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Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, expressed in a variety of cell types and in all tissues, control excitation and rhythm. Since their discovery in neurons and cardiac pacemaker cells, they attracted the attention of medicinal chemistry and pharmacology as novel targets to shape (patho)physiological mechanisms. To date, ivabradine represents the first-in-class drug as specific bradycardic agent in cardiac diseases; however, new applications are emerging in parallel with the demonstration of the involvement of different HCN isoforms in central and peripheral nervous system. Hence, the possibility to target specific isoforms represents an attractive development in this field; indeed, HCN1, HCN2 or HCN4 specific blockers have shown promising features in vitro and in vivo, with remarkable pharmacological differences likely depending on the diverse functional role and tissue distribution. Here, we show a recently developed compound with high potency as HCN2–HCN4 blocker; because of its unique profile, this compound may deserve further investigation.

Effective targeting of α

Nowadays, polymer based additive manufacturing (AM) is widely recognized as a powerful technology for the fabrication of complex three-dimensional objects of virtually any shape in a time, material, and cost effective way. Thanks to their characteristic advantages over conventional manufacturing strategies, AM technologies are the subject of relevant research efforts. In particular, great attention is placed on developing novel 3D printable materials characterized by improved properties and, among all, by novel functionalities, such as magnetic [1] and conductive properties [2]. In order to do this, the most common strategy relies on doping polymeric matrices with nanoparticles, obtaining thus functional 3D printable polymeric composites. Metal containing composites, in particular, can be exploited for their magnetic properties or for their mechanical behavior but also for their potential capability to trigger electroless deposition. It is well-known that electroless plating requires the presence of a catalytic surface, which can be constituted by the metallic particles embedded in the 3D printed composite. In this way, the need to activate the surface of non-conductive polymeric 3D printed parts can be avoided [3]. In addition, metallization can be carried out selectively by fabricating parts in a multi-material printing process [4] with both metal loaded and non-loaded materials. Since only the layers that contain the particles can metallize, conductive regions can be alternated with insulating zones to create metallic functional patterns on the surface of printed parts. This approach can enable the 3D printing of selectively self-metallizing parts, with possible applicability in the production of flexible and highly tridimensional electronic circuits, radiofrequency devices, microelectromechanical systems or microfluidic setups. The present work focuses on the development of a stereolithography (SLA) printable composite based on an acrylate resin loaded with nickel microparticles and its application as self-catalytic material for electroless metallization. This approach, unprecedented for SLA resins, eliminates the need of noble metal activation of the surface. Moreover, the usage of Ni is of great interest also due to the other properties that it can potentially impart to the printed parts: improved mechanical properties, high thermal conductivity, magnetizability. The SLA printability of the metal-loaded resin is assessed and the morphological properties of the 3D printed composites are investigated. Subsequently, the functional properties of the composites are determined, placing a particular emphasis on their capability to trigger NiP and Cu electroless deposition. Finally, the possibility to selectively metallize only specific areas is successfully demonstrated by metallizing a Ni-loaded pattern printed on a Ni-free base. [1] Huber et al.; Appl. Phys. Lett. 109, 162401 (2016) [2] Postiglione et al.; Compos. Part A Appl. Sci. Manuf. 76, 110-114 (2015) [3] Bernasconi et al.; J. Electrochem. Soc. 164, B3059–B3066 (2017) [4] Choi et al.; J. Mater. Process. Technol. 211, 318–328 (2011)

Gold nanoparticles (AuNPs) show physicochemical and optical functionalities that are of great interest for spectroscopy-based detection techniques, and especially for surface enhanced Raman spectroscopy (SERS), which is capable of providing detailed information on the molecular content of analysed samples. Moreover, the introduction of different moieties combines the interesting plasmonic properties of the AuNPs with the specific and selective recognition capabilities of the antibodies (Ab) towards antigens. The conjugation of biomolecules to gold nanoparticles (AuNPs) has received considerable attention for analysis of liquid samples and in particular biological fluids (biofluids) in clinical diagnostic and therapeutic field. To date, gold nanostars (AuNSts) are gaining more and more attention as optimal enhancers for SERS signals due to the presence of sharp branches protruding from the core, providing a huge number of “hot spots”. To this end, we focused our attention on the design, optimization, and deep characterization of a bottom up-process for (i) AuNPs increasing stabilization in high ionic strength buffer, (ii) covalent conjugation with antibodies, while (iii) retaining the biofunctionality to specific tag analyte within the biofluids. In this work, a SERS-based substrate was developed for the recognition of a short fragment (HA) of the hemagglutinin protein, which is the major viral antigen inducing a neutralizing antibody response. The activity and specific targeting with high selectivity of the Ab-AuNPs was successfully tested in transfected neuroblastoma cells cultures. Then, SERS capabilities were assessed measuring Raman spectra of HA solution, thus opening interesting perspective for the development of novel versatile highly sensitive biofluids sensors.

