This paper presents the fabrication and testing of a new stretchable transducer that can undergo stretching ratio up to 600%without losing its electrical conductivity. The transducer is a functionalized textile fiber exhibiting high elasticity with a Young's modulus of 5.1 Mpa. The transducer under low force application has a gauge factor ranging from 0.24 to 9.17 when stretched between 5% and 100%, respectively, showing a good sensitivity over a wide range of deformation. This is achieved without degradation of the material as shown by the absence of delamination of the conductive layer, even after a 600% stretch. All these properties make this transducer suitable for smart textile applications.

In this letter, we present better understanding and improvements for a neurotoxic gas sensor using liquid crystal (LC) anchoring transition. A theoretical model has been established and checked with dimethyl methylphosphonate gas at concentrations as low as 1 ppm. The experimental results are consistent with the state of the art. A new fabrication technique using jet printing that allows one to increase the transduction dynamic is discussed. Chitosan material has been tested as a functionalization method to increase the lifetime of the transducer.

The development of a piezoresistive thread for characterizing airflow in the vicinity of filters implemented in Heating, Ventilation and Air Conditioning (HVAC) systems is presented. These threads exhibit a sensitive response with a gauge factor of 25 over 10000 cycles of elongation at 5% strain. The thread is then integrated in a laboratory scale ventilation duct to demonstrate that it can discriminate airflow speed between 1 and 3 m.s(-1), which is within the range of interest of HVAC systems.

The design of the electrochromic component of an instrumented contact lens capable of dynamically modifying its color is presented. The device is based on two electrochromic pi-conjugated polymers (CPs) deposited on two electrodes separated by an electrolyte medium. Yellow and cyan electrochromic CPs with two color states are combined to provide a tuneable tint of the eye iris, from green to cyan. The device can switch from green, in which both electrodes are colored, to cyan, in which only the cyan electrode is colored. The additive microsystem process with successive assembling steps allowing the realization of the bichromatic cell in the scleral contact lens is presented, as well as the characterization of the colorimetry and switching dynamics.

Stretchable piezoresistive transducers for strain sensing have been widely developed due to their remarkable sensitivity, elasticity, and cyclability. In this work, commercial elastane yarn (Lycra (R) 1880 dtex) is functionalized by a conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with a dip-coating method. Poly(ethylene glycol) diacrylate (PEGDA) is used as a beneficial additive to improve the affinity between the elastic substrate and the conductive layer. Indicating a small modification of the yarn's mechanical properties, Young's modulus of 3.5 MPa is observed for the transducer. An initial resistance of 3487 Omega is measured for a length of 50 mm. After a training stage involving 100 stretching/releasing cycles to stabilize the electromechanical properties related to morphological structure, the transducer exhibits an average gauge factor of 25 for the interest strain range (0 - 5 %). Furthermore, the cyclability of the yarn is demonstrated by 10,000 deformation cycles with only a slight modification of the relative resistance variation.

A piezoresistive textile fiber is developed for wearable and flow permeable sensing. Our study presents a transducer fabrication method by PEDOT:PSS coating onto a commercial textile fiber Lycra. To improve the bond strength between conducting layer and fiber, before the deposition of PEDOT:PSS at the surface of the fiber, poly(ethylene glycol) diacrylate (PEGDA) is polymerized in-situ into textile to increase the fiber's affinity with the conducting polymer. After 100 stretch/release training cycles for up to 20% strain to stabilize the electromechanical properties, a gauge factor of 60 for a strain between 0 and 5% is obtained.

Although additive manufacturing using multi-photon direct laser writing is nowadays considered as a major tool in the fabrication of future nano/micro-objects and optical components, it is currently limited by the low throughput of the writing process. To circumvent this issue, massive parallelization of the write process is a very promising avenue. However, simultaneous writing of structures in close spatial proximity generates fabrication artefacts, collectively referred to as “proximity effects”, which strongly limit the accessible structure resolution. In this work, we systematically investigate the experimental parameters that influence these effects using specifically designed N×N spot diffractive optical elements. Through computer simulations, we show that these effects can be modeled remarkably successfully simply by taking Point Spread Function overlap and diffusion processes into account. We illustrate the usefulness of the concept by designing a parallel write approach giving access to periodic structures with short inter-object distances while very largely overcoming proximity effects.

