PVDF-based electroactive polymer (EAP) actuators offer large field-induced strains, high compliance, and simple and scalable processing, enabling novel applications in soft robots, wearable devices, and medical devices. This work investigates how blending the poly(vinylidene fluoride−trifluoroethylene−chlorotrifluoroethylene) [P(VDF−TrFE−CTFE)] terpolymer with three phthalate-free plasticizers (butyryl trihexyl citrate (BTHC), 1,2-cyclohexanedicarboxylic acid diisononyl ester (DINCH), and tris(2-ethylhexyl) trimellitate (TOTM)) affects the electromechanical transduction properties. Thin films of plasticizer/terpolymer blends were obtained via stencil printing. Film morphology (SEM), crystallinity (XRD), and mechanical and dielectric properties were investigated at different plasticizer contents, and unimorph actuators were fabricated and characterized to quantify the field-induced transverse strains. The maximum strain increased by 12.5× over the neat terpolymer in TOTM 10 wt % blends, reaching 1% at 33.2 V/μm. The largest tip deflections were achieved with TOTM 5 wt %, giving 246.6 μm at 0.1 Hz and 1.65 mm at resonance (33.7 V/μm). At a fixed field of 18 V/μm, blends with BTHC 15 wt % and TOTM 10 wt % produced 3.8 and 4× strain improvements, while DINCH 5 wt % and TOTM 5 wt % delivered 1.48 and 2.2× higher deflections. DINCH- and TOTM-based actuators withstood at least 60% higher fields than the neat terpolymer, likely due to plasticizer diffusion into the EAP film pores. These results show that the studied plasticizers can enhance transduction in P(VDF−TrFE−CTFE), with further improvements expected by reducing film porosity, establishing optimal annealing processes and plasticizer concentrations.

The Purcell’s swimmer, consisting of three links with two one-degree-of-freedom joints as defined by Edward M. Purcell, has been studied by several authors since its introduction in 1977. Researchers have delved into its mathematical foundations, analysing and optimising its motion for efficient propulsion. However, despite these theoretical advances, the practical realisation and experimental characterisation of Purcell’s swimmers remains relatively unexplored. Critical aspects such as material selection, manufacturing techniques, and experimental validation under real conditions represent important knowledge gaps. This paper contributes to bridging this gap by presenting a prototype of such a swimmer using ionic polymer-metal composites (IPMC) as link actuators. A simulation model is developed based on physical modelling tools in MATLAB^®/Simulink^®. Both simulation and experimental results at low-Reynolds-number ((Formula presented.)) conditions are presented to demonstrate the performance of the swimmer.

The additive manufacturing of electroactive polymer (EAP) devices poses significant challenges due to their distinct structure and dissimilar properties of their constituent materials. It requires deposition of multiple functional materials with different properties, achieving μm-scale resolution in layer thickness, and executing incremental deposition and curing steps while preserving the previously deposited functional material layers. This study introduces an airbrush 3D printer concept and employs it for fabricating EAP transducers. An airbrush 3D printer was constructed by adapting a standard extrusion printer platform and integrating it with a two fluid atomizer (i.e. an airbrush) as the deposition tool. A process was developed for printing of the bending P(VDF-TrFE-CTFE) actuators with carbon black electrodes, and actuators with a single and dual EAP layers were fabricated. The airbrush printer attained in-plane resolution of 0.5mm, thickness resolutions of 0.63 μm and allowed atomizing up to 7% P(VDF-TrFE-CTFE) solutions. The 18 mm × 4 mm EAP actuators achieved 340μm (440 V_pp) and 3.7 mm (400 V_pp, 104 Hz) tip deflections respectively in quasi-static and resonant operation. Airbrush printing therefore proved to be a robust method for printing precursor materials with a wide range of properties, and is anticipated to be a versatile approach for printing other passive and stimuli-responsive materials and devices.

Additive manufacturing of sensors and actuators together with structural materials and electronics will make it possible to fabricate innovative system designs that are overly laborious to realise with conventional methods. While printing of the structural materials and electronics are advancing fast, the additive manufacturing methods for actuators and sensors are in an earlier stage of development. This research will develop a manufacturing process for entirely inkjet printed electroactive polymer (EAP) actuators basing on the P(VDF-TrFE-CTFE) relaxor ferroelectric polymer and Ag electrodes. The process consists of (1) printing an Ag layer on a polyethylene terephthalate (PET) substrate for the bottom electrode; (2) formulating, printing and annealing a P(VDF-TrFE-CTFE) ink for the EAP layer; and (3) printing and sintering an Ag layer on the plasma-treated EAP surface to form the top electrode. Two actuator variations, addressed as DMC and KM512, are manufactured and characterised by their: (a) response to quasi-static excitation (1 Hz sine wave); (b) hysteresis behaviour; (c) actuation amplitude variation with the input voltage; and (d) frequency response. The 18 mm long actuators showed 91.4 µm (DMC, 200 V p p ) and 224 µm (KM512, 275 V p p ) deflections in response to 1 Hz sinusoidal excitation, and 1.10 mm (DMC, 113 Hz, 200 V p p ) and 1.72 mm (KM512, 114 Hz, 200 V p p ) deflections in resonant operation. It is 55% more quasi-static strain and 470% more resonant strain than in earlier fully inkjet-printed polyvinylidene fluoride (PVDF) -based actuators, and comparable to similar partially inkjet-printed actuators. This is the first time that inkjet printing of all three layers of a relaxor ferroelectric actuator have been achieved.

