Hz. This article shows the feasibility of applying the bionic motion to improve the performance of piezoelectric actuators, which may be instructive for the design of piezoelectric actuators with large working stroke. In the future, it may be helpful for the real application of piezoelectric actuators in the fields of ultraprecision machining, optical engineering, and aerospace technology.

The Development of Piezoelectric Inchworm Actuator Clamped With Magnetorheological Elastomer and Its Potential Application in Brain–Computer Interface Implantation

Abstract: The piezoelectric inchworm actuator with high-positioning accuracy and large output force is a potential device to implant microelectrode in the invasive brain–computer interface (BCI). However, the traditional piezoelectric inchworm actuator adopts multichannel electrical control signals from external equipment and rigid-to-rigid friction contact to drive, resulting in complex control and uneven friction. To solve the above problems, in this article, magnetorheological elastomer (MRE) is first proposed as the clamping material of the piezoelectric inchworm actuator. An MRE–capillary–cover sandwich structure is adopted to achieve rigid-to-elastomeric clamping. The driving and clamping actions of the actuator are controlled by two cam mechanisms mounted on the same shaft, and a battery can feed the actuator. A kinetic model is established to analyze and predict the actuator motion. Several crucial clamping parameters are explored, and the performance experiments are conducted to evaluate actuator characteristics. A verification experiment is carried out to prove the feasibility of the microelectrode implantation in the pig brain (0.6% agarose gel). The actuator can reach the maximum velocity of 1250.4 μm/s and the maximum output force of 420 mN; in the forward/backward motion, the minimum step is 0.5837/0.5912 μm, and the repeatability is 0.0465/0.0469 μm; thus, the actuator has great application potential in BCI.

An Inchworm and Stick-slip Dual Mode Piezoelectric Linear Actuator for Cell Injection

Abstract: Cell injection system for biomedical engineering demands that actuators have large stroke, high resolution and speed for cell positioning and injection. Single mode piezoelectric actuators could meet some of these requirements but hardly all. Stick-slip actuator is easy to achieve high-speed operation, but it is prone to setback; The speed characteristics of the inchworm actuator are lower than those of the stick-slip actuator, but the step is more stable and the setback is lower. This study proposes an inchworm and stick-slip dual mode piezoelectric actuator (ISSPA) for cell injection. It integrates two working modes into one actuator and both modes drive the same slider. The stick-slip mode works at high frequency for fast positioning to the cell and the inchworm mode drives the needle to puncture the cell membrane and accurately locates to the specified location. The structure and working principle of the ISSPA are provided. A prototype of the proposed ISSPA is fabricated and experiments are conducted. When the driving voltage of the piezoelectric stack is 100 V and the frequency is 500 Hz,the maximum speed of the ISSPA is 2.287 mm/s in the stick-slip mode. When the driving voltage of the piezoelectric stack is 60 V, the frequency is 3 Hz and the load is 0.5 kg,the minimum step displacement is 57 nm in inchworm mode. Demonstration of cell injection is carried out by using the ISSPA to positioning and puncturing a zebrafish embryo. Fast positioning with the stick-slip mode and accurate puncture with the inchworm mode are achieved with the ISSPA alone, taking 12 seconds for the whole injection process. It could be expected to apply the ISSPA to cells with wide range of diameter, as the frequency of the stick-slick mode and the voltage of the inchworm mode could be well regulated.

An Optimization Algorithm H-GVSPM for Electrical Impedance Tomography

Abstract: Electrical impedance tomography (EIT) is a novel industrial monitoring technology with the characteristics of safety, inexpensiveness, and real-time monitoring. Its imaging results are easily to generate artifacts due to the influence of various factors. Therefore, the image quality is low, and the contour of measured objects has a distortion phenomenon. An optimization algorithm H-GVSPM based on the Hadamard product is proposed for EIT to reduce the artifacts, and to improve the image quality. The relative conductivity difference between the measured object and the background becomes more distinguishable with the action of the Hadamard product. Simulation and experimental results show that H-GVSPM effectively reduces the influence of artifacts in the reconstructed images. The maximum increase of the correlation coefficient approximately is 15.56% and 22.80% respectively compared with GVSPM and TV method. The maximum reduction of the voltage relative residual is 22.12% in the simulation, and it is 8.12% in the experiment. The standard deviation of conductivity is about 1/10 of the original. This study provides a reference method for improving image quality, and it contributes to the application of EIT in industry, biomedicine, and other fields in the future.

