Freeform Fabrication of Ionomeric Polymer-Metal Composite Actuators

Ionomeric polymer-metal composite (IPMC) actuators are a type of soft electromechanically active material which offers large displacement, rapid motion with only ~1V stimulus. IPMC’s are entering commercial applications in toys (Ashley 2003) and biomedical devices (Soltanpour 2001; Shahinpoor 2002; Shahinpoor, Shahinpoor et al. 2003; Soltanpour and Shahinpoor 2003; Soltanpour and Shahinpoor 2004), but unfortunately they can only actuate by bending, limiting their utility. Freeform fabrication offers a possible means of producing IPMC with novel geometry and/or tightly integrated with mechanisms which can yield linear or more complex motion. We have developed materials and processes which allow us to freeform fabricate complete IPMC actuators and their fabrication substrate which will allow integration within other freeform fabricated devices. We have produced simple IPMC’s using our multiple material freeform fabrication system, and have demonstrated operation in air for more than 40 minutes and 256 bidirectional actuation cycles. The output stress scaled to input power is two orders of magnitude inferior to that of the best reported performance for devices produced in the traditional manner, but only slightly inferior to devices produced in a more similar manner. Possible explanations and paths to improvement are presented. Freeform fabrication of complete electroactive polymer actuators in unusual geometries, with tailored actuation behavior, and integrated with other freeform fabricated active components, will enable advances in biomedical device engineering, biologically inspired robotics, and other fields. This work constitutes the first demonstration of complete, functional, IPMC actuators produced entirely by freeform fabrication.Mechanical Engineerin

Materials science and the sensor revolution

For the past decade, we have been investigating strategies to develop ways to provide chemical sensing platforms capable of long-term deployment in remote locations1-3. This key objective has been driven by the emergence of ubiquitous digital communications and the associated potential for widely deployed wireless sensor networks (WSNs). Understandably, in these early days of WSNs, deployments have been based on very reliable sensors, such as thermistors, accelerometers, flow meters, photodetectors, and digital cameras. Biosensors and chemical sensors (bio/chemo-sensors) are largely missing from this rapidly developing field, despite the obvious value offered by an ability to measure molecular targets at multiple locations in real-time. Interestingly, while this paper is focused on the issues with respect to wide area sensing of the environment, the core challenge is essentially the same for long-term implantable bio/chemo-sensors4, i.e.; how to maintain the integrity of the analytical method at a remote, inaccessible location

Dual sensing-actuation artificial muscle based on polypyrrole-carbon nanotube composite

Dual sensing artificial muscles based on conducting polymer are faradaic motors driven by electrochemical reactions, which announce the development of proprioceptive devices. The applicability of different composites has been investigated with the aim to improve the performance. Addition of carbon nanotubes may reduce irreversible reactions. We present the testing of a dual sensing artificial muscle based on a conducting polymer and carbon nanotubes composite. Large bending motions (up to 127 degrees) in aqueous solution and simultaneously sensing abilities of the operation conditions are recorded. The sensing and actuation equations are derived for incorporation into a control system.The research was supported by European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 641822

Integrated static and dynamic modeling of an ionic polymer–metal composite actuator

Ionic polymer–metal composites have been widely used as actuators for robotic systems. In this article, we investigate and verify the characteristics of ionic polymer–metal composite actuators experimentally and theoretically. Two analytical models are utilized to analyze the performance of ionic polymer–metal composites: a linear irreversible electrodynamical model and a dynamic model. We find that the first model accurately predicts the static characteristics of the ionic polymer–metal composite according to the Onsager equations, while the second model is able to reveal the back relaxation characteristics of the ionic polymer–metal composite. We combine the static and dynamic models of the ionic polymer–metal composite and derive the transfer function for the ionic polymer–metal composite’s mechanical response to an electrical signal. A driving signal with a smooth slope and a low frequency is beneficial for the power efficiency

Ioonsete elektroaktiivsete täiturite elektromehaaniline modelleerimine ja juhtimine

