3,383 research outputs found
Design of a bent beam electrothermal actuator for in situ tensile testing of ceramic nanostructures
No full textUltrathin organic membranes: Can they sustain the quest for mechanically robust device applications?
Get PDFSummary: Ultrathin polymeric films have recently attracted tremendous interest as functional components of coatings, separation membranes, and sensors, with applications spanning from environment-related processes to soft robotics and wearable devices. In order to support the development of robust devices with advanced performances, it is necessary to achieve a deep comprehension of the mechanical properties of ultrathin polymeric films, which can be significantly affected by confinement effects at the nanoscale. In this review paper, we collect the most recent advances in the development of ultrathin organic membranes with emphasis on the relationship between their structure and mechanical properties. We provide the reader with a critical overview of the main approaches for the preparation of ultrathin polymeric films, the methodologies for the investigation of their mechanical properties, and models to understand the primary effects that impact their mechanical response, followed by a discussion on the current trends for designing mechanically robust organic membranes
Transient Stiffness Patterning in Hydrogels Driven by Dissipative Mechanochemical Coupling
Get PDFLiving systems adapt to mechanical forces through a series of biochemical feedback loops and dissipative signal transduction mechanisms across multiple length scales. By contrast, synthetic materials are static, closed systems with minimal interaction with their surroundings and lack the ability to adapt to mechanical deformations. Here, a strategy that enables a hydrogel to adapt to mechanical forces through the temporal modulation of its stiffness properties is reported. It is demonstrated that force-induced bond rupture at the disulfide linkages of the hydrogel, coupled with their chemical reoxidation leads to dissipative, transient stiffness functions. The electrochemical generation of the oxidant as the output of a feedback loop triggered by an externally applied force provides high spatiotemporal control over the dissipative process, enabling the engineering of hydrogels with out-of-equilibrium stiffness patterns. Additionally, dose-controlled, spatiotemporal transient release of model protein payloads from the hydrogel is demonstrated. The proposed concept has the potential to enhance the autonomous and interactive functionalities of hydrogels, advancing their applications in the biomedical field and soft robotics
Design and Finite Element Analysis of an Electrothermally Actuated Microgripper for Biomedical Applications
No full textMicromanipulation devices are becoming fundamental tools to study and understand cell biology and cell mechanics. Indeed, to study the individual cell behaviors and interactions, cell samples need to be grasped and moved to testing devices. In recent years, micromanipulators have been demonstrated as an effective means to provide precise sample manipulation. In this paper, a detailed overview of designing and simulation of a biocompatible electro-thermally actuated microgripper with rotary capacitive position sensor is presented. The microgripper is actuated by a chevron-shaped thermal actuator with thin hinges and a rotary capacitive position sensor is integrated with the links of the microgripper in order to sense the microgripper tweezers position. The microgripper herein reported can manipulate biological samples in the size range between 50 μm to 150 μm. Based on the sensitivity calculation of the rotary capacitive position sensors, the sensitivity of the displacement measurement is 102 fF/μm
Design, Analysis, and Simulation of a MEMS Tuning Fork Gyroscope with a Mechanical Amplification Structure
No full textThis paper describes a novel micro-electro-mechanical system (MEMS) tuning fork gyroscope (TFG) design that employs a chevron-shaped displacement mechanism to amplify the displacement generated by the Coriolis force, thereby increasing the TFG’s mechanical sensitivity. This approach was evaluated using both theoretical modeling and finite element analysis (FEA), and the results showed a high degree of agreement between the two methods. A conventional TFG having a comparable area was also designed and analyzed for comparison purposes. By introducing the displacement amplification mechanism, the proposed MEMS TFG design provides an output displacement about 2.5 times higher than the conventional design, according to the computation, without increasing the device footprint. Theoretical analysis and FEA on the TFG with amplification and a conventional TFG confirmed that the amplified displacement significantly improves the mechanical sensitivity of the gyroscope compared to conventional TFG designs
Design and simulation of a MEMS device to investigate the strain engineering properties of 2D nanomaterials
No full textThis paper presents the design and simulation of a novel MEMS device enabling the investigation of the strain engineering properties of 2D materials, like graphene. The novel MEMS device consists of a double set of opposed v-shaped thermal actuators, each provided with heat sink beams, and capacitive readout in order to electrically measure the displacement applied to the nanomaterial sample. The device was designed by means of both analytical modelling and finite element based multiphysics simulations. A displacement capacitive sensor was developed to measure the specimen deformation with high accuracy. The calculated sensitivity is 5.2 fF/nm, and the total stiffness of the device is 40253.6 N/m. The device structure was designed with a compact footprint in order to be compatible with other physical characterization instruments, such as electronic microscopy chambers
Performance Analysis of a CSFH-Based Microgripper: Analytical Modeling and Simulation
No full textMicrogrippers are promising tools for micro-manipulation and characterization of cells. In this paper, a biocompatible electro-thermally actuated microgripper with rotary capacitive position sensor is presented. To overcome the limited displacement possibilities usually provided by electrothermal actuators and to achieve the desired tweezers output displacement, conjugate surface flexure hinges (CSFH) are adopted. The microgripper herein reported can in principle manipulate biological samples in the size range between 15 and 120 µm. A kinematics modeling approach based on the pseudo-rigid-body-method (PRBM) is applied to describe the microgripper’s working mechanism, and analytical modeling, based on finite elements method (FEM), is used to optimize the electrothermal actuator design and the heat dissipation mechanism. Finally, FEM-based simulations are carried out to verify the microgripper, the electrothermal actuator and heat dissipation mechanism performance, and to assess the validity of the analytical modeling
O curso de licenciatura em educação física da Universidade Federal de Santa Catarina: suas concepções de ensino e de educação física
Get PDFDissertação (mestrado) - Universidade Federal de Santa Maria. Centro de Educação Fisica e Desporto
A mechanical system for tensile testing of supported films at the nanoscale
Get PDFStandard tensile tests of materials are usually performed on freestanding specimens. However, such requirement is difficult to implement when the materials of interest are of nanoscopic dimensions due to problems related to their handling and manipulation. In the present paper, a new device is presented for tensile testing of thin nanomaterials, which allows tests to be carried out on specimens initially deposited onto a macroscopic pre-notched substrate. On loading, however, no substrate effects are introduced, allowing the films to be freely stretched. The results obtained from a variety of thin metal or polymeric films are very promising for the further development of this technique as a standard method for nanomaterial mechanical testin
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