The convergence of materials science, electronics, and biology, namely bioelectronic interfaces, leads novel and precise communication with biological tissue, particularly with the nervous system. However, the translation of lab‐based innovation toward clinical use calls for further advances in materials, manufacturing and characterization paradigms, and design rules. Herein, a translational framework engineered to accelerate the deployment of microfabricated interfaces for translational research is proposed and applied to the soft neurotechnology called electronic dura mater, e‐dura. Anatomy, implant function, and surgical procedure guide the system design. A high‐yield, silicone‐on‐silicon wafer process is developed to ensure reproducible characteristics of the electrodes. A biomimetic multimodal platform that replicates surgical insertion in an anatomy‐based model applies physiological movement, emulates therapeutic use of the electrodes, and enables advanced validation and rapid optimization in vitro of the implants. Functionality of scaled e‐dura is confirmed in nonhuman primates, where epidural neuromodulation of the spinal cord activates selective groups of muscles in the upper limbs with unmet precision. Performance stability is controlled over 6 weeks in vivo. The synergistic steps of design, fabrication, and biomimetic in vitro validation and in vivo evaluation in translational animal models are of general applicability and answer needs in multiple bioelectronic designs and medical technologies.
The following paper describes a sacrificial layer method for the manufacturing of microfluidic devices in polyimide and SU-8. The technique uses heat-depolymerizable polycarbonates embedded in polyimide or SU-8 for the generation of microchannels and sealed cavities. The volatile decomposition products originating from thermolysis of the sacrificial material escape out of the embedding material by diffusion through the cover layer. The fabrication process was studied experimentally and theoretically with a focus on the decomposition of the sacrificial materials and their diffusion through the polyimide or SU-8 cover layer. It is demonstrated that the sacrificial material removal process is independent of the actual channel geometry and advances linearly with time unlike conventional sacrificial layer techniques. The fabrication method provides a versatile and fast technique for the manufacturing of microfluidic devices for applications in the field of microTAS and Lab-on-a-Chip.
Composite materials offer a combination of properties and a diversity of applications, which cannot be obtained with metals, ceramics or polymers alone. In particular, the insertion of a conductive phase (metallic or inorganic powders or conductive polymers) in an insulating polymer matrix, can result in an enhancement of its electrical conductivity. Various studies have been focused on such electrically conductive polymer composition (ECPCs), which do not have the disadvantages of the pure metal (high density, low chemical resistance, complex manufacturing process). The powder loaded polymer becomes a functional material with specific properties, and can be used for electrical or electromagnetic applications, etc. [1,2] The case of ECPCs based on epoxy resins, are of particular interest to understand the properties of binary composites (morphology, electrical and thermal conductivity), which are obtained in most cases after a heat treatment to crosslink the ECPCs materials. Their main application is conductive adhesives used in the electronic field for connecting and bonding, but it can also be used for manufacturing sensors. [3±5] In this paper we report a new conductive photosensitive composite material, allowing the direct manufacture of electrically conductive micro-components. It is based on a blend containing silver particles embedded in SU-8, an epoxy photopolymer essentially used for the fabrication of high aspect ratio structures by UV-LIGA. SU-8 components are useful for MEMS, fluidic and packaging applications, [6,7] but also as masters for micro-injection-molding (Fig. 1).Nanocomposite characterizations: Formulations containing up to 40 vol.% of silver filler were produced to evaluate the effect of the insertion of silver particles in the photopolymer matrix, both on the photo-polymerization phenomenon and on electrical conductivity of the resulting photo-patterned structures.
Microstereolithography is a technique that allows the manufacture of small and complex three-dimensional (3D) components in plastic material. Many of the components produced by this technique are too small and too complex to be replicated by molding and, consequently, the produced components need to have adequate mechanical or chemical characteristics to be useful. Until now, the choice of materials available in the microstereolithography process was limited to plastic, with only a few photosensitive resins available. In this paper we describe new polymer/composite photosensitive resins that can be used in the microstereolithography process for manufacturing complex 3D components. These resins are based on the insertion of a high load (up to 80 wt%) of alumina nanoparticles in a photosensitive polymer matrix. The resulting composite objects can undergo a debinding and sintering step to be transformed into pure ceramic microcomponents. During this process, their shape is unaltered, but the components undergo some shrinkage. If the load of filler material in the composite resin is high enough, no deformations and no cracks can be seen in the final ceramic components. We present different examples of complex 3D structures in composite material and in pure ceramic.
Cell-derived membrane vesicles that are released in biofluids, like blood or saliva, are emerging as potential non-invasive biomarkers for diseases, such as cancer. Techniques capable of measuring the size and concentration of membrane vesicles directly in biofluids are urgently needed. Fluorescence Single Particle Tracking microscopy has the potential of doing exactly that, by labelling the membrane vesicles with a fluorescent label and analysing their Brownian motion in the biofluid. However, unbound dye in the biofluid can cause high background intensity that strongly biases the fluorescence Single Particle Tracking size and concentration measurements. While such background can be avoided with light sheet illumination, current set-ups require specialty sample holders that are not compatible with high-throughput diagnostics. Here, a microfluidic chip with integrated light sheet illumination is reported, and accurate fluorescence Single Particle Tracking size and concentration measurements of membrane vesicles in cell culture medium and in interstitial fluid collected from primary human breast tumours are demonstrated.3
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