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There is an increasing interest in atomic layer deposition (ALD) on polymers for the development of membranes, electronics, (3D) nanostructures and specially for the development of hermetic packaging of the new generation of flexible implantable micro-devices. This evolution demands a better understanding of the ALD nucleation process on polymers, which has not been reported in a visual way. Herein, a visual study of ALD nucleation on polymers is presented, based on the different dry etching speeds between polymers (fast) and metal oxides (slow). An etching process removes the polyimide with the nucleating ALD acting as a mask, making the nucleation features visible through secondary electron microscopy analyses. The nucleation of both Al2O3 and HfO2 on polyimide was investigated. Both materials followed an island-coalescence nucleation. First, local islands formed, progressively coalescing into filaments, which connected and formed meshes. These meshes evolved into porous layers that eventually grew to a full layer, marking the end of the nucleation. Cross-sections were analyzed, observing no sub-surface growth. This approach was used to evaluate the influence of plasma-activating polyimide on the nucleation. Plasma-induced oxygen functionalities provided additional surface reactive sites for the ALD precursors to adsorb and start the nucleation. The presented nucleation study proved to be a straightforward and simple way to evaluate ALD nucleation on polymers.

Barrier layers for the long-term encapsulation of implantable medical devices play a crucial role in the devices&rsquo, performance and reliability. Typically, to understand the stability and predict the lifetime of barriers (therefore, the implantable devices), the device is subjected to accelerated testing at higher temperatures compared to its service parameters. Nevertheless, at high temperatures, reaction and degradation mechanisms might be different, resulting in false accelerated test results. In this study, the maximum valid temperatures for the accelerated testing of two barrier layers were investigated: atomic layer deposited (ALD) Al2O3 and stacked ALD HfO2/Al2O3/HfO2, hereinafter referred to as ALD-3. The in-house developed standard barrier performance test is based on continuous electrical resistance monitoring and microscopic inspection of Cu patterns covered with the barrier and immersed in phosphate buffered saline (PBS) at temperatures up to 95 &deg, C. The results demonstrate the valid temperature window to perform temperature acceleration tests. In addition, the optimized ALD layer in combination with polyimide (polyimide/ALD-3/polyimide) works as effective barrier at 60 &deg, C for 1215 days, suggesting the potential applicability to the encapsulation of long-term implants.

Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging of implantable medical devices, however realizing these devices with long-term hermeticity up to several years remains a great challenge. Here, polyimide (PI) based hermetic encapsulation was greatly improved by atomic layer deposition (ALD) of a nanoscale-thin, biocompatible sandwich stack of HfO2/Al2O3/HfO2 (ALD-3) between two polyimide layers. A thin copper film covered with a PI/ALD-3/PI barrier maintained excellent electrochemical performance over 1028 days (2.8 years) during acceleration tests at 60 &deg, C in phosphate buffered saline solution (PBS). This stability is equivalent to approximately 14 years at 37 &deg, C. The coatings were monitored in situ through electrochemical impedance spectroscopy (EIS), were inspected by microscope, and were further analyzed using equivalent circuit modeling. The failure mode of ALD Al2O3, ALD-3, and PI soaking in PBS is discussed. Encapsulation using ultrathin ALD-3 combined with PI for the packaging of implantable medical devices is robust at the acceleration temperature condition for more than 2.8 years, showing that it has great potential as reliable packaging for long-term implantable devices.

Varying physico-chemical properties of synthetic hydrogels and introducing additives can induce a cell interactive response of hydrogels. Hydrogels were developed based on acrylate-endcapped urethane-based poly(ethylene glycol) precursors with varying backbone molecular weight (2000–8000 g/mol), in combination with the nanoclay Laponite to explore effects on swelling, mechanical and in vitro biological properties. The combined effect of molecular weight and Laponite concentration enables the development of hybrid materials useful for different biomedical applications. Gel fractions approximating 100% along with tunable swelling (4–11 g/g polymer) and mechanical properties (Young's Modulus 0.1–0.6 MPa) are obtained. All materials are non-cytotoxic and AUPs without Laponite are non cell-interative rendering them suitable for non-adherent biomedical applications. Hydrogels composed of Laponite (0.5 or 1 wt%) and PEG backbone molecular weight of 2000 g/mol promote cell proliferation useful to function as synthetic dermal matrices or scaffolds for tissue engineering applications.

