The ancient art of origami, traditionally used to transform simple sheets into intricate objects, also holds potential for diverse engineering applications, such as shape morphing and robotics. In this study, it is demonstrated that one of the most basic origami structures–a rigid, foldable degree-four vertex–can be engineered to create a crawler capable of navigating complex paths using only a single input. Through a combination of experimental studies and modeling, it is shown that modifying the geometry of a degree-four vertex enables sheets to move either in a straight line or turn. Furthermore, it is illustrated that leveraging the nonlinearities in folding allows the design of crawlers that can switch between moving straight and turning. Remarkably, these crawling modes can be controlled by adjusting the range of the folding angle's actuation. This study opens avenues for simple machines that can follow intricate trajectories with minimal actuation.

Bistable mechanisms are prevalent across a broad spectrum of applications due to their ability to maintain two distinct stable states. Their energy consumption is predominantly confined to the process of state transitions, thereby enhancing their efficiency. However, the transition often requires two distinct digital inputs, implicating the requirement of multiple actuators. Here, we propose an elastic and contactless design strategy for inducing state transitions in bistable mechanisms, requiring only a single digital input. The strategy leverages internal information, interpreted as system state, as an extra input to make a weighted decision for transitioning to the subsequent state. We characterize the behavior using a spring-based rigid-body model, consisting of a column near bifurcation, combined with a non-linear spring connected to a bistable element that represents the information state. The results show that a nonlinear spring with a quadratic stiffness function, i.e., representing internal instability, is crucial for regulating state-switching behavior. We then demonstrate this design strategy by developing a monolithic and compliant design embodiment and experimentally evaluate its behavior.

The ability to convert reciprocating, i.e., alternating, actuation into rotary motion using linkages is hindered fundamentally by their poor torque transmission capability around kinematic singularity configurations. Here, we harness the elastic potential energy of a linear spring attached to the coupler link of four-bar mechanisms to manipulate force transmission around the kinematic singularities. We developed a theoretical model to explore the parameter space for proper force transmission in slider-crank and rocker-crank four-bar kinematics. Finally, we verified the proposed model and methodology by building and testing a macro-scale prototype of a slider-crank mechanism. We expect this approach to enable the development of small-scale rotary engines and robotic devices with closed kinematic chains dealing with serial kinematic singularities, such as linkages and parallel manipulators.

This work presents a novel design, model and prototype of a motion energy harvester based on bi-stability and frequency up-conversion. The Parametric Frequency up-converter Generator (PFupCG). The PFupCG was designed to harvest energy under conditions where the amplitude of the driving motion is larger than the internal displacement limit. Instead of an impact member, the PFupCG uses a compliant suspension mechanism that combines a bi-stable characteristic with a strong stiffening behavior as a result of geometric effects. This resulted in a prototype of the PFupCG with an internal-to-applied motion amplitude ratio of 0.2. A case study was carried out where the PFupCG was analyzed by simulation and experiment for vibration conditions representative of human walking motion (2Hz, 25 mm).

Microtransmission mechanisms made of elastic materials present an opportunity for exploring scalable mechanical systems integrated with sophisticated functionalities. This paper shows how the fundamentally limited range of motion in elastic mechanisms can be circumvented to create a frequency doubling functionality analog to angular velocity doubling in classical gears. The proposed mechanism utilizes the elastic deformation of its internal architecture and buckling of microflexures to perform frequency doubling kinematics. We demonstrate this by the fabrication of a microtransmission device for application in mechanical wrist watches. A key benefit of the proposed method is that such a transmission system can be integrated and fabricated as an embedded part of microarchitected materials to boost the frequency characteristics of energy storage, actuators, and inertial sensors to perform adequately for different applications.

Folding is a manufacturing method which can create complex 3D geometries from flat materials and can be particularly useful in cost-sensitive or planar-limited fabrication applications. This paper introduces compliant mechanisms that employ folding techniques from origami to evolve from a flat material to deployed state. We present origami-inspired sacrificial joints, joints which have mobility during assembly of the mechanism but are rigid in their final position, to create regions of high and low stiffness and the proper alignment of compliant flexures in folded mechanisms. To demonstrate the method we fold steel sheet to create some well-known and complex compliant mechanisms.

Vibration energy harvesting can be used as a sustainable power source for various applications. Usually, the generators are designed as devices with a single degree of freedom (SDoF) along the direction of the driving motion. In this research, harvesting from multi-directional (translational) motion sources will be investigated. Three strategies are assessed: a reference SDoF generator, a SDoF generator using an orientation strategy, and a Multi Degree of Freedom (MDoF) system. This led to the development of a design metric by which any 2D design problem can be described by two dimensionless parameters: the relative strength of vibrations, p_v, and the relative dimension of the design space, p_l. It was shown that the relative power density (RPD) of a 2DoF system compared to a reference SDoF system only depends on the product p^∗=p_vp_l, and has a maximum of 1.185 for p^∗=1. The application of powering a hearing aid is investigated as a case study. It was found that the vibrations in the area of the human head while walking can be represented by a two-directional vibration source with p_v=0.55. Three different design spaces are assessed for a miniaturized generator and three different optimal embodiments are found. For one of the considered situations where p^∗=1.1, a 2DoF system was found to have a 16% higher power output compared to a SDoF reference. The aim of future work will be the validation of the developed metric.

Static balancing is used to reduce the actuation stiffness in a translational stage compliant mechanism. The planar and monolithic compliant mechanism is preloaded using a buckling beam of which the top part is guided by a double folded flexure. Hooks, that lock the top part of the beam in place, ensure a permanent static balancing of the entire device. The preloading action is caused by an external shaking or shock to the device. A theoretical micro electromechanical system (MEMS) model with a radius of 18.6 mm is developed and a scale 6:1 prototype is fabricated and tested for static balancing, first eigenfrequency (EF) and eigenmode (EM). Finite element modelling is used to predict static balancing and EM behaviour. Experiments on two equally fabricated prototypes show a reduction of -123 % and -126% actuation stiffness where -104.5% was predicted. The expected reduction for the designed MEMS device is 98.4^%. The experimental first EF of the prototype is 3.10±0.25 Hz against a theoretical value of 3.09 Hz. The theoretical first EF of the MEMS model is 21.8 HZ. The prototypes are successfully preloaded by applying shaking or shock by hand. The predicted minimal energy requirement for this is found to be 4.9e-3 J, while 6.4e-3 J and 5.9e-3 J were calculated based on experimental results. The expected minimal energy required for preloading the designed MEMS device is 1.0e-5 J.

A new fully compliant rotational power transmission mechanism is presented. The design is based on the Pseudo-Rigid-Body Model (PRBM) of the Oldham constant velocity coupling. It can be fabricated as a single piece device with planar materials which make it suitable for micro scale applications. The internal stiffness of the proposed structure is eliminated by static balancing technique. Therefore, the compliance and zero stiffness behavior compensate for the structural error and poor efficiency inherent in rigid-body Oldham coupling, resulting in high mechanical efficiency power transmission system. The device is designed and its motion, torsional stiffness, and torque-angular displacement relations are predicted by the PRBM and finite element modeling. A large/macro scale prototype was manufactured and measured to evaluate the concept. This high efficient power transmission system can be applied in different applications in precision engineering and the relevant field such as micro power transmission system.