Liquid biopsies represent a minimally invasive tool for the precocious diagnosis of widespread diseases as well as for routinely patients monitoring by tracking selective biomarkers. Optical detection techniques based on surface enhanced Raman spectroscopy (SERS) are capable of providing information on the molecular content of analyzed samples thus representing one of the most promising analytical method in clinical research, as alternative to traditional bioassays. With the attempt to realize point-of-impact diagnostic devices, in the present study 3D printing and soft-lithography processes were combined with plasmonic nanoparticles (NPs) synthesis for the development of multifunctional lab-onchips (LOCs) integrating SERS sensors for liquid probing. As a matter of fact, LOCs enable to easily handle small volumes of samples as well as to perform multifunctional analyses. This is crucial for pathologies whose diagnosis relies on the ratio of more than one biomarker. To this end, being based on a 3D printing process, the overall design of the devices was rapidly prototyped to integrate channels and detection chambers aligned with optical fibers and portable Raman probes for signal delivering and collection. SERS functionality was achieved by immobilization of gold NPs whose chemistry was modified to enhance NPs deposition and stability. Finally, we are exploring direct laser writing for the integration of mechanical and optical microcomponents needed for liquids control and signal delivering and collection, respectively. The final devices collecting multiple functions and detection configurations will provide high sensitivity, speed of analysis, low sample and reagent consumption, measurement automation and standardization on a highly integrated dynamic platform that will revolutionize liquid biopsy making it costless, on-chip, handy and easy to use.

Surface-enhanced Raman spectroscopy (SERS) exploiting Raman reporter-labeled nanoparticles (RR@NPs) represents a powerful tool for the improvement of optical bio-assays due to RRs’ narrow peaks, SERS high sensitivity, and potential for multiplexing. In the present work, starting from low-cost and highly available raw materials such as cysteamine and substituted benzoic acids, novel bioorthogonal RRs, characterized by strong signal (103 counts with FWHM < 15 cm−1) in the biological Raman-silent region (>2000 cm−1), RRs are synthesized by implementing a versatile, modular, and straightforward method with high yields and requiring three steps lasting 18 h, thus overcoming the limitations of current reported procedures. The resulting RRs’ chemical structure has SH-pendant groups exploited for covalent conjugation to high anisotropic gold-NPs. RR@NPs constructs work as SERS nanoprobes demonstrating high colloidal stability while retaining NPs’ physical and vibrational properties, with a limit of detection down to 60 pM. RR@NPs constructs expose carboxylic moieties for further self-assembling of biomolecules (such as antibodies), conferring tagging capabilities to the SERS nanoprobes even in heterogeneous samples, as demonstrated with in vitro experiments by transmembrane proteins tagging in cell cultures. Finally, thanks to their non-overlapping spectra, we envision and preliminary prove the possibility of exploiting RR@NPs constructs simultaneously, aiming at improving current SERS-based multiplexing bioassays.

In this paper, additive manufacturing and wet metallization process are combined to fabricate three prototypes of differential electro-mechanical ${z}$ -axis accelerometers. The smart combination of existing fabrication processes makes the proposed fabrication flow unique in the sensors field. The mechanical design of the three proposed devices exploits the three-dimensionality of the 3-D-printing technique and the electrostatic differential readout is allowed thanks to the wet-metallization process of the printed structure. Experimental measurements show a very good agreement with theoretical predictions thus proving a good reliability of the proposed design flow and fabrication process. With their relative small footprints (minimum dimension in the order of hundreds of ${\mu }\text{m}$ ), good performances (sensitivity >12 fF/g, sub % linearity error up to 11 g of full scale and theoretical noise estimation of few tens of ng/ $\surd $ Hz) and high customizability, they represent an important step toward novel application fields of inertial sensors.

