Pneumatic Bellow Actuator with Embedded Sensor Using Conductive Carbon Grease.

The present work demonstrates the manufacturing process of a pneumatic bellow actuator with an embedded sensor, utilizing a novel manufacturing approach through the complete use of additive manufacturing techniques, such as direct ink writing (DIW) and traditional fused deposition modeling (FDM) methods. This study is innovative in its integration of a dielectric electroactive polymer (DEAP) structure with sensing electrodes made of conductive carbon grease (CCG), showcasing a unique application of a 3D-printed DEAP with CCG electrodes for combined DEAP sensing and pneumatic actuation. Initial experiments, supported by computational simulations, evaluated the distinct functionality of the DEAP sensor by itself under various pressure conditions. The findings revealed a significant change in capacitance with applied pressure, validating the sensor's performance. After sensor validation, an additive manufacturing process for embedding the DEAP structure into a soft pneumatic actuator was created, exhibiting the system's capability for dual sensing and actuation, as the embedded sensor effectively responded to applied actuation pressure. This dual functionality represents an advancement in soft actuators, especially in applications that require integrated and responsive actuation and sensing capabilities. This work also represents a preliminary step in the development of a 3D-printed dual-modality actuator (pneumatic and electrically activated DEAP) with embedded sensing.

Soft Polymer-Actuated Compliant Microgripper with Adaptive Vibration-Controlled Grasp and Release.

Microgrippers that incorporate soft actuators are appropriate for micromanipulation or microsurgery owing to their ability to grasp objects without causing damage. However, developing a microgripper with a large gripping range that can produce a large force with high speed remains challenging in soft actuation mechanisms. Herein, we introduce a compliant microgripper driven by a soft dielectric elastomer actuator (DEA) called a spiral flexure cone DEA (SFCDEA). The submillimeter-scale SFCDEA exhibited a controllable linear displacement over a high bandwidth and the capability of lifting 100.9 g, which was 670 times higher than its mass. Subsequently, we developed a compliant microgripper based on the SFCDEA using smart composite microstructure technology to fabricate three-dimensional gripper linkages. We demonstrated that the microgripper was able to grasp various millimeter-scale objects with different shapes, sizes, and weights without a complex feedback control owing to its compliance. We proved the versatility of our gripper in robotic manipulation by demonstrating adaptive grasping and releasing of small objects using vibrations owing to its high bandwidth.

Relating Structure to Properties in Non-Conjugated Pendant Electroactive Polymers.

Non-conjugated pendant electroactive polymers (NCPEPs) are an emerging class of polymers that offer the potential of combining the desirable optoelectronic properties of conjugated polymers with the superior synthetic methodologies and stability of traditional non-conjugated polymers. Despite an increasing number of studies focused on NCPEPs, particularly on understanding fundamental structure-property relationships, no attempts have been made to provide an overview on established relationships to date. This review showcases selected reports on NCPEP homopolymers and copolymers that demonstrate how optical, electronic, and physical properties of the polymers are affected by tuning of key structural variables such as the chemical structure of the polymer backbone, molecular weight, tacticity, spacer length, the nature of the pendant group, and in the case of copolymers the ratios between different comonomers and between individual polymer blocks. Correlation of structural features with improved π-stacking and enhanced charge carrier mobility serve as the primary figures of merit in evaluating impact on NCPEP properties. While this review is not intended to serve as a comprehensive summary of all reports on tuning of structural parameters in NCPEPs, it highlights relevant established structure-property relationships that can serve as a guideline for more targeted design of novel NCPEPs in the future.

Enhancement in Capacitance of Ionic Type of EAP-Based Strain Sensors.

This paper aims to enhance the capacitance of electroactive polymer (EAP)-based strain sensors. The enhancement in capacitance was achieved by using a free-standing stretchable polymer film while introducing conducting polymer to fabricate a hybrid dielectric film with controlled conductivity. In this work, styrene-ethylene-butylene-styrene (SEBS) rubber was used as the base material, and dodecyl benzene sulfonate anion (DBSA)-doped polyaniline (PANI) was used as filler to fabricate a hybrid composite conducting film. The maleic anhydride group of the SEBS Rubber and DBSA, the anion of the polyaniline dopant, make a very stable dispersion in Toluene and form a free-standing stretchable film by solution casting. DBSA-doped polyaniline increased the conductivity and dielectric constant of the dielectric film, resulting in a significant enhancement in the capacitance of the EAP-based strain sensor. The sensor presented in this article exhibits capacitance values ranging from 24.7 to 100 µF for strain levels ranging from 0 to 100%, and sensitivity was measured 3 at 100% strain level.

