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

Electroactive Artificial Muscles Based on Functionally Antagonistic Core–Shell Polymer Electrolyte Derived from PS-b-PSS Block Copolymer

Electroactive ionic soft actuators, a type of artificial muscles containing a polymer electrolyte membrane sandwiched between two electrodes, have been intensively investigated owing to their potential applications to bioinspired soft robotics, wearable electronics, and active biomedical devices. However, the design and synthesis of an efficient polymer electrolyte suitable for ion migration have been major challenges in developing high-performance ionic soft actuators. Herein, a highly bendable ionic soft actuator based on an unprecedented block copolymer is reported, i.e., polystyrene-b-poly(1-ethyl-3-methylimidazolium-4-styrenesulfonate) (PS-b-PSS-EMIm), with a functionally antagonistic core–shell architecture that is specifically designed as an ionic exchangeable polymer electrolyte. The corresponding actuator shows exceptionally good actuation performance, with a high displacement of 8.22 mm at an ultralow voltage of 0.5 V, a fast rise time of 5 s, and excellent durability over 14 000 cycles. It is envisaged that the development of this high-performance ionic soft actuator could contribute to the progress toward the realization of the aforementioned applications. Furthermore, the procedure described herein can also be applied for developing novel polymer electrolytes related to solid-state lithium batteries and fuel cells

Towards enduring autonomous robots via embodied energy.

Autonomous robots comprise actuation, energy, sensory and control systems built from materials and structures that are not necessarily designed and integrated for multifunctionality. Yet, animals and other organisms that robots strive to emulate contain highly sophisticated and interconnected systems at all organizational levels, which allow multiple functions to be performed simultaneously. Herein, we examine how system integration and multifunctionality in nature inspires a new paradigm for autonomous robots that we call Embodied Energy. Whereas most untethered robots use batteries to store energy and power their operation, recent advancements in energy-storage techniques enable chemical or electrical energy sources to be embodied directly within the structures and materials used to create robots, rather than requiring separate battery packs. This perspective highlights emerging examples of Embodied Energy in the context of developing autonomous robots

Sustainable Robots 4D Printing

Nature frequently serves as an inspiration for modern robotics innovations that emphasize secure human–machine interaction. However, the advantages of increased automation and digital technology integration conflict with the global environmental objectives. Accordingly, biodegradable soft robots have been proposed for a range of intelligent applications. Biodegradability provides soft robotics with an extraordinary functional advantage for operations involving intelligent shape transformation in response to external stimuli such as heat, pH, and light. Soft robot fabrication using conventional manufacturing techniques is inflexible, time-consuming, and labor-intensive. Recent advances in 3D and 4D printing of soft materials and multi-materials have become the key to enabling the direct manufacture of soft robotics with complex designs and functions. This review comprises a detailed survey of 3D and 4D printing advances in biodegradable soft sensors and actuators (BSSA), which serve as the most prominent parts of each robotic system. In addition, a concise overview of biodegradable materials for the fabrication of 3D-printed flexible devices with medical along with industrial applications is provided. A complete summary of current additive manufacturing techniques for BSSA is discussed in depth. Moreover, the concept of biodegradable 4D-printed soft actuators and sensors and biohybrid soft robots is reviewed

Tindiprinditud pehmed täiturid

Väitekirja elektrooniline versioon ei sisalda publikatsiooneTuleviku biomeditsiini- ja robootikarakenduste täiturite jaoks on vaja usaldusväärseid, korratavaid ja skaleeritavaid valmistamismeetodeid. Johannes Gutenbergi näitel võib printimine ka tehislihaste tootmist revolutsioneerida: printimine võimaldab valmistada ühtlase paksuse ja keeruka mustriga täitureid. Selle doktoritöö raames arendati välja prinditud kolmekihilised kahest elektroodist ja neid eraldavast membraanist koosnevad juhtivpolümeeridel põhinevad täiturid. Tänu analoogsele käitumisele looduslike lihastega kutsutakse neid kuju muutvaid materjale ka tehislihasteks ning just selle funktsionaalse sarnasuse põhjal on tõenäolisteks rakendusvaldkondadeks robootika ja meditsiinitehnoloogia. Prinditud mikrotäiturite elektrilisi, mehaanilisi ja täituromadusi saab muuta kolme peamise strateegia abil. Esiteks modifitseeriti selles doktoritöös kommertsiaalse juhtivpolümeertindi koostist, lisades sinna süsinikaerogeeli. Saadud juhtivpolümeer-süsinik-komposiidil põhineval täituril näitas võrreldes ainult juhtivpolümeertäituriga suuremat jõudu. Teiseks varieeriti täituromaduste täppisreguleerimiseks elektroodi paksust, mis oli vähemalt 20 kihi ulatuses lineaarses sõltuvuses kihtide arvust. Paksuse kasvades suurenesid ka täituri jõud, liigutusulatus, pinnajuhtivus ja mahtuvus. Kolmandaks häälestati täituri sooritusvõimet sobivate alus- ehk membraanimaterjalide valikuga. Nitriilbutadieenkautšukile prinditud õhukesel täituril oli lineaarses liigutusrežiimis suurusjärgu võrra suurem liigutusulatus võrreldes tööstusliku polüvinülideendifluoriidmembraaniga täituriga. Selles töös näidati, et piisksadestusprintimise teel on võimalik valmistada pehmeid elektromehaanilisi süsteeme, hoolimata meetodi mõningatest piirangutest. Sobivalt valitud tindimaterjalid ja häälestatud printimisprotsess võimaldavad juba lähitulevikus valmistada pehmeid ja integreeritud elektromehaanilisi süsteeme täielikult printimise teel.Future soft micro actuator applications for biomedical and soft robotic applications need reliable, repeatable, cost-effective and scalable production methods. As an example of Johannes Gutenberg, printing could also revolutionize the production of artificial muscles – printing allows fabrication of homogeneous actuators with intricate patterns. In this thesis technology for fabricating actuators composed of two conducting polymer-based electrodes and a membrane separating them was developed. The actuators change their shape in response to electrical stimuli. Due to this functional similarity to natural muscles, applications in the fields of medicine and robotics are possible. The properties of printed micro actuators are tunable using various strategies. First, the composition of the conducting polymer ink was modified by adding carbon aerogel to the mix. The resulting composite showed superior force compared to pure conducting-polymer actuators. Second, the electrode thickness was controlled to fine-tune the properties. Increasing the thickness also increased the force, strain and capacitance of the actuator and conductivity of the electrodes. Third, the actuator performance was tailored by the selection of various membrane materials. Printing on spin-coated membranes from nitrile butadiene rubber resulted in extremely thin trilayer actuators that had an order of magnitude higher linear strain compared to commercial polyvinylidene based actuators. This work has showed that despite the known limitations of drop-on-demand printing, it is possible to prepare soft electromechanical systems using this technology. With the selection of compatible materials, and by using various strategies to tune the functional properties of the composite towards more preferred outcome it will be possible in the nearest future to realize applications with fully printed and integrated soft electromechanically active component

