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To achieve a wide operating velocity range, stepping without backward motion, and high positioning resolution, a walking-type piezoelectric actuator with compliant mechanisms is developed. There are few academic research reports on this type of actuator, and this paper clarifies the features and advantages of this actuator. A systematic modeling and experimental evaluation of the proposed actuator are carried out. First, the configuration of the proposed actuator and the working principle of the alternating elliptical movements of the two driving feet are described. Then, dynamic models are built to simulate the output characteristics of the proposed actuator with in-phase and opposite-phase drive, which provide guidance for the design and optimization of walking-type actuators. An actuator prototype is fabricated and experimentally evaluated. The experimental results indicate that, under the opposite-phase drive, the proposed actuator can operate at a driving frequency of 1–15000 Hz. At a frequency of 14000 Hz, a maximum velocity of 24.6 mm/s is achieved at a voltage of 36 V pp , and the dead zone of the actuator is 0–6 V pp. A step displacement of 2.25 μm without backward motion is accomplished at a voltage of 72 V pp and a frequency of 1 Hz. Furthermore, the positioning resolution in the forward and reverse directions are 144 and 152 nm, respectively. The repeatability of the actuator is ±25 to ±50 nm for strokes of 325–725 nm, respectively. Therefore, compared to two driving feet being driven in phase, driving them in opposite phase as if they were walking has been confirmed to increase thrust, shorten the rise time, reduce the dead zone of driving voltage, eliminate backward motion, and provide high repeatability. • A piezoelectric actuator with triangular compliant mechanisms is first developed. • Dynamic models in the x - and y -directions are established for performance evaluation. • The actuator achieves a wide operating velocity range, no backward motion, and high-precision positioning. [ABSTRACT FROM AUTHOR]

Insulin aspart (IAsp) and insulin degludec (IDeg), as the third generation of insulin, have a faster onset time or a more durable action period, which may simulate the secretion of insulin under physiological conditions. Microneedles (MNs) are transdermal delivery devices that may allow diabetic patients to easily deploy transdermal insulin therapy while considerably reducing injection pain. In this study, we investigated the combination of dissolving MNs with IAsp or IDeg therapy as an alternative to daily multiple insulin injections, aiming to improve glycemic control and patient compliance. Mechanical properties of the MNs, structural stability of insulin encapsulated in the MNs, and transdermal application characteristics were studied to assess the practicality of insulin-loaded MNs for diabetes therapy. In vivo experiments conducted on diabetic rats demonstrated that the IAsp- and IDeg-loaded MNs have comparable blood glucose control abilities to that of subcutaneous injections. In addition, the therapeutic properties of insulin-loaded MNs under diverse dietary conditions and application strategies were further investigated to provide new information to support future clinical trials. Taken together, the proposed MNs have the potential to improve balances between glycemic control, hypoglycemia risk, and convenience, providing patients with simpler regimens. 1. The fabricated functional insulin-loaded dissolving microneedles closely matched the glucose rise that occurs in response to meals, demonstrating promising alternatives for multiple daily insulin injections. 2. The hypoglycemic properties of insulin microneedles were investigated under diverse dietary conditions and application strategies, yielding new information to support future clinical trials. 3. Molecular dynamics simulations were utilized to study the interactions between the insulin and microneedle matrix materials, providing a strategy for theoretically understanding drug stability as well as the release mechanism of drug-loaded microneedles. [Display omitted] [ABSTRACT FROM AUTHOR]