From Nature to Technology: Exploring Bioinspired Polymer Actuators via Electrospinning.

Nature has always been a source of inspiration for the development of novel materials and devices. In particular, polymer actuators that mimic the movements and functions of natural organisms have been of great interest due to their potential applications in various fields, such as biomedical engineering, soft robotics, and energy harvesting. During recent years, the development and actuation performance of electrospun fibrous meshes with the advantages of high permeability, surface area, and easy functional modification, has received extensive attention from researchers. This review covers the recent progress in the state-of-the-art electrospun actuators based on commonly used polymers such as stimuli-sensitive hydrogels, shape-memory polymers (SMPs), and electroactive polymers. The design strategies inspired by nature such as hierarchical systems, layered structures, and responsive interfaces to enhance the performance and functionality of these actuators, including the role of biomimicry to create devices that mimic the behavior of natural organisms, are discussed. Finally, the challenges and future directions in the field, with a focus on the development of more efficient and versatile electrospun polymer actuators which can be used in a wide range of applications, are addressed. The insights gained from this review can contribute to the development of advanced and multifunctional actuators with improved performance and expanded application possibilities.

Influence of Thermal Treatment and Acetic Acid Concentration on the Electroactive Properties of Chitosan/PVA-Based Micro- and Nanofibers.

This study presents, for the first time, a comprehensive investigation of the influence of pre- and post-fabrication parameters for the electroactive properties of electrospun chitosan/PVA-based micro- and nanofibers. Chitosan/PVA fibers were fabricated using electrospinning, characterized, and tested as electroactive materials. Solutions with different acetic acid contents (50, 60, 70, and 80 v/v%) were used, and the rheological properties of the solutions were analyzed. Characterization techniques, such as rheology, conductivity, optical microscopy, a thermogravimetric analysis, differential scanning calorimetry, a tensile test, and FT-IR spectroscopy, were utilized. Fiber mats from the various solutions were thermally treated, and their electroactive behavior was examined under a constant electric potential (10 V) at different pHs (2-13). The results showed that fibers electrospun from 80% acetic acid had a lower electroactive response and dissolved quickly. However, thermal treatment improved the stability and electroactive response of all fiber samples, particularly the ones spun with 80% acetic acid, which exhibited a significant increase in speed displacement from 0 cm-1 (non-thermally treated) to 1.372 cm-1 (thermally treated) at a pH of 3. This study sheds light on the influence of pre- and post-fabrication parameters on the electroactive properties of chitosan/PVA fibers, offering valuable insights for the development of electroactive materials in various applications.

Multiphysics Modeling Framework for Soft PVC Gel Sensors with Experimental Comparisons.

Polyvinyl chloride (PVC) gels have recently been found to exhibit mechanoelectrical transduction or sensing capabilities under compressive loading applications. This phenomenon is not wholly understood but has been characterized as an adsorption-like phenomena under varying amounts and types of plasticizers. A different polymer lattice structure has also been tested, thermoplastic polyurethane, which showed similar sensing characteristics. This study examines mechanical and electrical properties of these gel sensors and proposes a mathematical framework of the underlying mechanisms of mechanoelectrical transduction. COMSOL Multiphysics is used to show solid mechanics characteristics, electrostatic properties, and transport of interstitial plasticizer under compressive loading applications. The solid mechanics takes a continuum mechanics approach and includes a highly compressive Storakers material model for compressive loading applications. The electrostatics and transport properties include charge conservation and a Langmuir adsorption migration model with variable diffusion properties based on plasticizer properties. Results show both plasticizer concentration gradient as well as expected voltage response under varying amounts and types of plasticizers. Experimental work is also completed to show agreeance with the modeling results.