Optical detection techniques based on surface enhanced Raman spectroscopy (SERS) are a powerful tool for biosensing applications. Meanwhile, due to technological advances, different approaches have been investigated to integrate SERS substrates on the tip of optical fibres for molecular probing in liquids. To further demonstrate the perspectives offered by SERS-on-fiber technology for diagnostic purposes, in this study, novel cap-shaped SERS sensors for reversible coupling with customized multimodal probes were prototyped via low-cost polymer casting of polydimethylsiloxane (PDMS) and further assembly of gold nanoparticles (Au NPs) of varied sizes and shapes. To demonstrate the feasibility of liquid sensing with cap sensors using backside illumination and detection, the spectra of rhodamine were acquired by coupling the caps with the fiber. As expected by UV-vis, the highest SERS efficiency was observed for NP-decorated substrates with plasmonic properties in resonance with the irradiation wavelength. Then, SERS biosensors for the specific detection of amyloid-β (Aβ) neurotoxic biomarkers were realized by covalent grafting of Aβ antibodies. As attested by fluorescence images and SERS measurements, the biosensors successfully exhibited enhanced Aβ affinity compared to the bare sensors without ligands. Finally, these versatile (bio)sensors are a powerful tool to transform any milli-sized fibers into functional (bio)sensing platforms with plasmonic and biochemical properties tailored for specific applications.

In the present paper the electroless metallization of 3D printed devices using stereolithography is investigated. Two different photocurable resins from a commercial supplier and a self-formulated one are used as starting materials for printing. A first metal layer of NiP or Cu, obtained by an optimized pretreatment and plating process, is subsequently applied on the parts. The possibility of obtaining multilayers through the successive electrodeposition of different metals on the electroless treated parts is demonstrated as well. From the applicative point of view, the use of 3D printing, coupled with electroless deposition of mono or multilayers, can be employed to manufacture functional microstructures for use in the fields of microrobotics, MEMS, metamaterials and others. For this reason, the realization of a prototypical magnetic actuator is presented as an example of possible application.

Optical detection techniques based on surface enhanced Raman spectroscopy (SERS) and capable of providing relevant information on molecular and protein composition of biological samples, are gaining rising attention in clinical research as alternatives to traditional detection assays. Meanwhile, due to the technological advances in compact instrumentation as well as in nanofabrication processes, SERS probes based on portable guided-wave systems, have been implemented thus providing for easier accessibility into complex environments and enabling for real-time in situ detection of low concentrated target analytes. In the present study, low-cost fabrication processes were successfully combined with surface functionalization strategies for the fabrication of disposable SERS-active substrates, engineered to tightly fit the distal end of portable Raman instruments. Being based on a polymer casting fabrication process, the overall design of the substrates can be easily adapted to the varied geometry of the probes to be fit, thus guaranteeing high design versatility. SERS-functionality was achieved by immobilization of gold nanoparticles whose size and shape directly affect the plasmonic properties of the substrates. Moreover, SERS substrates can be further modified by covalently binding molecules acting as baits to selectively fish target biomarkers within heterogeneous samples thereby increasing the specificity of SERS signals. Finally, these sensors represent a powerful tool potentially implementable for the early diagnosis of widespread pathologies by real-time SERS analysis of liquid biopsy.

Microrobotic prototypes for water cleaning are produced combining stereolithography 3D printing and wet metallization. Different metallic layers are deposited on 3D printed parts using both electroless and electrolytic deposition to impart required functionalities. In particular, by exploiting the flexibility and versatility of electrolytic codeposition, pollutants photodegradation and bacteria killing are for the first time combined on the same device by coating it with a composite nanocoating containing titania nanoparticles in a silver matrix. The microstructure of the microrobots thus obtained is fully characterized and they are successfully actuated by applying rotating magnetic fields. From the water cleaning point of view, devices show evident photocatalytic activity towards water pollutants and antimicrobial activity for gram negative bacteria., Additive Manufacturing, 28, ISSN:2214-8604

