Nano-droplets deposited in microarrays by femtosecond Ti:sapphire laser-induced forward transfer

The authors present the deposition of nanoscale droplets of Cr using femtosecond Ti:Sapphire Laser-Induced Forward Transfer. Deposits around 300 nm in diameter, significantly smaller than any previously reported, are obtained from a 30 nm thick source film. Deposit size, morphology, and adhesion to a receiver substrate as functions of applied laser fluence are investigated. We show that deposits can be obtained from previously irradiated areas of the source material film with negligible loss of deposition quality, allowing sub-spot size period microarrays to be produced without the need to move the source film

Apta- and Immuno-Sensors Performance Optimization: A Comparative Study of Surface Functionalization Techniques

Surface bio-functionalization plays a critical role in the performance of a biosensor and numerous techniques for the enhancement of a biosensor’s surface coverage with oriented capture biomolecules have been developed with the ultimate goal of optimizing a sensor’s performance in terms of its sensitivity and linear response over a wide dynamic range. Herein, highlights of a comparative assessment into the most promising approaches to achieve this goal are being presented. For aptamer-modified surfaces, polyamidoamine (PAMAM) dendrimers and polysaccharide networks were employed with the obtained results clearly indicating that a much denser surface coverage with aptamers can be achieved with the use of the latter. For the functionalization of surfaces with antibodies, the orientation and density of immobilized antibodies onto recombinant protein A/G- or boronic acid-modified substrates were compared, with the former leading not only to increased antibody loading but also with such an orientation that permits enhanced antigen binding. The conclusions reached can be used as a starting point for the customization of sensor functionalization in a plethora of clinical, environmental and even food-industry-related biosensing platforms

Comparative Assessment of Affinity-Based Techniques for Oriented Antibody Immobilization towards Immunosensor Performance Optimization

Immunosensor sensitivity and stability depend on a number of parameters such as the orientation, the surface density, and the antigen-binding efficiency of antibodies following their immobilization onto functionalized surfaces. A number of techniques have been developed to improve the performance of an immunosensor that targets one or both of the parameters mentioned above. Herein, two widely employed techniques are compared for the first time, which do not require any complex engineering of neither the antibodies nor the surfaces onto which the former get immobilized. To optimize the different surface functionalization protocols and compare their efficiency, a model antibody-antigen system was employed that resembles the complex matrices immunosensors are frequently faced with in real conditions. The obtained results reveal that protein A/G is much more efficient in increasing antibody loading onto the surfaces in comparison to boronate ester chemistry. Despite the fact, therefore, that both contribute towards the orientation-specific immobilization of antibodies and hence enhance their antigen-binding efficiency, it is the increased antibody surface density attained with the use of protein A/G that plays a critical role in achieving maximal antigen recognition

Special issue on: Laser and plasma processing for advanced applications in material science (E-MRS 2015 Spring Meeting Symposium) Preface

International audienceno abstrac

Laser Bioprinting of Cells Using UV and Visible Wavelengths: A Comparative DNA Damage Study

Laser-based techniques for printing cells onto different substrates with high precision and resolution present unique opportunities for contributing to a wide range of biomedical applications, including tissue engineering. In this study, laser-induced forward transfer (LIFT) printing was employed to rapidly and accurately deposit patterns of cancer cells in a non-contact manner, using two different wavelengths, 532 and 355 nm. To evaluate the effect of LIFT on the printed cells, their growth and DNA damage profiles were assessed and evaluated quantitatively over several days. The damaging effect of LIFT-printing was thoroughly investigated, for the first time at a single cell level, by counting individual double strand breaks (DSB). Overall, we found that LIFT was able to safely print patterns of breast cancer cells with high viability with little or no heat or shear damage to the cells, as indicated by unperturbed growth and negligible gross DNA damage

Single Step Laser Transfer and Laser Curing of Ag NanoWires: A Digital Process for the Fabrication of Flexible and Transparent Microelectrodes

Ag nanowire (NW) networks have exquisite optical and electrical properties which make them ideal candidate materials for flexible transparent conductive electrodes. Despite the compatibility of Ag NW networks with laser processing, few demonstrations of laser fabricated Ag NW based components currently exist. In this work, we report on a novel single step laser transferring and laser curing process of micrometer sized pixels of Ag NW networks on flexible substrates. This process relies on the selective laser heating of the Ag NWs induced by the laser pulse energy and the subsequent localized melting of the polymeric substrate. We demonstrate that a single laser pulse can induce both transfer and curing of the Ag NW network. The feasibility of the process is confirmed experimentally and validated by Finite Element Analysis simulations, which indicate that selective heating is carried out within a submicron-sized heat affected zone. The resulting structures can be utilized as fully functional flexible transparent electrodes with figures of merit even higher than 100. Low sheet resistance (<50 Ohm/sq) and high visible light transparency (>90%) make the reported process highly desirable for a variety of applications, including selective heating or annealing of nanocomposite materials and laser processing of nanostructured materials on a large variety of optically transparent substrates, such as Polydimethylsiloxane (PDMS)

Digital laser-induced printing of MoS2

Due to their atomic-scale thickness, handling and processing of two-dimensional (2D) materials often require multistep techniques whose complexity hampers their large-scale integration in modern device applications. Here we demonstrate that the laser-induced forward transfer (LIFT) method can achieve the one-step, nondestructive printing of the prototypical 2D material MoS2. By selecting the optimal LIFT experimental conditions, we were able to transfer arrays of MoS2 pixels from a metal donor substrate to a dielectric receiver substrate. A combination of various characterization techniques has confirmed that the transfer of intact MoS2 monolayers is not only feasible, but it can also happen without incurring significant defect damage during the process. The successful transfer of MoS2 shows the broad potential the LIFT technique has in the emerging field of printed electronics, including printed devices based on 2D materials