The Use of Collagen Methacrylate in Actuating Polyethylene Glycol Diacrylate-Acrylic Acid Scaffolds for Muscle Regeneration.

After muscle loss or injury, skeletal muscle tissue has the ability to regenerate and return its function. However, large volume defects in skeletal muscle tissue pose a challenge to regenerate due to the absence of regenerative elements such as biophysical and biochemical cues, making the development of new treatments necessary. One potential solution is to utilize electroactive polymers that can change size or shape in response to an external electric field. Poly(ethylene glycol) diacrylate (PEGDA) is one such polymer, which holds great potential as a scaffold for muscle tissue regeneration due to its mechanical properties. In addition, the versatile chemistry of this polymer allows for the conjugation of new functional groups to enhance its electroactive properties and biocompatibility. Herein, we have developed an electroactive copolymer of PEGDA and acrylic acid (AA) in combination with collagen methacrylate (CMA) to promote cell adhesion and proliferation. The electroactive properties of the CMA + PEGDA:AA constructs were investigated through actuation studies. Furthermore, the biological properties of the hydrogel were investigated in a 14-day in vitro study to evaluate myosin light chain (MLC) expression and metabolic activity of C2C12 mouse myoblast cells. The addition of CMA improved some aspects of material bioactivity, such as MLC expression in C2C12 mouse myoblast cells. However, the incorporation of CMA in the PEGDA:AA hydrogels reduced the sample movement when placed under an electric field, possibly due to steric hindrance from the CMA. Further research is needed to optimize the use of CMA in combination with PEGDA:AA as a potential scaffold for skeletal muscle tissue engineering.

Design of Laboratory Stand for Displacement Measurement of IPMC Actuators.

The polymer technology based on Electroactive polymers and metal composite ionic polymer has great potential and advantages in many engineering fields. In this paper, a laboratory stand for testing Ionic polymer-metal composites (IPMC) is presented. The laboratory station includes a power supply system and a measuring system for the displacement of IPMC composites. Tests and measurements are carried out using a laser transducer and a camera equipped with image analysis software to determine the IPMC strips displacement. The experimental investigation of IPMCs under different voltage supplies and waveforms, environmental working humidity conditions, temperature, and loading conditions has proved the significant influence of geometric dimension and the effect of increased stress on the displacement value. For materials powered by a higher voltage value, an increased deflection value was noted. In case of displacement, longer is the sample, higher is the displacement value. The length of the sample under load, affects adversely its performance, resulting in an increase in the load on the sample. For samples of a thick size, a more stable movement with and without load can be noticed.

Engineering Multi-Scale Organization for Biotic and Organic Abiotic Electroactive Systems.

Multi-scale organization of molecular and living components is one of the most critical parameters that regulate charge transport in electroactive systems-whether abiotic, biotic, or hybrid interfaces. In this article, an overview of the current state-of-the-art for controlling molecular order, nanoscale assembly, microstructure domains, and macroscale architectures of electroactive organic interfaces used for biomedical applications is provided. Discussed herein are the leading strategies and challenges to date for engineering the multi-scale organization of electroactive organic materials, including biomolecule-based materials, synthetic conjugated molecules, polymers, and their biohybrid analogs. Importantly, this review provides a unique discussion on how the dependence of conduction phenomena on structural organization is observed for electroactive organic materials, as well as for their living counterparts in electrogenic tissues and biotic-abiotic interfaces. Expansion of fabrication capabilities that enable higher resolution and throughput for the engineering of ordered, patterned, and architecture electroactive systems will significantly impact the future of bioelectronic technologies for medical devices, bioinspired harvesting platforms, and in vitro models of electroactive tissues. In summary, this article presents how ordering at multiple scales is important for modulating transport in both the electroactive organic, abiotic, and living components of bioelectronic systems.

Active and passive drug release by self-assembled lubricin (PRG4) anti-fouling coatings.