The combination of biological tissue clearing methods with light-sheet fluorescence microscopy (LSFM) allows acquiring images of specific biological structures of interest at whole organ scale and microscopic resolution. Differently to classical epifluorescence techniques, where the sample is cut into slices, LSFM preserves the whole organ architecture, which is of particular relevance for investigations of long-range neuronal circuits. This imaging modality comes with the need of new protocols for sample mounting. Gel matrix, hooks, tips, glues, and quartz cuvettes have been used to keep whole rodent organs in place during image acquisitions. The last one has the advantage of avoiding sample damage and optical aberrations when using a quartz refractive index (RI) matching solution. However, commercially available quartz cuvettes for such large samples are expensive. We propose the use of polydimethylsiloxane (PDMS) for creating tailor-made cuvettes for sample holding. For validation, we compared PDMS and quartz cuvettes by measuring light transmittance and performing whole mouse-brain imaging with LSFM. Moreover, imaging can be performed using an inexpensive RI matching solution, which further reduces the cost of the imaging process. Worth of note, the RI matching solution used in combination with PDMS leads to a moderate expansion of the sample with respect to its original size, which may represent an advantage when investigating small components, such as neuronal processes. Overall, we found the use of custom-made PDMS cuvettes advantageous in term of cost, image quality, or preservation of sample integrity with respect to other whole-mouse brain mounting strategies adopted for LSFM.

Novel localised surface plasmon resonance-based sensors exploitable as diagnostic devices through surface enhanced Raman scattering (SERS) represent a powerful solution for the analysis of liquid samples. In this work, we developed a rapid, versatile, low-cost and time-saving strategy combining advanced (3D-printing) and traditional manufacturing (replica molding) processes to prototype polymeric microfluidic devices, integrating all the components into a single portable platform. Microfluidics provide multiplexed capability, adequate miniaturization and robustness, handling simplicity, reliability, as well as low sample and reagents consumption, while the use of polydimethylsiloxane as supporting substrate drastically reduces the final cost. To introduce SERS capability, plasmonic features were incorporated functionalizing substrates with gold nanoparticles (NPs), engineered in terms of shape, size and surface chemistry to play with plasmonic properties as well as to guarantee reproducibility to the NPs immobilization step and consequently to the SERS effect for signal enhancing. To assess the feasibility of the measurements for molecules optical targeting, SERS-microfluidic systems were synergically coupled with a portable fiber-based set-up and Raman spectra of rhodamine 6 G at different concentrations were acquired. To further demonstrate the potentiality of developed SERS-based substrates as point-of-care devices, Raman analysis were successfully implemented on aqueous solutions of amyloid-β 1–42 (Aβ), considered the main biomarkers for Alzheimer’s disease.

In recent years, 3D-printing techniques are attracting increasing interest because of the variety of possible applications (i.e. biomedical applications, design), the large versatility and relative low-costs. Moreover, by combining the 3D-printing technology with other processes (i.e. wet metallization), it is possible to provide an innovative, high-customizable and cheap fabrication procedure for sensors, such as accelerometers. In this work, the design and the fabrication of a uniaxial and a multi-axial accelerometers are proposed from the simulation to the final prototyping.

The combination of 3D printing and wet metallization is a promising methodology for the manufacturing of functional microdevices able to carry out biomedical tasks in vivo. Following this approach, prototypical cell scaffolds are successfully manufactured in the present work. Functional layers are sequentially deposited employing electroless metallization on stereolitography 3D printed moveable structures. Final devices are characterized and magnetically actuated in a precise way using a novel rolling motion approach, which allows for a superior control over speed and position. From the living cells compatibility point of view, the scaffolds show good biocompatibility with fibroblasts after the application of a gold layer., Materials Horizons, 5 (4), ISSN:2051-6347, ISSN:2051-6355

Chemically crosslinked hyaluronic acid hydrogels are synthesized with a homogeneous crosslinking process using divinyl sulfone (DVS) as crosslinking agent. Testing different conditions, in terms of both DVS content and curing time, we aim to keep control over the crosslinking process in order to prepare biocompatible hydrogels with mechanical properties closely approximating those of extracellular matrix (ECM) of natural stem cells niches (0.1÷50kPa). The hydrogels properties are evaluated through a reliable methodology based on three independent techniques: dynamic rheological analysis, used as benchmark method; swelling experiments following the Flory-Rehner theory and atomic force microscope (AFM) nanoindentation experiments. Our results demonstrate that controlling crosslinking parameters it is possible to design hydrogels with desired elastic moduli values. HA hydrogels can be ideal coating materials to be implemented in regenerative medicine and particularly in the engineering of ECM niches in vitro.