Two-photon polymerization is a photochemical process usually initiated by tightly focusing an ultrafast laser pulse into a volume of photosensitive photoresists with a high-numerical-aperture objective. Scanning a write "voxel" in 3D enables near free-form fabrication, but at a limited speed which is a critical factor for industrial purposes, because generally only a single writing-beam is used. Several strategies have been implemented to improve the fabrication speed, one such strategy is massive parallelization which is the approach used in our PHENOmenon H2020 European project. Massive parallelization can be realized by beam splitting diffractive optical elements which allow simultaneous fabrication with thousands of beams, decreasing the overall fabrication time. A major unexpected obstacle is encountered in massively parallelized fabrication: using several spots simultaneously to polymerize, local changes in the 2PP threshold have been observed. We linked this to the proximity effect. The aim of this study is to understand the proximity effect in parallel microfabrication using simulation to predict its behaviour and different systematic experiments to reduce the proximity effect such as changing photoresist, using thinner photoresist layers to increase oxygen penetration or using higher Numerical Aperture Objectives.

In this paper, we present the first realisation and experimentation of a new eye tracking system using an infrared (iR) laser pointer embedded into a wireless smart contact lens. We denote this contact lens prototype as the cyclops lens, in reference to the famous hero of the X-Men comics. The full eye tracker device combines the smart contact lens and its eyewear, which provides a primary source of energy and the beam detection system. We detail the assembling and encapsulation process of the main functionalities into the contact lens and present how a gaze tracking system is achieved, compared to existing conventional eye-tracking ones. Finally, we discuss future technical improvements.

Within the very large range of porous polymers and a related immense scope of applications, we investigate here a specific route to design soft porous polymers with controlled porosity: we use aqueous-based formulations of oligomers with mineral particles which are solidified into a hydrogel upon photo-polymerization; the embedded particles are then chemically etched and the hydrogel is dried to end up with a soft porous polymeric scaffold with micron-scale porosity. Morphological and physical features of the porous polymers are measured and we demonstrate that the porosity of the final material is primarily determined by the amount of initially dispersed sacrificial particles. In addition, the liquid formulations we use to start with are convenient for a variety of material forming techniques such as microfluidics, embossing, etc., which lead to many different morphologies (monoliths, spherical particles, patterned substrates) based on the same initial material.

There is a need for soft actuators in various biomedical applications to manipulate delicate objects such as cells and tissues. Soft actuators are able to adapt to any shape and limit the stress applied to delicate objects. Conjugated polymer (CP) actuators, especially in the so-called trilayer configuration, are interesting candidates for driving such micromanipulators. However, challenges involved in patterning the electrodes in a trilayer with individual contact have prevented further development of soft micromanipulators based on CP actuators. To allow such patterning, two printing-based patterning techniques have been developed. First, an oxidant layer is printed using either syringe-based printing or microcontact printing, followed by vapor-phase polymerization of the CP. Submillimeter patterns with electronic conductivities of 800 S·cm-1 are obtained. Next, laser ablation is used to cleanly cut the final device structures including the printed patterns, resulting in fingers with individually controllable digits and miniaturized hands. The methods presented in this paper will enable integration of patterned electrically active CP layers in many types of complex three-dimensional structures.

A need exists for artificial muscles that are silent, soft, and compliant, with performance characteristics similar to those of skeletal muscle, enabling natural interaction of assistive devices with humans. By combining one of humankind's oldest technologies, textile processing, with electroactive polymers, we demonstrate here the feasibility of wearable, soft artificial muscles made by weaving and knitting, with tunable force and strain. These textile actuators were produced from cellulose yarns assembled into fabrics and coated with conducting polymers using a metal-free deposition. To increase the output force, we assembled yarns in parallel by weaving. The force scaled linearly with the number of yarns in the woven fabric. To amplify the strain, we knitted a stretchable fabric, exhibiting a 53-fold increase in strain. In addition, the textile construction added mechanical stability to the actuators. Textile processing permits scalable and rational production of wearable artificial muscles, and enables novel ways to design assistive devices.