Electroactive polymers (EAPs) have been investigated as materials for use in a range of biomedical applications, ranging from cell culture, electrical stimulation of cultured cells as well as controlled delivery of growth factors and drugs. Despite their excellent drug delivery ability, EAPs are susceptible to biofouling thus they often require surface functionalisation with antifouling coatings to limit unwanted non-specific protein adsorption. Here we demonstrate the surface modification of para toluene sulfonate (pTS) doped polypyrrole with the glycoprotein lubricin (LUB) to produce a self-assembled coating that both prevents surface biofouling while also serving as a high-capacity reservoir for cationic drugs which can then be released passively via diffusion or actively via an applied electrical potential. We carried out our investigation in two parts where we initially assessed the antifouling and cationic drug delivery ability of LUB tethered on a gold surface using quartz crystal microbalance with dissipation monitoring (QCM) to monitor molecular interactions occurring on a gold sensor surface. After confirming the ability of tethered LUB nano brush layers on a gold surface, we introduced an electrochemically grown EAP layer to act as the immobilisation surface for LUB before subsequently introducing the cationic drug doxorubicin hydrochloride (DOX). The release of cationic drug was then investigated under passive and electrochemically stimulated conditions. High-performance liquid chromatography (HPLC) was then carried out to quantify the amount of DOX released. It was shown that the amount of DOX released from nano brush layers of LUB tethered on gold and EAP surfaces could be increased by up to 30% per minute by applying a positive electrochemically stimulating pulse at 0.8 V for one minute. Using bovine serum albumin (BSA), we show that DOX loaded LUB tethered on para toluene sulfonic acid (pTS) doped polypyrrole retained antifouling ability of up to 75% when compared to unloaded tethered LUB. This work demonstrates the unique, novel ability of tethered LUB to actively participate in the delivery of cationic therapeutics on different substrate surfaces. This study could lead to the development of versatile multifunctional biomaterials for use in wide range of biomedical applications, such as dual drug delivery and lubricating coatings, dual drug delivery and antifouling coatings, cellular recording and stimulation.

Spectroelectrochemistry of Electroactive Polymer Composite Materials.

In this review, we have summarized the main advantages of the method of spectroelectrochemistry as applied to recent studies on electrosynthesis and redox processes of electroactive polymer composite materials, which have found wide application in designing organic optoelectronic devices, batteries and sensors. These polymer composites include electroactive polymer complexes with large unmovable dopant anions such as polymer electrolytes, organic dyes, cyclodextrins, poly(ß-hydroxyethers), as well as polymer-inorganic nanocomposites. The spectroelectrochemical methods reviewed include in situ electron absorption, Raman, infrared and electron spin resonance spectroscopies.

Electroactive Polymer-Based Composites for Artificial Muscle-like Actuators: A Review.

Unlike traditional actuators, such as piezoelectric ceramic or metallic actuators, polymer actuators are currently attracting more interest in biomedicine due to their unique properties, such as light weight, easy processing, biodegradability, fast response, large active strains, and good mechanical properties. They can be actuated under external stimuli, such as chemical (pH changes), electric, humidity, light, temperature, and magnetic field. Electroactive polymers (EAPs), called 'artificial muscles', can be activated by an electric stimulus, and fixed into a temporary shape. Restoring their permanent shape after the release of an electrical field, electroactive polymer is considered the most attractive actuator type because of its high suitability for prosthetics and soft robotics applications. However, robust control, modeling non-linear behavior, and scalable fabrication are considered the most critical challenges for applying the soft robotic systems in real conditions. Researchers from around the world investigate the scientific and engineering foundations of polymer actuators, especially the principles of their work, for the purpose of a better control of their capability and durability. The activation method of actuators and the realization of required mechanical properties are the main restrictions on using actuators in real applications. The latest highlights, operating principles, perspectives, and challenges of electroactive materials (EAPs) such as dielectric EAPs, ferroelectric polymers, electrostrictive graft elastomers, liquid crystal elastomers, ionic gels, and ionic polymer-metal composites are reviewed in this article.

Soft Actuators Based On Carbon Nanomaterials.