In this work, we provide a simple and straightforward method for the fabrication of stable highly hydrophobic and oleophobic surfaces by applying stereolithography (SL) to perfluoropolyethers (PFPEs). Inspired by the liquid repellency widely shown in nature, our approach enables to easily mimic the interplay between the chemistry and physics by microtexturing low surface tension PFPEs. To this end, UV-curable resins suitable for SL-processing were formulated by blending multifunctional (meth-)acrylates PFPEs oligomers with photoinitiator and visible dyes whose content was tuned to tailor resin SL sensitivities. Photocalorimetric studies were also performed to investigate the curing behavior of the different formulations upon SL light exposure. Being the first example of stereolithography applied to PFPEs, stereolithographic processability of new developed PFPEs photopolymer was compared with a standard photoresist taken as benchmark (DL260®). Optimized formulations were characterized by reduced laser penetration depth (

A strategy combining stereolithography (SL) and soft-lithography for the straightforward fabrication of superhydrophobic bulk devices is reported. Microtextured masters are rapidly prototyped by SL and passivated with a perfluorosilane. Such surface treatment enables the faultless fabrication of negative microstructured polydimethylsiloxane molds ultimately utilized to obtain bulk polymeric micropatterned structures by replica molding. As illustrative proof of concept, this approach is employed in the field of photovoltaics to realize the first example of superhydrophobic luminescent solar concentrators (LSCs) showing superior self-cleaning properties. Following our strategy, a new dye-doped acrylate mixture is developed and optimized to ensure complete wetting of the hollow microstructures present on the mold. By judiciously tailoring the photoinitiator concentration and by implementing a tailored double-step UV-irradiation process, complete UV-photopolymerization is achieved despite the significant thickness of the target samples. The high fidelity replication of the original SL-printed features on the daughter replicas as well as their super water-repellency are successfully demonstrated. The performance of the resulting superhydrophobic LSCs is investigated at varying device dimensions and found to be comparable with state-of-the-art systems. This study demonstrates the potential of high-resolution SL-printing in combination with replication techniques as a versatile tool to reproducibly fabricate microstructured superhydrophobic polymeric bulk devices in a straightforward fashion. Keywords: 3D printing, Stereolithography, Replica molding, Fluoropolymers, Luminescent solar concentrators, Superhydrophobic surfaces

In the present paper the electroless metallization of 3D printed parts using stereolithography is investigated. Two different photocurable resins of large commercial diffusion and a self-formulated one are used as starting materials for printing. A first metal layer of NiP or Cu, obtained by an optimized pretreatment and plating process, is subsequently applied on the parts. It is also demonstrated the possibility of obtaining multilayers through the successive electrodeposition of different metals on the electroless treated parts. The resulting layers are characterized by SEM and profilometry.

A method for the reconstruction of a vessel centerline from angiographic images is outlined in this work. A typical coronary artery segment with bifurcations was emulated with a 3D printed static phantom and several angiograms were acquired at various angular positions on the C-Arm. The effectiveness of the reconstruction turned out to be largely influenced by the intrinsic parameters of the angiographic system, particularly the homogeneous coordinates system scaling factor λ. Therefore, recourse was made to a heuristic optimization method to estimate the optimal value of λ for each view. We measured the reliability of the reconstruction method by varying the fitness function of the optimization step and measuring the distances of 8 test points in comparison to the corresponding points identified in the μCT centerline. Preliminary results showed that, with an adequate number of views, the adoption of the optimal fitness function allowed the median distance error to be decreased below the acceptance threshold of 10%. As expected, the reliability of the method is improved by increasing the number of processed views.