Nonlinear analysis of a fiber-reinforced tubular conducting polymer-based soft actuator

This study presents the analytical modeling of a fiber-reinforced tubular conducting polymer (FTCP) actuator. The FTCP actuator is a low voltage-driven electroactive polymer arranged in an electrochemical cell. The electrochemical model is developed following an electrical circuit analogy that predicts the charge diffused inside the actuator for an applied voltage. An empirical relation is applied to couple the two internal phenomena, viz., diffusion of the ions and mechanical deformation. Further, the finite deformation theory is applied to predict the blocked force and free strain of the FTCP actuator. The developed model is consistent with existing experimental results for an applied voltage. In addition, the effect of various electrical and geometrical parameters on the performance of the actuator is addressed

Control-based 4D printing: adaptive 4D-printed systems

Building on the recent progress of four-dimensional (4D) printing to produce dynamic structures, this study aimed to bring this technology to the next level by introducing control-based 4D printing to develop adaptive 4D-printed systems with highly versatile multi-disciplinary applications, including medicine, in the form of assisted soft robots, smart textiles as wearable electronics and other industries such as agriculture and microfluidics. This study introduced and analysed adaptive 4D-printed systems with an advanced manufacturing approach for developing stimuli-responsive constructs that organically adapted to environmental dynamic situations and uncertainties as nature does. The adaptive 4D-printed systems incorporated synergic integration of three-dimensional (3D)-printed sensors into 4D-printing and control units, which could be assembled and programmed to transform their shapes based on the assigned tasks and environmental stimuli. This paper demonstrates the adaptivity of these systems via a combination of proprioceptive sensory feedback, modeling and controllers, as well as the challenges and future opportunities they present

Effects of topology optimization in multimaterial 3D bioprinting of soft actuators

Recently, there has been a proliferation of soft robots and actuators that exhibit improved capabilities and adaptability through three-dimensional (3D) bioprinting. Flexibility and shape recovery attributes of stimuli-responsive polymers as the main components in the production of these dynamic structures enable soft manipulations in fragile environments, with potential applications in biomedical and food sectors. Topology optimization (TO), when used in conjunction with 3D bioprinting with optimal design features, offers new capabilities for efficient performance in compliant mechanisms. In this paper, multimaterial TO analysis is used to improve and control the bending performance of a bioprinted soft actuator with electrolytic stimulation. The multimaterial actuator performance is evaluated by the amplitude and rate of bending motion and compared with the single material printed actuator. The results demonstrated the efficacy of multimaterial 3D bioprinting optimization for the rate of actuation and bending

Design, Assembly, and Fabrication of Two-Dimensional Nanomaterials into Functional Biomimetic Device Systems

Diverse functioning biosystems in nature have inspired us and offered unique opportunities in developing novel concepts as well as new class of materials and devices. The design of bioinspired functional materials with tailored properties for actuation, sensing, electronics, and communication has enabled synthetic devices to mimic natural behavior. Among which, artificial muscle and electronic skin that enable to sense and respond to various environmental stimuli in a human-like way have been widely recognized as a significant step toward robotics applications. Polymer materials have previously been dominant in fabricating such functional biomimetic devices owing to their soft nature. However, lacking multifunctionality, handling difficulty, and other setbacks have limited their practical applications. Recently, versatile and high-performance two-dimensional (2D) materials such as graphene and its derivatives have been studied and proven as promising alternatives in this area. In this chapter, we highlight the recent efforts on fabrication and assembly of 2D nanomaterials into functional biomimetic systems. We discuss the structure-function relationships for the development of 2D materials–based biomimetic devices, their tailoring property features, and their variety of applications. We start with a brief introduction of artificial functional biomimetic materials and devices, then summarize some key 2D materials–based systems, including their fabrication, properties, advantages and demonstrations, and finally present concluding remarks and outlook