Hydrogel biomaterials can be easily enriched with bioactive substances such as the mineralization-promoting enzyme alkaline phosphatase (ALP). In this study, poly(vinyl alcohol) (PVA) hydrogels designed for osteochondral regeneration containing incorporated ALP were mineralized with calcium phosphate (CaP) and magnesium phosphate (MgP) by incubation in solutions of 0.1 M calcium or magnesium glycerophosphate (CaGP, MgGP). Hydrogels incubated in water served as controls. More mineral was formed in hydrogels incubated in CaGP than in MgGP. Rheometry revealed that mechanical strength (storage modulus) decreased in the order: CaGP>MgGP>water. Physicochemical charaterization showed that hydrogels incubated in CaGP appeared to be mineralized with apatite and amorphous CaP, while hydrogels incubated in MgGP appeared to be mineralized with plate-like MgP crystals and amorphous MgP. Hydrogels incubated in water were devoid of mineralization. Cell viability testing showed that proliferation on hydrogels incubated in MgGP was comparable to that on non-mineralized samples and superior to that on hydrogels incubated in CaGP. The results prove the principle of enzymatic mineralization of PVA hydrogels with CaP and MgP. Further work may concentrate on in vivo evaluation of the suitability of these mineralized hydrogels for bone or osteochondral regeneration applications.

Mineralization of hydrogels, desirable for bone regeneration applications, may be achieved enzymatically by incorporation of alkaline phosphatase (ALP). ALP-loaded gellan gum (GG) hydrogels were mineralized by incubation in mineralization media containing calcium and/or magnesium glycerophosphate (CaGP, MgGP). Mineralization media with CaGP:MgGP concentrations 0.1:0, 0.075:0.025, 0.05:0.05, 0.025:0.075 and 0:0.1 (all values mol/dm3, denoted A, B, C, D and E, respectively) were compared. Mineral formation was confirmed by IR and Raman, SEM, ICP-OES, XRD, TEM, SAED, TGA and increases in the the mass fraction of the hydrogel not consisting of water. Ca was incorporated into mineral to a greater extent than Mg in samples mineralized in media A–D. Mg content and amorphicity of mineral formed increased in the order A B > C > D, but were significantly higher for samples mineralized in medium E. The attachment and vitality of osteoblastic MC3T3-E1 cells were higher on samples mineralized in media B–E (containing Mg) than in those mineralized in medium A (not containing Mg). All samples underwent degradation and supported the adhesion of RAW 264.7 monocytic cells, and samples mineralized in media A and B supported osteoclast-like cell formation. Copyright © 2014 John Wiley & Sons, Ltd.

Mineralization of hydrogels is desirable prior to applications in bone regeneration. CaCO3 is a widely used bone regeneration material, and Mg, when used as a component of calcium phosphate biomaterials, has promoted bone-forming cell adhesion and proliferation and bone regeneration. In this study, gellan gum hydrogels were mineralized with carbonates containing different amounts of calcium (Ca) and magnesium (Mg) by alternate soaking in, firstly, a calcium and/or magnesium ion solution and, secondly, a carbonate ion solution. This alternate soaking cycle was repeated five times. Five different calcium and/or magnesium ion solutions, containing different molar ratios of Ca to Mg ranging from Mg free to Ca free were compared. Carbonate mineral formed in all sample groups subjected to the alternate soaking cycle. Ca : Mg elemental ratio in the mineral formed was higher than in the respective mineralizing solution. Mineral formed in the absence of Mg was predominantly CaCO3 in the form of a mixture of calcite and vaterite. Increasing the Mg content in the mineral formed led to the formation of magnesian calcite and decreased the total amount of the mineral formed and its crystallinity. Hydrogel mineralization and increasing Mg content in mineral formed did not obviously improve proliferation of MC3T3-E1 osteoblast-like cells or differentiation after 7 days.