A simple photolithographic process for directly patterning glycidyl methacrylate modified hyaluronic acid features onto UV curable perfluoropolyether-based surfaces is presented. Due to the versatility of the developed method, HA spotted areas with different geometrical features could be rapidly and inexpensively designed. In addition, the excellent antifouling and fouling-release properties of the substrates enabled direct HA baits photo-grafting onto PFPEs without further surface passivation or chemical modification to avoid not specific adsorption. The aim of the study was to locally switch the surface properties of the PFPEs from cells and protein repulsive to adherent. Particularly, we exploited HA well-known preferential interactions with CD44 transmembrane receptors to selectively immobilize cancer cells. Living cell arrays offer a higher-resolution visualization of HA-CD44 interactions and may provide a deep insight into understanding molecular mechanisms needed to develop selective therapies and diagnosis against tumor growth.

Advancements in understanding stem cell functions and differentiation are of key importance for the clinical success of stem-cell-based therapies. 3D structural niches fabricated by two-photon polymerization are a powerful platform for controlling stem cell growth and differentiation. In this paper, we investigate the possibility of further controlling stem cell fate by tuning the mechanical properties of such niches through coating with thin layers of biomimetic hyaluronan-based and gelatin-based hydrogels. We first assess the biocompatibility of chemical coatings and then study the interactions between structural and chemical biomimetism on the response of MSCs in terms of proliferation and differentiation. We observed a clear effect of the hydrogel coating on otherwise identical 3D scaffolds. In particular, in gelatin-coated niches we observed a stronger metabolic activity and commitment toward the osteo-chondral lineage with respect to hyaluronan-coated niches. Conversely, a reduction in the homing effect was observed in all the coated niches, especially in gelatin-coated niches. This study demonstrates the feasibility of controlling independently different mechanical cues, in bioengineered stem cell niches, i.e. the 3D scaffold geometry and the surface stiffness. This will allow, on the one hand, understanding their specific role in stem cell proliferation and differentiation and, on the other hand, finely tuning their synergistic effect.

The present work reports the first demonstration of straightforward fabrication of monolithic unibody lab-on-a-chip (ULOCs) integrating bioactive micrometric 3D scaffolds by means of multimaterial stereolithography (SL). To this end, a novel biotin-conjugated photopolymer is successfully synthesized and optimally formulated to achieve high-performance SL-printing resolution, as demonstrated by the SL-fabrication of biotinylated structures smaller than 100 µm. By optimizing a multimaterial single-run SL-based 3D-printing process, such biotinylated microstructures are incorporated within perfusion microchambers whose excellent optical transparency enables real-time optical microscopy analyses. Standard biotin-binding assays confirm the existence of biotin-heads on the surfaces of the embedded 3D microstructures and allow to demonstrate that the biofunctionality of biotin is not altered during the SL-printing, thus making it exploitable for further conjugation with other biomolecules. As a step forward, an in-line optical detection system is designed, prototyped via SL-printing and serially connected to the perfusion microchambers through customized world-to-chip connectors. Such detection system is successfully employed to optically analyze the solution flowing out of the microchambers, thus enabling indirect quantification of the concentration of target interacting biomolecules. The successful application of this novel biofunctional photopolymer as SL-material enables to greatly extend the versatility of SL to directly fabricate ULOCs with intrinsic biofunctionality.