Inspired by the sophisticated design of biological systems, interest in soft intelligent actuators has increased significantly in recent years, providing attractive strategies for the design of elaborate soft mechanical systems. For the construction of those soft actuators, carbon nanomaterials were extensively and successfully explored for the properties of highly conductive, electrothermal, and photothermal conversion. This review aims to trace the recent achievements for the material and structural design as well as the general mechanisms of the soft actuators, paying particular attention to the contribution of carbon nanomaterials resulted from their diversified interplaying properties, which realized the flexible and dexterous deformation responding to various environmental stimuli, including light, electricity and humidity. The properties and mechanisms of soft actuators are summarized and the potential for future applications and research are presented.

Synthesis and Excimer Formation Properties of Electroactive Polyamides Incorporated with 4,5-Diphenoxypyrene Units.

A new dietherpyrene-cored diamine monomer, namely, 4,5-bis(4-aminophenoxy)pyrene, was successful synthesized and formed a series of electroactive polyamides with an aryloxy linkage in a polymer main chain and bearing pyrene chromophore as a pendent group using conventional one-pot polycondensation reactions with commercial aromatic/aliphatic dicarboxylic acids. The resulting polyamides exhibited good solubility in polar organic solvents and, further, can be made into transparent films. They had appropriate levels of thermal stability with moderately high glass-transition values. The dilute NMP solutions of these polyamides exhibited pyrene characteristic fluorescence and also showed a remarkable additional excimer emission peak centered at 475 nm. Electrochemical studies of these polymer films showed that these polyamides have both p- and n-dopable states as a result of the formation of radical cations and anions of the electroactive pyrene moieties.

Exploring electroactive microenvironments in polymer-based nanocomposites to sensitize bacterial cells to low-dose embedded silver nanoparticles.

The search for alternative antimicrobial strategies capable of avoiding resistance mechanisms in bacteria are highly needed due to the alarming emergence of antimicrobial resistance. The application of physical stimuli as a mean of sensitizing bacteria for the action of antimicrobials on otherwise resistant bacteria or by allowing the action of low quantity of antimicrobials may be seen as a breakthrough for such purpose. This work proposes the development of antibacterial nanocomposites using the synergy between the electrically active microenvironments, created by a piezoelectric polymer (poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE)), with green-synthesized silver nanoparticles (AgNPs). The electrical microenvironment is generated via mechanical stimulation of piezoelectric PVDF-TrFE/AgNPs films using a lab-made mechanical bioreactor. The generated material's electrical response further translates to bacterial cells, namely Escherichia coli and Staphylococcus epidermidis which in combination with AgNPs and the specific morphological features of the material induce important antibacterial and antibiofilm activity. Both porous and non-porous PVDF composites have shown antibacterial characteristics when stimulated at a mechanical frequency of 4 Hz being the effect boosted when AgNPs were incorporated in the nanocomposite, reducing in more than 80% the S. epidermidis bacterial growth in planktonic and biofilm form. The electroactive environments sensitize the bacteria allowing the action of a low dose of AgNPs (1.69% (w/w)). Importantly, the material did not compromise the viability of mammalian cells, thus being considered biocompatible. The piezoelectric stimulation of PVDF-based polymeric films may represent a breakthrough in the development of antibacterial coatings for devices used at hospital setting, taking advantage on the use of mechanical stimuli (pressure/touch) to exert antibacterial and antibiofilm activity. STATEMENT OF SIGNIFICANCE: The application of physical methods in alternative to the common chemical ones is seen as a breakthrough for avoiding the emergence of antimicrobial resistance. Antimicrobial strategies that take advantage on the capability of bacteria to sense physical stimuli such as mechanical and electrical cues are scarce. Electroactive nanocomposites comprised of poly(vinylidene fluoride-co-trifluoroethylene (PVDF-TrFE) and green-synthesized silver nanoparticles (AgNPs) were developed to obtain material able to inhibit the colonization of microorganisms. By applying a mechanical stimuli to the nanocomposite, which ultimately mimics movements such as walking or touching, an antimicrobial effect is obtained, resulting from the synergy between the electroactive microenvironments created on the surface of the material and the AgNPs. Such environments sensitize the bacteria to low doses of antimicrobials.

A DIY Fabrication Approach of Stretchable Sensors Using Carbon Nano Tube Powder for Wearable Device.