Handling of soft and fragile sub-millimeter sized samples such as cells and tissues requires new tools that allow delicate manipulation. Conducting polymer actuators show unique characteristics suitable to driving such manipulators, however despite their potential, the current fabrication method of the trilayer structures does not allow constructing advanced micromanipulators operating in air using this technology. Here we show a novel bottom-up microfabrication process for conjugated polymer trilayer actuators using various solid polymer electrolytes. In addition, the process design integrates contact pads, which has been an issue for small scale conducting polymer actuators. The microfabrication process starts with a patterned layer of conjugated polymer, followed by depositing a polymer electrolyte and a second patterning of the second conjugated polymer layer. The process resulted in successful fabrication of individually controllable conducting polymer trilayer actuators comprising polyvinylidenefluoride and poly(vinylidenefluoride-co-hexafluoropropylene) membranes and showed good interfacial adhesion between the different layers in the final device. The polyvinylidenefluoride trilayer actuator showed good actuation capability. The developed bottom-up microfabrication method paves the way for the development of novel micromanipulation tools.

Conjugated polymer etching is a key step in the integration of electro-chemical devices into microsystems, and one of the most important challenges for this type of material is to achieve fast etching with commercially available equipment. Conjugated polymer electrochemical devices are promising as they are used in different devices such as OLED, sensors, supercapacitors and actuators. The recent emergence of conducting interpenetrating polymer network actuators (IPN) based on poly(3,4-ethylenedioxythiophene) (PEDOT) has allowed operation frequencies of over 1 kHz to be attained, thus pushing the limits of the conjugated polymer technology. The plasma dry etching step of these PEDOT-based active mechanical devices, with high etching rates of around 2 mu m min(-1), enables the production of these electrochemomechanical devices. To understand the high etching rate of these materials a systematic study of the chemical degradation mechanism of each polymer has been carried on. From the analysis of the etching of all the polymer actuator components, a chemical self-degradation mechanism is proposed to explain the surprisingly high etching rate obtained for PEDOT based materials. Finally, to conclude this study, the usefulness of this fast etching is demonstrated with the operation of standalone micro-beam actuators. (c) 2016 Elsevier B.V. All rights reserved.

We are developing soft, flexible micromanipulators such as micro- tweezers for the handling and manipulation of biological species including cells and surgical tools for minimal invasive surgery. Our aim is to produce tools with minimal dimensions of 100 μm to 1 mm in size, which is 1-2 orders of magnitude smaller than existing technology. However, the displacement of the current developed micromanipulator remains limited due to the low ionic conductivity of the materials. Here, we present developed methods for the fabrication of conjugated polymer trilayer structure which exhibit potential to high stretchability/flexibility as well as a good adhesion between the three different layers. The outcomes of this study contribute to the realisation of low-foot print devices articulated with electroactive polymer actuators for which the physical interface with the power source has been a significant challenge limiting their application. Here, we present a new flexible trilayer structure, which will allow the fabrication of metal-free soft microactuators.

Within the areas of cell biology, biomedicine and minimal invasive surgery, there is a need for soft, flexible and dextrous biocompatible manipulators for handling biological objects, such as single cells and tissues. Present day technologies are based on simple suction using micropipettes for grasping objects. The micropipettes lack the possibility of accurate force control, nor are they soft and compliant and may thus cause damage to the cells or tissue. Other micromanipulators use conventional electric motors however the further miniaturization of electrical motors and their associated gear boxes and/or push/pull wires has reached its limits. Therefore there is an urgent need for new technologies for micromanipulation of soft biological matter. We are developing soft, flexible micromanipulators such as micro- tweezers for the handling and manipulation of biological species including cells and surgical tools for minimal invasive surgery. Our aim is to produce tools with minimal dimensions of 100 μm to 1 mm in size, which is 1-2 orders of magnitude smaller than existing technology. We present newly developed patterning and microfabrication methods for polymer microactuators as well as the latest results to integrate these microactuators into easy to use manipulation tools. The outcomes of this study contribute to the realisation of low-foot print devices articulated with electroactive polymer actuators for which the physical interface with the power source has been a significant challenge limiting their application. Here, we present a new bottom-up microfabrication process. We show for the first time that such a bottom-up fabricated actuator performs a movement in air. This is a significant step towards widening the application areas of the soft microactuators.

A general synthetic strategy for multifunctional actuators is presented, by confining desired functions in separate domains of interpenetrating polymer network materials. Specifically, complementary ionic actuator and shape-memory functions are demonstrated by simultaneous, orthogonal reaction pathways. Synergistic effects also allow dynamic programming and two-way linear shape-memory actuation.