3D printing is currently finding an increasing number of applications in many different fields. This technique, relegated for years to high-end rapid prototyping due to its high costs, is now acquiring industrial relevance for the direct fabrication of objects. The well-known advantages of scalability, production rate and the possibility to produce shapes otherwise impossible to manufacture with conventional techniques are at the base of the exponential market growth of additive manufacturing technologies. Such advantages apply not only to the production of macroscopic structures, a practice already well implemented in the current practice, but also to the manufacturing of microscopic objects. 3D printing of functional devices in the millimetric and sub-millimetric dimensional range can be challenging due to the high resolution needed, in the order of tens of micrometers. This result is possible using only some of the technologies available: stereolithography (SLA), two photons lithography (2PL) or selective laser sintering (SLS). However, all these techniques are characterized by the same drawback: the difficulty to work with metals. Metallic parts are used when the functional structures produced must interact with magnetic fields or must be electrically/thermally conductive. Only selective laser sintering (SLS) is able to work on metallic parts with sufficient precision, but typically the objects does not have the same properties of a bulk counterpart, either forged or machined. A possible solution to get metallic properties on 3d printed objects is to impart them only to the surface via external metallization. Particularly advantageous from this point of view are the wet metallization techniques, thanks to their low cost and high productivity rates. The handling of very small parts is however difficult and, for this reason, suitable approaches must be developed. An approach to the plating of millimetric objects have already been investigated [1]. In that case, Cu and a CoNiP alloy were applied to freestanding 3D printed microdevices using a fully electroless process. The approach presented is characterized however by significant drawbacks, the first one being that only electroless alloys can be deposited. As an example, high performances hard magnetic alloys like CoPt are impossible to deposit. A second disadvantage is connected to the plating rate: electroless deposition must be carried out at low temperatures due to the physical characteristics of the 3D printing resins, and this strongly limits plating rate. Another possible approach to apply a metallic layer on a 3D printed microstructure is the application of an hybrid electroless/electrolytic metallization route. A first layer of a metal is electroless applied, according to previous literature [2], to make the surface of the resin conductive. Once a first layer of metal covers the surface, electrolytic deposition can be used to deposit the functional coating. This technique is described in the present work, where two methods are used to contact the object with the current generator. The first one is the exploitation of the 3D printing supports, generally used during the 3D printing steps, as electrical contacts. The second one is the use of a modified version of barrel plating. Functionality and performances of the two approaches are studied on prototypical microdevices printed via SLS. Finally, an applicative example is presented. The method described can find application in many sectors, including the production of magnetically controlled micromanipulators [3] or the additive manufacturing of MEMS. [1] ECS Meeting Abstract MA2016-01 1105 [2] R. Bernasconi, C. Credi, G. Natale, M. Tironi, F. Cuneo, M. Levi and L. Magagnin; ECS Trans. 72, issue 21 (2016) 9-21 [3] S. Kim, F. Qiu, S. Kim, A. Ghanbari, C. Moon, L. Zhang, B. J. Nelson and H. Choi; Adv. Mater.25 (2013) 5863-5868

In this study, nanomechanical properties of a variety of polymeric materials was investigated by means of AFM. In particular, selecting different AFM probes, poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS) bulk samples, sol–gel hybrid thin films and hydrated hyaluronic acid hydrogels were indented in air to determine the elastic modulus. The force–distance curves and the indentation data were found to be greatly affected by the cantilever stiffness and by tip geometry. AFM indentation tests show that the choice of the cantilever spring constant and of tip shape is crucially influenced by elastic properties of samples. When adhesion-dominated interactions occur between the tip and the surface of samples, force–displacement curves reveal that a suitable functionalization of AFM probes allows the control of such interactions and the extraction of Young’ modulus from AFM curves that would be otherwise unfeasible. By applying different mathematical models depending on AFM probes and materials under investigation, the values of Young's modulus were obtained and compared to those measured by rheological and dynamic mechanical analysis or to literature data. Our results show that a wide range of elastic moduli (10 kPa–10 GPa) can be determined by AFM in good agreement with those measured by conventional macroscopic measurements.

Perfluoropolyether polymers have been described as high performance fouling-release materials for marine coatings. Moreover, they have a good potential to be exploited in the biomedical field too. In this article several perfuoropolyether photopolymers were characterized in terms of surface and mechanical properties outlining the relationship between these properties and the polymer molecular structure. In particular the anti-fouling and fouling-release performances, evaluated using Bovine Serum Albumin as testing protein, was correlated to other material properties, like a parameter considering both surface tension components γ and elastic modulus E . A good correlation between the anti-fouling/fouling-release of perfluoropolyethers and ( E * γ polar ) 1/2 can actually be established. Our results show that perfluoropolyether photopolymers are good protein anti-fouling/fouling-release materials.

Withstanding high pressures in polymeric microchannels is an important requirement for many biological applications. Here, a simple direct polymerization through a polyester photomask is applied to obtain monolithic polyethylene glycol (PEG)-modified poly(methyl methacrylate) (PMMA) (PEGMA) microchannels, showing the ability to withstand pressure up to 12 MPa in burst pressure tests. The ability of withstanding high pressures is observed to increase with increasing ratio between the thickness of the cover polymer layer forming the microchannel lid and the width of the microchannel. A simplified finite element modeling model of the burst pressure test is set up to interpret the experimental findings. The outcomes of the modeling activity, along with direct scanning electron microscopy observation of the fracture surfaces, confirm the effectiveness of the polymerization method for the production of monolithic PEGMA microchannels. (C) 2014 Wiley Periodicals, Inc.