High strains of the relaxor ferroelectric polymers allows to build efficient actuators. While the mechanical impedance of such actuators can be optimized via their morphology, their practical realization requires flexible and versatile fabrication processes. This work devises an efficient procedure for manufacturing unimorph bending actuators basing on the P(VDF-TrFE-CTFE) electroactive polymer (EAP). The fabrication process consists of inkjet printing the Ag electrodes and stencil printing the active P(VDF-TrFE-CTFE) layer. The effect of constituent layer dimensions and properties are analytically modelled to estimate the optimal morphology for highest strains. Actuators are manufactured on polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) substrates and their performance is characterized. On PET substrate, the EAP layer thicknesses of 5 µm up to 24 µm are studied. The PEN-based actuators achieved up to 759 µm deflections in quasi-static (1 Hz, 560 V_pp) and up to 5.95 mm in resonant operation (52 Hz, 550 V_pp). The PET-based actuators achieved up to 486 µm deflections in quasi-static (1 Hz, 980 V_pp) and up to 4.44 mm in resonant operation (116 Hz, 700 V_pp). These results indicate an up to 123% improvement in quasi-static and 60% resonant actuation strains compared to the previously reported similar actuators. Modelling predicts that significantly larger deflections are feasible when fabricating the transducers with optimized morphology.

Dielectric elastomers (DEs) have received significant attention for their good performance among different smart material transducers. This study demonstrates the feasibility of fabricating dielectric elastomer actuators (DEAs) using exclusively inkjet printing technique. The manufactured unimorph bending cantilevers are composed of a polydimethylsiloxane (PDMS) active layer, sandwiched between two compliant electrodes, and printed onto a thin polyimide (PI) substrate. This study addresses the key fabrication challenges associated with inkjet printing such a layered actuator structure. This entails the consistent printing of the Ag electrodes on the smooth PI substrate, a PDMS layer on the Ag electrodes, the Ag electrodes on the smooth PDMS surface, and the respective steps of processing and curing. The fully inkjet-printed DEAs exhibited a maximum tip displacement of 36 µm in quasi-static operation (1 kV_pp) and 12.8 µm in resonant operation (50 Hz, 800 V_pp). This is the first time that inkjet-printing has been employed to print an entire dielectric elastomer actuator, broadening the outlooks to develop innovative devices that base on smart material transducers.

To facilitate smart material transducer research and application, it is important to develop fabrication processes that are widely accessible and compatible with additive manufacturing (AM) techniques. This work addresses inkjet printing and material selection in the fabrication of bending cantilever actuators based on the P(VDF-TrFE-CTFE) relaxor ferroelectric polymer. It investigates the effects of three different substrates (PEN, polyimide and a PET-based) and four different conductive inks (metal- and carbon-based) on the actuator fabrication and performance, to minimize process complexity and need for specialized equipment. First, electrode samples are manufactured for the feasible substrate-ink combination, their sheet resistances are measured, and their feasibility for actuator electrodes is analysed. Then, the simplest viable process is employed to fabricate the actuator samples, and their performance is measured in quasi-static and dynamic experiments. The least complex fabrication process was achieved with the resin-coated PET substrate (IJ-220) and carbon black electrodes (JR-700LV), only requiring a consumer-grade inkjet printer, a spin-coater and a thermal oven. The electrode samples showed 2.29 · 10³ Ω/□ sheet resistance at 10 print repetitions, indicating an actuator’s electrical bandwidth of 9.36 kHz. The manufactured actuators achieved 206 µm tip deflections in response to 1 Hz 300 V excitation, and up to 3 mm deflections in resonant operation at 115 Hz. Therefore, manufacturing flexible designs of well-performing smart material actuators is viable using widely available and low-budget equipment.

Ionic polymer metal composites (IPMCs) are a class of materials with a rising appeal in biological micro-electromechanical systems (bio-MEMS) due to their unique properties (low voltage output, bio-compatibility, affinity with ionic medium). While tailoring and improving actuation capabilities of IPMCs is a key motivator in almost all IPMC manufacturing reports, very little efforts have been dedicated to sensing using IPMC thinner than 100 µm. Most reports on IPMC manufacturing and utilization rely on 180 µm-thick Nafion with platinum electrodes, too stiff for bio-MEMS applications. The same fabrication process on thinner membranes does yield in very poor electrodes and performance, and needs to be studied to increase flexibility and sensitivity in the microscale range. This study demonstrates an electroless Pt deposition method for fabricating bio-MEMS-suitable 50 µm-thick IPMC samples. First, we perform a comparative study on the platinum distribution within the Nafion backbone as well as on the surface for the standard electroless deposition recipe for thin (50 µm) and thick (180 µm) Nafion. We report strong differences in platinum distribution for thick and thin IPMC that experienced the same manufacturing process. By varying chemical concentrations from the standard recipe we obtain convenient platinum distribution on thin Nafion, with platinum mainly localized in proximity of surface, as well as electrodes with lower sheet resistance. We could measure the flexural rigidity as 3.43 × 10 − 8 N·m², 46 times lower than standard 180 µm-thick IPMC. The calculated sensitivity is 0.476 ± 0.02 mV mm⁻¹ and the limit of detection for our sensor is 500 ± 20 µm. This procedure sets a milestone for manufacturing 50 µm-thick IPMC for transducers and sensors in bio-MEMS applications.