Despite its widespread application in the fields of ophthalmology, orthopedics and dentistry and the stringent need for polymer packagings that induce in vivo tissue integration, the full potential of poly(methyl methacrylate) (PMMA) and its derivatives as medical device packaging material has not been explored yet. We therefore elaborated on the development of a universal coating for methacrylate-based materials which ideally should reveal cell-interactivity irrespective of the polymer substrate bulk properties. Within this perspective, the present work reports on the UV-induced synthesis of PMMA and its more flexible poly(ethyleneglycol) (PEG)-based derivative (PMMAPEG) and its subsequent surface decoration using polydopamine (PDA) as well as PDA combined with gelatin B (Gel B). Successful application of both layers was confirmed by multiple surface characterization techniques. The cell interactivity of the materials was studied by performing live-dead assays and immunostainings of the cytoskeletal components of fibroblasts. It can be concluded that only the combination of PDA and Gel B yields materials posessing similar cell interactivities, irrespective of the physicochemical properties of the underlying substrate. The proposed coating outperforms both the PDA functionalized and the pristine polymer surfaces. A universal cell-interactive coating for methacrylate-based medical device packaging materials has thus been realized.

© 2015 Elsevier B.V. All rights reserved. Cracks are concrete's worst problem. External, passive treatments are expensive and time consuming. pH-responsive superabsorbent polymers (SAPs) offer an internal active solution. When cracks occur, the SAPs can swell, fill the crack (self-sealing) and assist in the formation of healing products (self-healing). In previous work, a range of (superabsorbent) polymers have been synthesized and characterized. Based on these results, the two best performing SAPs were chosen for further characterization. The results indicate that the SAPs developed do not show degradation in cement filtrate solutions. Upon addition of SAPs, a decrease in mortar strength occurred, yet a positive effect on self-sealing was observed since the water permeability decreased. Furthermore, the formation of products became apparent at the sealed cracks of the mortar samples containing 1 m% SAPs. Identification using scanning electron microscopy, infrared spectroscopy and thermogravimetric analysis indicated that the products mainly consisted of healing products (more specifically CaCO3) which is illustrative for self-healing. ispartof: REACTIVE & FUNCTIONAL POLYMERS vol:93 pages:68-76 status: published

Introduction: Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration[1],[2]. Hydrogels have been most commonly mineralized with calcium phosphate (CaP), but hydrogel-CaCO3 composites have received less attention. Magnesium (Mg) has been added to CaP to stimulate cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate-based biomaterials remains uninvestigated. In this study, gellan gum (GG) hydrogels were mineralized enzymatically with (CaCO3), Mg-enriched CaCO3 and magnesium carbonate to generate composite biomaterials for bone regeneration. GG is an inexpensive, biotechnologically produced anionic polysaccharide, from which hydrogels for cartilage regeneration have been formed by crosslinking with divalent ions[3].Methods: GG hydrogels were loaded with the enzyme urease by incubation in 5% (w/v) urease solution and mineralized for 5 days in five different media denoted as UA, UB, UC, UD and UE, which contained urea (0.17 M) and different concentrations of CaCl2 and MgCl2 (270:0, 202.5:67.5, 135:135, 67.5:202.5 and 0:250, respectively (mmol dm-3)). Discs were autoclaved and subjected to physiochemical, mechanical and cell biological characterization.Results: FTIR, SEM, TGA and XRD analysis revealed that increasing magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite formed at high magnesium concentration in the absence of calcium. Amount of mineral formed and compressive strength decreased with increasing magnesium concentration in the mineralization medium. ICP analysis revealed that Ca:Mg elemental ratio in the mineral formed was higher than in the respective mineralization media. Mineralization of hydrogels promoted adhesion and growth of osteoblast-like cells, which were supported best on mineralized hydrogels containing no or little magnesium. Hydrogels mineralized with hydromagnesite displayed higher cytotoxicity.Discussion: Enzymatic mineralization of GG hydrogels with CaCO3 in the form of calcite successfully reinforced hydrogels and promoted osteoblast-like cell adhesion and growth, but Mg enrichment had no positive effect. This is in contrast with other studies reporting that incorporation of Mg into GG mineralized with CaP promotes cell adhesion and proliferation[4]. Conclusion: Sample groups UA and UB seem to be the most promising due to the superior amount of mineral formed and cell adhesion and proliferation.