In the last few decades additive manufacturing is finding applications in the field of microdevices production. Techniques like sterolithography (SLA), two photons lithography (TPL) and others [1] have the potential to reach the micrometric scale required for the realization of devices like polymeric based microelectromechanical systems (MEMS) or magnetically actuated microdevices. The most precise and versatile additive technologies however use polymers as materials. For this reason a fundamental step of the manufacturing process is the application of a metallic layer to provide conductivity, essential for MEMS, or to make sensitive the device to the presence of a magnetic field. Many different metallization methods can be applied, but one of the most attractive in terms of cost and flexibility is electroless deposition [2]. The use of this all-wet technique introduce however some major issues when plating on the resins usually employed in SLA or TPL. The main problem is in particular related to the temperatures typical of some electroless baths, which makes them incompatible with polymers that in some cases present reversible transition temperatures as low as 40 °C. To successfully metallize SLA and TPL resins a great attention must be devoted to the choice and optimization of compatible electroless processes. Between the possible metallic layers that can be applied in relation to the type of microstructure produced, hard magnetic alloys are of great interest. Such materials, and in particular their ability to retain magnetization, can be used to actuate or manipulate different classes of devices. Examples may include magnetically actuated microswitches, sensors or others [3]. In the present work two processes to deposit hard magnetic CoNiP, operating at two different temperatures, are presented and applied to the plating of microsized functional structures. The main advantages or disadvantages of using one temperature with respect to the other are discussed as a function of the target application. Some general problems related to the plating of stereolithography printed small structures are analyzed as well. These include difficulties coming from the chemical and physical properties of the resins, from the activation step or from the solution itself. [1] M. Vaezi, H. Seitz, S. Yang; Int. J. Adv. Manuf . Technol. (2013) 67, 1721–1754 [2] Y. Yan, A. A. Bettiol, Photonics Global Conference (PGC), 2010, pp. 1 – 4 [3] S. Kim et al.; Adv. Mater. 2013, DOI: 10.1002/adma.201301484

The manufacture of manipulators able to work wirelessly on a micrometric scale is one of the most interesting topics in microfabrication. Such devices, called microrobots, are expected to deeply change some aspects of modern surgery and to make in particular some medical treatments less invasive. Possible applications include localized drug delivery or confined modification of living tissues. Since motion in fluids at the microscale usually happens in low Reynolds number regime, the shape of microrobots is in general inspired by natural structures like bacterial flagella [1] or other propulsion apparatus of living cells well adapted to such conditions. For this reason shapes like rods, flagella [1] and helixes [2] have been tested in the existing literature. The most used method to control the motion of the devices is the application of a magnetic field [3], and due to this the microswimmers must have at least a part made of a metallic magnetic alloy. Microrobots are nowadays realized using standard lithographic techniques, with high costs and poor flexibility of the production process. From this point of view the introduction of a manufacturing route based on additive manufacturing can introduce significant advantages. In the present work the possibility to directly 3D print the microrobots employing stereolithography (SLA) as technique is investigated. Typical designs like rods and helixes are employed. Since the SLA printing of metals is problematic, photocurable resins are used to produce the devices and the obtained samples are metallized via electroless plating to obtain the magnetic coating necessary for magnetic actuation. The quality of the 3D printed microrobots is evaluated, while the electroless process is first characterized from the general point of view and subsequently applied to the metallization of the devices. A first layer of a pure metal like copper is applied as flash layer, followed by a thicker layer of a suitable magnetic alloy. Finally the microdevices thus obtained are actuated in a controlled magnetic field and the motion at low Reynold number regime is studied. [1] R. Mhanna et al.; Small 10, 1953 (2014) [2] K. E. Peyer et al.; Chem. Eur. J. 19, 28 (2013) [3] S. Kim et al.; Adv. Mater. 25, 5863 (2013)