Sensing flow rates in structured microenvironments like lab-on-chip (LOC) and organ-on-chip (OoC) is crucial to assess important parameters such as transport of media and molecules of interest. So far, these micro-electromechanical systems for biology (bio-MEMS) mostly rely on flow sensing systems based on thermal sensors. However, thermal flow sensing has limitations, since the measurement principle, which is based on generation of heat, can negatively affect the biological system by increasing the fluid temperature above physiological conditions. To overcome this issue, we propose a novel electro-mechanical flow sensor centered around the deformation of a cantilever made of a thin and biocompatible ionic electroactive polymer. The polymer, called ionic polymer metal composite (IPMC), is doped with ions naturally present in most cell media for LOC and OoC devices. Unlike already existing cantilever-based systems which rely on piezo sensitive materials, our IPMC-based flow sensor shows durability in wet environment. We were able to successfully measure pulsatile flow induced by pipetting with flowrate gradually increasing from 10μL/s to 40μL/s. The proposed flow sensor shows good sensing capabilities (4.78 mV/(μL/s)) with a linear behavior in the studied range. This work sets a milestone for using flexible, electroactive materials for sensing applications in delicate biological microenvironments.

Metamaterials are artificially structured materials and exhibit properties that are uncommon or non-existent in nature. Mechanical metamaterials show exotic mechanical properties, such as negative stiffness, vanishing shear modulus, or negative Poisson's ratio. These properties stem from the geometry and arrangement of the metamaterial unit elements and, therefore, cannot be altered after fabrication. Active mechanical metamaterials aim to overcome this limitation by embedding actuation into the metamaterial unit elements to alter the material properties or mechanical state. This could pave the way for a variety of applications in industries, such as aerospace, robotics, and high-tech engineering. This work proposes and studies an active mechanical metamaterial concept that can actively control the force and deformation distribution within its lattice. Individually controllable actuation units are designed based on piezostack actuators and compliant mechanisms and interconnected into an active metamaterial lattice. Both the actuation units and the metamaterial lattice are modeled, built, and experimentally studied. In experiments, the actuation units attained 240 and 1510 μm extensions, respectively, in quasi-static and resonant operation at 81 Hz, and 0.3 N blocked force at frequencies up to 100 Hz. Quasi-static experiments on the active metamaterial lattice prototype demonstrated morphing into four different configurations: Tilt left, tilt right, convex, and concave profiles. This demonstrated the feasibility of altering the force and deformation distribution within the mechanical metamaterial lattice. Much more research is expected to follow in this field since the actively tuneable mechanical state and properties can enable qualitatively new engineering solutions.

Limitations of conventional actuators and sensors in small-scaled and complex devices have diverted the researches' attentions towards smart material transducers such as ionic polymer-metal composites (IPMCs). In addition to actuation capabilities, IPMCs generate voltage when subjected to mechanical deformation. Utilization of IPMCs as sensors has been studied much less than IPMC actuation, and direct comparison of sensing methods is required for efficient implementation. This paper characterizes IPMC active sensing methods i.e. voltage, current, and charge in terms of frequency responses, coherence, noise, and repeatability. IPMC is excited mechanically between 0.08 Hz and 60 Hz under identical experimental conditions, while signal and displacement are measured. The results provide an absolute comparison for IPMC active sensing dynamic methods, for a typical IPMC (Nafion, Pt, Na⁺).

Microfluidic devices and micro-pumps are increasingly necessitated in many fields ranging from untethered soft robots, to pharmaceutical and biomedical technology. While realization of such devices is limited by miniaturization constraints of conventional actuators, these restrictions can be resolved by using smart material transducers instead. This paper proposes and investigates the first ionic polymer metal composite (IPMC) actuator-driven linear peristaltic pump. With the aim of designing a monolithic device, our concept is based on a single IPMC actuator that is etched on both sides and cut with kirigami-inspired slits by laser ablation. Our pump has a planar configuration, operates with low activation voltages (< 5 V) and is simple to manufacture and thus miniaturize. We build proof-of-principle prototypes of an open and closed design of our proposed pump concept, model the closed design, and evaluate both configurations experimentally. Results show the feasibility of the proposed IPMC-driven pump. Without any optimization, the open pump achieved pumping rates of 669 pL/s, while the closed pump configuration attained a 4.57 Pa pressure buildup and 9.18 nL/s pumping rate. These results indicate feasibility of the concept, and future work will focus on design optimization.