A ruthenium based benzylidene complex bearing an O,N-bidentate Schiff base ligand exhibits poor olefin metathesis activity but generates a highly active catalyst system when treated with acidic cocatalysts. Various Lewis acids were able to boost the ring opening metathesis polymerization (ROMP) of cycloocta-1,5-diene (COD). The best results were obtained with trichlorosilane (HSiCl3), which was also found to improve metathesis activity of the Grubbs second generation catalyst [RuCl2( CHPh)(H2IMes)(PCy3)] in the ROMP of COD and the ring closing metathesis (RCM) of diethyl diallylmalonate.

This study describes the qualitative analysis of the polymerization reaction of DCPD (DiCycloPentaDiene) and its reaction products. The polymerization was carried out using WCl6/Si(allyl)4 (1), first generation Grubbs’ (2) and second generation Grubbs’ (3) catalysts. When system 1 was used as a catalyst, solution concentration determined whether soluble or insoluble polymer was obtained. When Grubbs’ catalysts were employed, insoluble polymer was formed in all cases. The ring opening metathesis polymerization (ROMP)-reaction and the resulting polymers were monitored in situ via FT-Raman-spectroscopy. Using FT-Raman-spectroscopy, the stereospecific nature of the forming polymer can be determined during the polymerization reaction. The obtained spectra illustrate that the linear polymer has a prevailing cis double bond configuration, while the polymer formed using the 1e generation Grubbs catalyst has a predominant trans double bond configuration. The second generation Grubbs catalyst exhibits a poor stereoselectivity. These results are in accordance to literature data where the stereospecific nature of these polymers where determined using NMR-spectroscopy.

This paper describes the influence of polydopamine and polyamine surface modifications of an etched epoxy cresol novolak (ECN) resin on the initial electroless copper deposition. Three different strategies to introduce polyamines on a surface in aqueous environment are applied: via polyethyleneimine adsorption (PEI), via polydopamine and via polyamines grafted to polydopamine. Next, the influence of these surface modifications on the catalytic palladium activation is investigated through X-ray photoelectron spectroscopy (XPS) analysis. Finally, the initial electroless copper deposition on modified epoxy surfaces is evaluated using SEM and Energy Dispersive Spectroscopy (EDS). Grafted polyamines on polydopamine surface modifications result in a large increase of the initial deposited copper.

The fast growing market of organic electronics, including organic photovoltaics (OPV), stimulates the development of versatile technologies for structuring thin-film materials. Ultraviolet lasers have proven their full potential for patterning single organic layers, but in a multilayer organic device the obtained layer selectivity is limited as all organic layers show high UV absorption. In this paper, we introduce mid-infrared (IR) resonant ablation as an alternative approach, in which a short pulse mid-infrared laser can be wavelength tuned to one of the molecular vibrational transitions of the organic material to be ablated. As a result, the technique is selective in respect of processing a diversity of organics, which usually have different infrared absorption bands. Mid-IR resonant ablation is demonstrated for a variety of organic thin films, employing both nanosecond (15 ns) and picosecond (250 ps) laser pulses tunable between 3 and 4 microns. The nanosecond experimental set-up is based on a commercial laser at 1064 nm pumping a singly resonant Optical Parametric Oscillator (OPO) built around a Periodically-Poled Lithium Niobate (PPLN) crystal with several Quasi-Phase Matching (QPM) periods, delivering more than 0.3 W of mid-IR power, corresponding to 15 μJ pulses. The picosecond laser set-up is based on Optical Parametric Amplification (OPA) in a similar crystal, allowing for a comparison between both pulse length regimes. The wavelength of the mid-infrared laser can be tuned to one of the molecular vibrational transitions of the organic material to be ablated. For that reason, the IR absorption spectra of the organic materials used in a typical OPV device were characterized in the wavelength region that can be reached by the laser setups. Focus was on OPV substrate materials, transparent conductive materials, hole transport materials, and absorber materials. The process has been successfully demonstrated for selective thin film patterning, and the influence of the various laser parameters is discussed.