Väitekirja elektrooniline versioon ei sisalda publikatsiooneIoonsed elektroaktiivsed polümeerid e. tehislihased on polümeermaterjalid, mille oluline iseärasus on võime muuta elektrienergiat mehhaaniliseks energiaks. Elektroaktiivsetest polümeeridest valmistatud pehmetel täituritel on mitmed huvipakkuvad omadused, näiteks suur deformatsioon madala rakendatud pinge korral, märkimisväärne tekitatud jõu ja massi suhe ning võime töötada nii vesikeskkonnas kui õhus. Niisuguste täiturite kasutamine on paljutõotav eriti just miniatuursetes elusloodusest inspireeritud robootikarakendustes. Näiteks võib tuua aktiivsed mikro-manipulatsioonisüsteemid või isepainduvad pehmed kateetrid, mis on iseäranis nõutud meditsiini-tehnoloogias. Käesoleva väitekirja uurimissfääriks on sellistest materjalidest valmistatud täiturmehhanismide modelleerimine, valmistamine ja juhtimine, päädides sisuliselt ühes tükis valmistatud mitme vabadusastmega paralleelmanipulaatorite väljatöötamisega. Kasutades kompleksset füüsikalistel, elektrokeemilistel ning mehaanilistel alusteadmistel põhinevat mudelit kirjeldatakse ja ennustatakse sellist tüüpi täiturmehhanismide elektrilise sisendi ja mehhaanilise väljundi vahelisi seoseid. Mudel kirjeldab ioonide transpordi dünaamikat elektriväljas, kombineerides Nernst-Plancki ja Poissoni võrrandeid. Mitmekihilise polümeermaterjali mehhaaniline käitumine on seotud laengu- ja massitasakaalu poolt põhjustatud eri kihtide erineva ruumilise paisumisega ja kahanemisega. Kõike seda kokku võttes ning rakendades numbrilist modelleerimist lõplike elementide meetodil saadakse kvantitatiivsed tulemused, mis suudavad prognoosida täiturmehhanismi käitumist ja võimaldavad projekteerida, simuleerida ja optimeerida ka neil täituritel põhinevaid keerulisemaid mehhanisme. Koostatud mudeli valideerimiseks modelleeriti ja valmistati kaks tööpõhimõtteliselt sarnast, kuid erinevatel elektroaktiivsetel polümeermaterjalidel põhinevat ning eri metoodikatel valmistatud mitmest täiturist koosnevat mitme vabadusastmega mikromanipulaatorit. Väitekirjas demonstreeritakse, et koostatud mudel on suure täpsusega võimeline ennustama nii iga individuaalse täituri kui ka mõlema manipulaatori käitumist. Demonstreerimaks piisksadestusprintimismeetodil valmistatud manipulaatori efektiivsust, kirjeldatakse kahte erinevat kontrollrakendust. Esmalt näidatakse tagasisidestamata kontrollitavat seadet, kus pööratakse nelja täituri abil peeglit, suunates laserikiirt X-Y tasapinnas ettemääratud punktidele. Teiseks näidisrakenduseks on tagasisidestatud kontrollmetoodikaga juhitav mikroskoobi preparaadiliigutaja, mille abil saab preparaati nii tõsta-langetada kui ka pöörata. Manipulaatorite valmistamise käigus leiti, et piisksadestusprintimise meetodi täpsus, jõudlus ja skaleeritavus võimaldavad suure tootlikkusega valmistada identseid keerulisi mitmeosalisi manipulaatoreid. See tulemus näitab ilmekalt uue tehnoloogia eeliseid traditsiooniliste valmistamisviiside ees.Ionic electroactive polymers (IEAPs) actuators are kind of smart composite materials that have the ability to convert electrical energy into mechanical energy. The actuators fabricated using IEAP materials will benefit from attractive features such as high compliance, lightweight, large strain, low voltage, biocompatibility, high force to weight ratio, and ability to operate in an aqueous environment as well as in open air. The future of soft robotic actuation system with IEAP actuators is very promising especially in the microdomain for cutting edge applications such as micromanipulation systems, medical devices with higher dexterity, soft catheters with built-in actuation, bio-inspired robotics with better-mimicking properties and active compliant micromechanisms. This dissertation has introduced an effective modelling framework representing the complex electro-chemo-mechanical dynamics that can predict the electromechanical transduction in this kind of actuators. The model describes the ion transport dynamics under electric field by combining the Nernst-Planck and Poisson’s equation and the mechanical response is associated with the volumetric swelling caused by resulting charge and mass balance. The framework of this modelling method to predict the behavior of the actuator enabled to design, simulate and optimize compliant mechanism using IEAP actuators. As a result, a novel parallel manipulator with three degrees of freedom was modelled and fabricated with two different types of electrode materials and is characterized and compared with the simulation model. It is shown that the developed model was able to predict the behavior of the manipulator with a good agreement ensuring the high fidelity of the modelling framework. In the process of the fabrication, it is found that the manipulator fabricated through additive manufacturing method allows to fabricate multipart and intricate patterns with high throughput production capability and also opens the opportunity to print a matrix array of identical actuators over a wide size scale along with improved performance. Finally, to showcase the competence of the printed manipulator two different control application was demonstrated. At first, an open loop four-way optical switch showing the capability of optically triggering four switches in the X-Y plane in an automated sequence is shown followed by closed-loop micromanipulation of an active microscope stage using model predictive control system architecture is shown. The application of the manipulator can be extended to other potential applications such as a zoom lens, a microscope stage, laser steering, autofocusing systems, and micromirror. Overall this dissertation results in modelling, fabrication, and control of ionic electroactive polymer actuators leading to the development of a low cost, monolithic, flat, multi DOF parallel manipulator for micromanipulation application.https://www.ester.ee/record=b524351

Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications

Novel Configurations of Ionic Polymer-Metal Composites (IPMCs) As Sensors, Actuators, and Energy Harvesters

This dissertation starts with describing the IPMC and defining its chemical structure and fundamental characteristics in Chapter 1. The application of these materials in the form of actuator, sensor, and energy harvester are reported through a literature review in Chapter 2. The literature review involves some electromechanical modeling approaches toward physics of the IPMC as well as some of the experimental results and test reports. This chapter also includes a short description of the manufacturing process of the IPMC. Chapter 3 presents the mechanical modeling of IPMC in actuation. For modeling, shear deformation expected not to be significant. Hence, the Euler-Bernoulli beam theory considered to be the approach defining the shape and critical points of the proposed IPMC elements. Description of modeling of IPMC in sensing mode is in Chapter 4. Since the material undergoes large deformation, large beam deformation is considered for both actuation and sensing model. Basic configurations of IPMC as sensor and actuator are introduced in Chapter 5. These basic configurations, based on a systematic approach, generate a large number of possible configurations. Based on the presented mechanisms, some parameters can be defined, but the selection of a proper arrangement remained as an unknown parameter. This mater is addressed by introducing a decision-making algorithm. A series of design for slit cylindrical/tubular/helical IPMC actuators and sensors are introduced in chapter 5. A consideration related to twisting of IPMCs in helical formations is reported through some experiments. Combinations of these IPMC actuators and sensors can be made to make biomimetic robotic devices as some of them are discussed in this chapter and the following Chapters 6 and 7. Another set of IPMC actuator/sensor configurations are introduced as a loop sensor and actuator that are presented subsequently in Chapter 6. These configurations may serve as haptic and tactile feedback sensors, particularly for robotic surgery. Both of these configurations (loop and slit cylindrical) of IPMCs are discussed in details, and some experimental measurements and results are also carried out and reported. The model for different inputs is studied, and report of the feedback is presented. Various designs of these configurations of IPMC are also presented in chapter 7, including their extension to mechanical metamaterials and soft robots

Overview effect of biodiesel storage on properties and characteristics

Abstract. Biofuels based on vegetable oils offer the advantage being a sustainable and environmen-tally attractive alternative to conventional petroleum based fuel. The key issue in using vegetable oil-based fuels is oxidation stability, stoichiometric point, bio-fuel composition, antioxidants on the degradation and much oxygen with comparing to diesel gas oil. This provides a critical review of current understanding of main factor in storage method which affecting the biodiesel properties and characteristics. In the quest for fulfill the industry specifications standard; the fuel should be stored in a clean, dry and dark environment. Water and sediment contamination are basically housekeep-ing issues for biodiesel. Degradation by oxidation yields products that may compromise fuel proper-ties, impair fuel quality and engine performance. The effect of storage method on the fuel properties and burning process in biodiesel fuel combustion will strongly affects the exhaust emissions