By using the prominent merit of poly(N -isopropylacrylamide) (PNIPAm) that can reversibly switch from a linear state to a coiled state with the change in temperature, in this work, gelatin was grafted with carboxylic end-capped PNIPAm as the matrix material to fabricate a physical entanglement crosslinked hydrogel microneedles (MNs) patch that can control drug release after application on the skin. The crystallization of the drug during the fabrication process of MNs was decreased due to the thermo-reversible sol-gel transition of the matrix materials. In addition, to increase the mechanical strength of the MNs and to decrease the application time, the gelatin-g-PNIPAm (GP) MNs patch was mounted onto solid MNs to fabricate a rapidly separating MNs system (RS-GP-MNs). The combination of the rapidly separating technique and the thermosensitive hydrogel provides the combined ability to efficiently deliver drug-loaded MNs into the skin within few seconds and to control drug release within the skin. Through a series of tests, we found that RS-GP-MNs showed suitable lower critical solution temperature and adequate crosslinking speed for practical application. The hypoglycemic effect in diabetic mice was characteristically controlled by insulin release through RS-GP-MNs as compared to the MNs made from unmodified gelatin. The proposed RS-GP-MNs system is potentially applicable to various hydrophilic small molecular and peptide medicines that require frequent dosing, thus providing an effective, noninvasive, and painless administration method with minimal safety concerns. 1. Hydrogel microneedles that can be reversibly triggered and controllably release drugs at body temperature were fabricated. 2. Hydrogel microneedles prepared from gelatin-g-PNIPAm can avoid the use of a molecular crosslinker that is toxic and difficult to be completely removed. 3. Gelatin-g-PNIPAm with thermosensitive property showed appropriate molecular interactions with the drug and slowed down the crystallization speed of the drug in the solution. [Display omitted] [ABSTRACT FROM AUTHOR]

To realize the performance of large stroke, smooth motion with less wear, and high positioning resolution, a non-resonant piezoelectric linear actuator based on a parallel-arrangement dual stator was developed in this study. The proposed actuator could achieve the multi-drive mode with different voltage signals, including co-drive, alternate-drive, and precision positioning mode. A prototype was fabricated, and a series of experiments were tested to evaluate its output performance under three driving modes. The experimental results indicated that, under the alternate-drive mode, when a voltage of 50 V p-p and a preload of 8.6 N were applied to the proposed actuator, a no-load speed of 0.06–1.2 mm/s at driving frequencies of 10–500 Hz and a stepping displacement of 1.8 μm at 1 Hz were achieved; A maximum thrust of 7.3 N at 100 Hz and a maximum no-load speed of 16.1 mm/s at 3000 Hz were obtained under a voltage of 100 V p-p and a preload of 20.8 N. Moreover, under the precision positioning mode, the nanoscale positioning resolutions of 156 and 172 nm in forward and reverse motions were achieved, respectively. Thus, the proposed actuator is expected to be applied for driving the aperture of a scanning electron microscope. [Display omitted] • A piezoelectric actuator based on a parallel-arrangement dual stator was developed. • The operating principles of co-drive, alternate-drive, and precision positioning modes were proposed. • The characteristics of thrust, speed, and positioning resolution of the proposed actuator were evaluated. [ABSTRACT FROM AUTHOR]

Dynamic ensemble selection (DES) effectively improves aggregation performance by dynamically finding the most appropriate subset of classifiers for each query sample. The key component of this strategy is to define an appropriate criterion for evaluating the competence of the candidate classifiers. In this study, we present a new group-based criterion, synergy competence, to comprehensively measure the magnitude of the intricate synergy effect among classifiers. In addition, we introduce the algorithm Shapley, a variant of the Shapley value (SV) in the game theory, to measure the synergy competence of each classifier, which helps in the construction of a synergy-based DES system, called DES-AS. We argue that candidate classifiers with positive algorithm Shapley should be selected as they contribute to the ensemble. After selecting a subset of classifiers, the normalized algorithm Shapley is employed to calculate the voting weights for a cooperative final classification decision. The experimental analyses conducted on forty real-world datasets not only indicate that the synergy competence estimated by the algorithm Shapley is more applicable than classic group-based metrics, but also show that DES-AS is substantially more effective and robust than state-of-the-art models. The statistical test results also indicate that the estimated synergy competence reflects the real competence of each classifier better than the baseline models. • A new generalized group-based selection criterion, synergy competence, is introduced. • An algorithm Shapley is proposed to assess candidate classifiers' synergy competence. • A new dynamic ensemble selection method is developed based on algorithm Shapley. • A thorough empirical study is conducted to analyze the performance of DES-AS. [ABSTRACT FROM AUTHOR]