Matteo Verotti

MEMS-Based Conjugate Surfaces Flexure Hinge

This paper presents a new concept flexure hinge for MEMS applications and reveals how to design, construct, and experimentally test. This hinge combines a curved beam, as a flexible element, and a pair of conjugate surfaces, whose contact depends on load conditions. The geometry is conceived in such a way that minimum stress conditions are maintained within the flexible beam. A comparison of the new design with the other kind of revolute and flexible joints is presented. Then, the static behavior of the hinge is analyzed by means of a theoretical approach, based on continuum mechanics, and the results are compared to those obtained by means of finite element analysis (FEA) simulation. A silicon hinge prototype is also presented and the construction process, based on single step lithography and reactive ion etching (RIE) technology, is discussed. Finally, a crucial in–SEM experiment is performed and the experimental results are interpreted through the theoretical models.

Development of Micro-Grippers for Tissue and Cell Manipulation with Direct Morphological Comparison

Although tissue and cell manipulation nowadays is a common task in biomedical analysis, there are still many different ways to accomplish it, most of which are still not sufficiently general, inexpensive, accurate, efficient or effective. Several problems arise both for in vivo or in vitro analysis, such as the maximum overall size of the device and the gripper jaws (like in minimally-invasive open biopsy) or very limited manipulating capability, degrees of freedom or dexterity (like in tissues or cell-handling operations). This paper presents a new approach to tissue and cell manipulation, which employs a conceptually new conjugate surfaces flexure hinge (CSFH) silicon MEMS-based technology micro-gripper that solves most of the above-mentioned problems. The article describes all of the phases of the development, including topology conception, structural design, simulation, construction, actuation testing and in vitro observation. The latter phase deals with the assessment of the function capability, which consists of taking a series of in vitro images by optical microscopy. They offer a direct morphological comparison between the gripper and a variety of tissues.

Fabrication of Novel MEMS Microgrippers by Deep Reactive Ion Etching With Metal Hard Mask

The fabrication of a novel class of microgrippers is demonstrated by means of bulk microelectromechanical systems (MEMS) technology using silicon on insulator wafer substrates and deep reactive ion etching. Hard masking is implemented to maximize the selectivity of the bulk etching using sputtered aluminum and aluminum–titanium thin films. The micro-roughness problem related to the use of metal mask is addressed by testing different mask combinations and etching parameters. The O2 flow, SF6 pressure, wafer temperature, and bias power are examined, and the effect of each parameter on micro-masking is assessed. Sidewall damage associated with the use of a metal mask is eliminated by interposing a dielectric layer between silicon substrate and metal mask. Dedicated comb-drive anchors are implemented to etch safely both silicon sides down to the buried oxide, and to preserve the wafer integrity until the final wet release of the completed structures. A first set of complete devices is realized and tested under electrical actuation. [2017-0039]

The development of a MEMS/NEMS-based 3 D.O.F. compliant micro robot

Microrobots are used nowadays in several fields of application, specially in mini invasive surgery. However, they are rather difficult to be constructed, and the traditional micro machining tools are not adequate yet to built the smaller parts. The construction of the microrobots is even harder if more than one D.O.F. are required for the mechanism, because these systems are more complicated. This paper deals with the development of a 3 D.O.F. planar micro platform with remote system of actuation. The new approach of design and manufacturing is based on two innovative solutions: a) the adoption of the technologies used to built MEMS, Micro Electro Mechanical Systems; b) the introduction of new flexural hinge to develop compliant micro mechanisms. The new concept of flexural hinge is described in the paper, also from a theoretical point of view. Several example of possible structures are proposed and analyzed, together with their remote wire actuation systems. Finite Element Analysis (FEA) has been also adopted to analyze the system performance under small deformations. The principle of fabrication is, then, described. The process consists of a sequence of single steps which have allowed to achieved an overall maximum size down to 3–4 mm and the minimum thickness of the smaller components down to 50µm.