Superabsorbent polymers (SAPs) are particles which can take up a significant amount of fluid. In this paper workability, microstructure and strength properties were compared for mixtures with(out) SAPs and with(out) additional water. SAP particles reduce the flow, cause a densification of the matrix due to internal curing and also reduce the strength due to macro-pore formation. These characteristics need to be taken into account when using high amounts of SAPs in a mixture. The microstructure of mixtures with SAPs and additional water tends towards the one of the reference mixture without SAPs. The strength upon water addition, however, decreases slightly.

Injectable composites for tissue regeneration can be developed by dispersion of inorganic microparticles and cells in a hydrogel phase. In this study, multifunctional carbonate microparticles containing different amounts of calcium, magnesium and zinc were mixed with solutions of gellan gum (GG), an anionic polysaccharide, to form injectable hydrogel-microparticle composites, containing Zn, Ca and Mg. Zn and Ca were incorporated into microparticle preparations to a greater extent than Mg. Microparticle groups were heterogeneous and contained microparticles of differing shape and elemental composition. Zn-rich microparticles were 'star shaped' and appeared to consist of small crystallites, while Zn-poor, Ca- and Mg-rich microparticles were irregular in shape and appeared to contain lager crystallites. Zn-free microparticle groups exhibited the best cytocompatibility and, unexpectedly, Zn-free composites showed the highest antibacterial activity towards methicilin-resistant Staphylococcus aureus. Composites containing Zn-free microparticles were cytocompatible and therefore appear most suitable for applications as an injectable biomaterial. This study proves the principle of creating bi- and tri-elemental microparticles to induce the gelation of GG to create injectable hydrogel-microparticle composites.

Laser ablation proved to be a reliable micro-fabrication technique for patterning and structuring of both thin film and bulk polymer materials. In most of the industrial applications ultra-violet (UV) laser sources are employed, however they have limitations such as maintenance costs and practical issues. As an alternative and promising approach, mid-infrared resonant laser ablation (RIA) has been introduced, in which the laser wavelength is tuned to one of the molecular vibrational transi-tions of the polymer to be ablated. Consequently, the technique is selective in respect of processing a diversity of polymers which usually have different infrared absorption bands. In this paper, we present mid-infrared resonant ablation of PolyMethyl MethAcrylate (PMMA), employing nanosec-ond laser pulses tunable between 3 and 4 microns. This RIA nanosecond laser set-up is based on a commercial laser at 1064 nm pumping a singly resonant Optical Parametric Oscillator (OPO) built around a Periodically-Poled Lithium Niobate (PPLN) crystal with several Quasi-Phase Matching (QPM) periods. RIA has been successfully demonstrated for structuring bulk PMMA, and selective patterning of PMMA thin films on a glass substrate has been implemented.