Soft robotics and wearable devices are promising technologies due to their flexibility. As human-soft robot interaction technologies advance, the interest in stretchable sensor devices has increased. Currently, the main challenge in developing stretchable sensors is preparing high-quality sensors via a simple and cost-effective method. This study introduces the do-it-yourself (DIY)-approach to fabricate a carbon nanotube (CNT) powder-based stretchable sensor. The fabrication strategy utilizes an automatic brushing machine to pattern CNT powder on the elastomer. The elastomer ingredients are optimized to increase the elastomer compatibility with the brushing method. We found that polydimethylsiloxane-polyethyleneimine (PDMS-PEIE) is 50% more stretchable and 63% stickier than previously reported PDMS 30-1. With these improved elastomer characteristics, PDMS-PEIE/multiwalled CNT (PDMS-PEIE/MWCNT-1) strain sensor can realize a gauge factor of 6.2-8.2 and a responsivity up to 25 ms. To enhance the compatibility of the powder-based stretchable sensor for a wearable device, the sensor is laminated using a thin Ecoflex membrane. Additionally, system integration of the stretchable sensors are demonstrated by embedding it into a cotton-glove and a microcontroller to control a virtual hand. This cost-effective DIY-approach are expected to greatly contribute to the development of wearable devices since the technology is simple, economical, and reliable.

In situ growth of electroactive polymers via ATRP to construct a biosensing interface for tumor marker.

A novel biosensing interface for tumor markers was designed based on the atom transfer radical polymerization (ATRP) of poly(isopropenylphenol) (PPPL) in situ initiated by the fixing of p-chloromethyl benzoic acid on the surface of amino-modified electrodes. It was found that the electrochemical activity of PPPL itself can provide sufficient signals for these biosensors, which can avoid signal leakage and streamline the interface modification process. Cu(II) ions absorbed on the carbon spheres and then were released via acid stimulation to act as a catalyst to participate in the interface polymerization with ATRP. As the concentration of targets increased, more Cu(II) ions were released, and the electrochemical signal of polymers was enhanced. Therefore, the sensitive detection of carbohydrate antigen 19-9 (CA19-9) as a model target was achieved, with an ultralow limit of detection of 39 µU mL-1 and wide detection range from 100 µU mL-1 to 100 U mL-1 under optimal conditions. Furthermore, this method achieved satisfying performance in human blood serum with good inter-assay precision (RSD < 6%) and satisfactory recovery of ~ 99-105%. According to the results, this work is of great significance for constructing biosensor interfaces via in situ polymerization. A novel biosensing interface for tumor marker was designed based on atom transfer radical polymerization (ATRP), which poly(isopropenylphenol) with electrochemical signal was fabricated in situ on electrode.

Clinical Potential of Nerve Input to Tumors: A Bioelectricity Perspective.

We support the notion that the neural connections of the tumor microenvironment (TME) and the associated 'bioelectricity' play significant role in the pathophysiology of cancer. In several cancers, the nerve input promotes the cancer process. While straightforward surgical denervation of tumors, therefore, could improve prognosis, resulting side effects of such a procedure would be unpredictable and irreversible. On the other hand, tumor innervation can be manipulated effectively for therapeutic purposes by alternative novel approaches broadly termed "electroceuticals." In this perspective, we evaluate the clinical potential of targeting the TME first through manipulation of the nerve input itself and second by application of electric fields directly to the tumor. The former encompasses several different biophysical and biochemical approaches. These include implantable devices, nanoparticles, and electroactive polymers, as well as optogenetics and chemogenetics. As regard bioelectrical manipulation of the tumor itself, the "tumor-treating field" technique, applied to gliomas commonly in combination with chemotherapy, is evaluated. Also, as electroceuticals, drugs acting on ion channels and neurotransmitter receptors are highlighted for completeness. It is concluded, first, that electroceuticals comprise a broad range of biomedical tools. Second, such electroceuticals present significant clinical potential for exploiting the neural component of the TME as a strategy against cancer. Finally, the inherent bioelectric characteristics of tumors themselves are also amenable to complementary approaches. Collectively, these represent an evolving, dynamic field and further progress and applications can be expected to follow both conceptually and technically.