New MEMS Tweezers for the Viscoelastic Characterization of Soft Materials at the Microscale

As many studies show, there is a relation between the tissue’s mechanical characteristics and some specific diseases. Knowing this relationship would help early diagnosis or microsurgery. In this paper, a new method for measuring the viscoelastic properties of soft materials at the microscale is proposed. This approach is based on the adoption of a microsystem whose mechanical structure can be reduced to a compliant four bar linkage where the connecting rod is substituted by the tissue sample. A procedure to identify both stiffness and damping coefficients of the tissue is then applied to the developed hardware. Particularly, stiffness is calculated solving the static equations of the mechanism in a desired configuration, while the damping coefficient is inferred from the dynamic equations, which are written under the hypothesis that the sample tissue is excited by a variable compression force characterized by a suitable wave form. The whole procedure is implemented by making use of a control system.

Isotropy in any RR planar dyad under active joint stiffness regulation

The present investigation is dedicated to the study of the static balance at the tip of a planar RR robot. For this case, a configuration can be interpreted, in the static sense, as isotropic when any force applied to the robot wrist yields a small displacement which is theoretically parallel to the applied force (no matter how the force is directed on the plane). This characteristic offers many advantages and is considered as an optimal design goal. Unfortunately, the conditions to achieve such property in RR manipulators are very restrictive, and until now, only one solution is adopted, with a fixed lengths ratio. The present paper reveals how any RR planar robot can achieve isotropy at the tip by using a feedback action at the joints to gain arbitrary elastic coefficients. The new approach of design brings to less restrictive conditions than the previous ones.

Design, optimization and construction of MEMS-based micro grippers for cell manipulation

The need of micromanipulation devices has been growing rapidly during the last decades, specially in the fields of Biology and Micro-Assembly, and many solutions have been proposed to cope with the increasing demand. The present paper suggests a possible way to micromanipulating objects in various conditions, adopting MEMS technologies to develop a microgripper based on a new flexural hinge, recently patented by the Authors. The micromechanism has been modified considering results obtained through FEA. Finally, a brief description of the construction process is provided, together with some experimental activities.

Isotropic Compliance in E(3): Feasibility and Workspace Mapping

A manipulator control system, for which isotropic compliance holds in the Euclidean Space E (3), can be significantly simplified by means of diagonal decoupling. However, such simplification may introduce some limits to the region of the workspace where the sought property can be achieved. The present investigation reveals how to detect which peculiar subset, among four different classes, a given manipulator belongs to. The paper also introduces the concept of control gain ratio for each specific single-input/single-output joint control law in order to limit the maximum gain required to achieve the isotropic compliance condition.

A Comprehensive Evaluation of the Efficiency of an Integrated Biogas, Trigen, PV and Greenhouse Plant, Using Digraph Theory

This paper describes how directed graphs (digraphs) have been used for evaluating the total efficiency of a complex Plant that has been designed for the combined production of food, heat, cooling, and electrical energy. This task required three basic activities. Firstly, the overall plant scheme was studied in detail in order to identify the elementary blocks, each one having its own efficiency value. Each block corresponded to a single node of the digraph. Secondly, the system had to be considered as a whole. The development of the global scheme required the identification of all the directed arcs that were corresponding to the energy flows. Finally, a new algorithm for the evaluation of the overall efficiency was applied to the resultant digraph. This method allowed us to obtain the solution in algebraic symbolic form, automatically, provided that the digraph arc list was supplied to the developed PC code, together with the flow repartitions. The algorithm is quite robust and could also be used in systems with flow recirculation.

Global efficiency of an UPS module integrated with PV, H2, and CAES systems

In this paper the efficiency of a complex plant that serves as Uninterruptible Power Supply (UPS) System for road tunnel service (lighting and air circulation) is evaluated by means of an algorithm which is based on Graph Theory. Such algorithm is able to handle complex systems, even those which have energy circulation, provided that it is possible to identify the power flows, and their corresponding partitions, between the single process stations. The UPS system is composed of systems for energy production and storage, among which a Compressed Air Energy Storage (CAES) plant, Photovoltaic Field (PV), Hydrogen Cells (H2). The new code has been developed in an algebraic manipulation programming environment and so the solution is available either in numerical or in closed-form symbolic expression.