Item does not contain fulltext Thermosensitive chitosan hydrogels containing sodium beta-glycerophosphate (beta-GP), whose gelation is induced by increasing temperature to body temperature, were functionalized by incorporation of alkaline phosphatase (ALP), an enzyme involved in mineralization of bone. ALP incorporation led to acceleration of gelation upon increase of temperature for four different chitosan preparations of differing molecular weight, as demonstrated by rheometric time sweeps at 37 degrees C. Hydrogels containing ALP were subsequently incubated in calcium glycerophosphate (Ca-GP) solution to induce their mineralization with calcium phosphate (CaP) in order to improve their suitability as materials for bone replacement. Incorporated ALP retained its bioactivity and induced formation of CaP mineral, as confirmed by SEM, FTIR, Raman spectroscopy, XRD, ICP-OES, and increases in dry mass percentage, which rose with increasing ALP concentration and incubation time in Ca-GP solution. The results demonstrate that ALP accelerates formation of thermosensitive chitosan/beta-GP hydrogels and induces their mineralization with CaP, which paves the way for applications as injectable bone replacement materials.

The fast-growing market of organic electronics stimulates the development of versatile technologies for structuring thin-film materials. Ultraviolet lasers have proven their full potential for patterning organic thin films, but only a few studies report on interaction with thin-film barrier layers. In this paper, we present an approach in which the laser patterning process is optimized together with the barrier film, leading to a highly selective patterning technology without introducing barrier damage. This optimization is crucial, as the barrier damage would lead to moisture and oxygen ingress, with accelerated device degradation as a result. Following process optimization, a laser processed flexible organic LED has been fabricated and thin-film encapsulated and its operation is shown for the first time in atmospheric conditions.

Acceleration protocol plays an important role on barriers reliability evaluation for encapsulation of long-term implantable medical devices. Typically, acceleration is realized by performing tests at elevated temperature: the higher the selected temperature, the higher the acceleration factor. Nevertheless, at high temperatures, reaction mechanisms might be different, resulting in false acceleration test results. Our standard barrier performance test is based on the evaluation of corrosion of copper patterns (resistivity check, Electroscopic Impedance Spectroscopy (EIS), microscopic inspection). The temperature window for accelerated testing has been investigated for our standard barrier tests. The copper patterns, protected by a barrier layer under test, are immersed in PBS (Phosphate Buffered Saline) at temperatures up to 95°C. As barriers the following material/multilayers are selected: (1) Al2O3 ALD, (2) stacked HfO2/Al2O3/HfO2 ALD (further called ALD-3), (3) polyimide, and (4) polyimide/ALD-3/polyimide. In this presentation, the results of the test protocol evaluation will be presented. As expected, the maximum applicable test temperature is dependent on the barrier under test. Furthermore, during the fine-tuning of the accelerated test protocol, we observed for some barriers a clear influence of the shape of the Cu test patterns on the barrier performance. This can be related with processing effects when fabricating the barrier on the copper patterns. This finding stresses the determination of relevant copper patterns -or test structures in general- in order to predict the barrier performance correct for each individual application.

Hydrogel mineralization with calcium phosphate (CaP) and antibacterial activity are desirable for applications in bone regeneration. Mineralization with CaP can be induced using the enzyme alkaline phosphatase (ALP), responsible for CaP formation in bone tissue. Incorporation of polyphenols, plant-derived bactericidal molecules, was hypothesized to provide antibacterial activity and enhance ALP-induced mineralization. Three phenolic rich plant extracts from: (i) green tea, rich in epigallocatechin gallate (EGCG) (herafter referred to as EGCG-rich extract); (ii) pine bark and (iii) rosemary were added to gellan gum (GG) hydrogels and subsequently mineralized using ALP. The phenolic composition of the three extracts used were analyzed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MSn). EGCG-rich extract showed the highest content of phenolic compounds and promoted the highest CaP formation as corroborated by dry mass percentage meassurements and ICP-OES de-termination of mass of elemental Ca and P. All three extracts alone exhibited antibacterial activity in the following order EGCG-rich > PI > RO, respectively. However, extract-loaded and mineralized GG hydro-gels did not exhibit appreciable antibacterial activity by diffusion test. In conclusion, only the EGCG-rich extract promotes ALP-mediated mineralization.