Quasi-opsonin conjugated lipase-sensitive micelles activate macrophages against facultative intracellular bacterial infection.

Abstract: Drug resistance caused by facultative intracellular bacteria such as Salmonella typhimurium (S. typhimurium) is still a tough challenge. Bacteria phagocytosed by macrophages have evolved a variety of mechanisms to defend against host attack, and the poor entry of antibiotics into infected macrophages is conducive to the survival of intracellular bacteria. In this report, we prepared a quasi-opsonized chloramphenicol (Chl)-loaded micellar system (B-mLBP-M/Chl) assembled by a bacterial lipase-sensitive polymer with a conjugate of lipopolysaccharide-binding protein (LBP) analog and biotin (B) as a ligand, which could eliminate drug-resistant S. typhimurium with quasi-opsonization via 3 steps: (i) target and release antibiotics on bacteria lipase, (ii) opsonize S. typhimurium to be digested by the macrophage, and (iii) activate the macrophage for fighting. The B-mLBP-M/Chl could target bacterial LPS through mLBP by simulating the N-terminal sequence of native LBP, exhibiting a high ability to target the localized infection site in mice. It could also activate the phagocytosis of macrophages via coupled biotin, cooperating with antibiotics and effectively improving the survival of mice with little pathological damage to tissues. Moreover, compared with native opsonin, B-mLBP does not cause an excessive inflammatory response and could recover homeostasis after exerting the quasi-opsonization by regulating the levels of pro-inflammatory cytokines and anti-inflammatory cytokines. With a universal target site for Gram-negative bacteria and macrophage activation, this B-mLBP-M/Chl could be applied to other bacterial infections in the future. In particular, this analog may also serve as a useful template to design safe artificial opsonin, which could be a ligand for drug delivery systems or prodrugs.

A parasitic-inertia piezoelectric actuator with isosceles trapezoidal flexible mechanism base on parasitic motion exploration and asymmetrical installation

Abstract: Parasitic-inertia piezoelectric actuators have been widely studied for their ability to achieve both high positioning accuracy and large working strokes. However, backward motion results in parasitic-inertia piezoelectric actuators with the disadvantages of low efficiency and abrasion of driving foot. In this study, a parasitic-inertia piezoelectric actuator with an isosceles trapezoidal flexible mechanism is diegned and optimized to reduce backward motion considering the influence of parasitic motion proportion. It applies the asymmetrical installation of the piezoelectric stack to increase parasitic motion hence the reducing of backward motion. This study discusses the structure and working process of piezoelectric actuators and optimizes the design of flexible mechanism structure parameters with matrix displacement method and finite element method. A prototype of an parasitic-inertia piezoelectric actuator was manufactured, and a series of experiments were conducted. From the experiment, the piezoelectric actuator obtained a minimum backward motion percentage α = 18.36% and forward motion time percentage β = 95.9% at the frequency f = 1 Hz and the voltage U = 80 V. At U = 120 V, f = 500 Hz, the maximum motion speed of the actuator is 916 μm s−1; At U = 20 V and f = 1 Hz, the minimum positioning resolution of the actuator is 0.69 μm. At U = 120 V, f = 1 Hz, the maximum vertical load force is 1600 g, and the maximum parallel load force is 50 g. It has shown that the proposed isosceles trapezoidal flexible mechanism is feasible and can significantly reduce backward motion at the appropriate voltage. The mentioned characteristics of isosceles trapezoidal flexible mechanism can significantly alleviate the abrasion of driving foot, improve working efficiency. Also, it is vital for the miniaturization and practical application of parasitic-inertia piezoelectric actuators.