The fast growing market of organic electronics, including organic light emitting diodes (OLEDs), stimulates the development of versatile technologies for structuring thin-film materials. Ultrafast diode-pumped solid-state (DPSS) lasers have proven their full potential for patterning transparent conductors, but only few studies report on interaction with thin-film barrier layers. Indeed, in the case of flexible organic applications, thin-film barrier layers consisting of inorganic and sometimes inorganic/organic multi-layers are usually used for protection. This severely restricts the selection of suitable laser patterning conditions, as damaging the barrier stack will result in moisture and oxygen ingress, leading to accelerated device degradation. In this paper we present picosecond laser processes for selective patterning conductive polymers like poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), without damaging the barrier, as well as for selective patterning the top encapsulation, without damaging the anode or cathode contacts. Careful examination using optical profilometry, SEM and chemical surface analysis reveals the importance of the laser wavelength (1064nm, 532nm, 355nm), pulse duration, pulse frequency, pulse energy, spot size, laser fluence, and pulse overlap. The fundamental laser material interaction is discussed for thin-film material stacks, and the material removal is believed to be driven by photomechanical and photochemical processes. After optimisation of the individual processes, the development of generic subtractive laser processes for industrial OLED manufacturing is discussed, with focus on process quality and speed.

The use of electronic microsystems as medical implants gains interests due to the combination of superior device functionality with extreme miniaturization. Electronic devices are not biocompatible and will suffer from corrosion, hence a very good hermetic device encapsulation is of utmost importance. The hermetic sealing of implantable electronics requires extremely good bi-directional barrier properties against diffusion of water, ions and gases. Moreover, extremely long biostability against body fluids and biomolecules is an important requirement for the barrier materials. In this work, an ALD multilayer of AlOx and HfOx in combination with flexible polyimide is used as a flexible hermetic encapsulation of an electronic CMOS chip which serves as an implantable probe (so called hd TIME (active high-density transverse intrafascicular microelectrode) probe) for neural recording and stimulation [1]. The main part consists of a 35μm thin CMOS chips with electrodes on top encapsulated with alternating layers of spin coated polyimide (PI2611) and biocompatible ALD layers. The total encapsulation is developed to provide excellent barrier properties. Each ALD stack (ALD-3) consists of AlOx (20 nm) capped on both sides with HfOx (8 nm) to avoid hydrolysis of AlOx. The ALD deposition temperature is 250°C. Special attention is payed to the adhesion of the ALD layers toward polyimide and vice versa. 3 to 4 PI/ALD-3 dyads are used for the total encapsulation, since long term implantation of the medical device is envisaged. Testing however is done using only a part of the total encapsulation, in order to enable to learn about the barrier properties in a reasonnable timeframe. The WVTR of a PI/ALD-3/PI film reached a value of 2.1 10-5 g/m2day (38°C and 100% RH), the total encapsulation with 3 to 4 dyads will lead to WVTR’s in the order of 10-6g/m2day. The same PI/ALD-3/PI film has been deposited on structured copper meanders and is exposed to PBS at 60°C for 3.5 years (equivalent to 17.5 years at 37°C) [2]. Up till now, no change in Cu resistivity has been observed proving the excellent barrier properties of the PI/ALD-3/PI film. [1] Rik Verplancke et al., 2020 J. Micromech. Microeng., 30, 015010 [2] Changzheng Li et al. 2019 Coatings, 9, 579

The deposition of gold nanoparticles (AuNPs) on the surface of gold electrode is believed to enhance the electrochemical characteristics of the surface. According to the existing literature, this could be performed in various ways. The purpose of the current study was to compare these results and report the most effective technique. In this regard, the layer-by-layer deposition, self-assembled monolayer technique and electro deposition method were investigated. Our results showed that cyclic voltammetry electrodeposition of AuNPs causes an observable increase in the peak current, causing improved electrode kinetics and a reduction in the oxidation potential (thermodynamically feasible reaction). These modified electrodes also showed several advantages with respect to stability and reproducibility.