Life-Detection Technologies for the Next Two Decades

Since its inception six decades ago, astrobiology has diversified immensely to encompass several scientific questions including the origin and evolution of Terran life, the organic chemical composition of extraterrestrial objects, and the concept of habitability, among others. The detection of life beyond Earth forms the main goal of astrobiology, and a significant one for space exploration in general. This goal has galvanized and connected with other critical areas of investigation such as the analysis of meteorites and early Earth geological and biological systems, materials gathered by sample-return space missions, laboratory and computer simulations of extraterrestrial and early Earth environmental chemistry, astronomical remote sensing, and in-situ space exploration missions. Lately, scattered efforts are being undertaken towards the R&D of the novel and as-yet-space-unproven life-detection technologies capable of obtaining unambiguous evidence of extraterrestrial life, even if it is significantly different from Terran life. As the suite of space-proven payloads improves in breadth and sensitivity, this is an apt time to examine the progress and future of life-detection technologies.Comment: 6 pages, the white paper was submitted to and cited by the National Academy of Sciences in support of the Astrobiology Science Strategy for the Search for Life in the Univers

Formation of more stable hydrophilic surfaces of PDMS by plasma and chemical treatments

In the present work hydrophilic stability of Sylgard 184 poly(dimethyl siloxane) (PDMS) was studied with the objective to create more stable hydrophilic surfaces. The surface modification of PDMS was carried out by conventional (oxygen plasma) and unconventional plasma modification (2 step modification using oxygen and C2F6) processes and also by chemical grafting using oxygen-plasma polymerization of 2-hydroxyethyl methacrylate (HEMA). The hydrophilic stability of the modified surfaces was monitored as a function of time elapsed after treatment and quantified. The surfaces were characterized using static contact angle measurements and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR)

Hydrophilization and hydrophobic recovery ofPDMS by oxygen plasma and chemical treatment—An SEM investigation

International audienceRapid prototyping of polydimethylsiloxane (PDMS) is frequently used to build microfluidic devices. PDMS is inherently hydrophobic; however, the surface can be temporarily rendered hydrophilic by exposing the surface to oxygen plasma. Hydrophilic microchannels are sometimes advantageous over hydrophobic microchannels due to increased cell adhesion or increase in electro osmotic flow (EOF) leading to ease of liquid filling in microchannels. However, the hydrophilic surface is unstable and that low molecular weight (LMW) chains diffuse from the bulk of the PDMS and cover up the thermodynamically unstable surface. This is one reason for the hydrophilic unstability of PDMS. Present study shows that not only chemistry of the creation of silanol groups on the surface, but also morphology of the film surface nanostructuring of PDMS plays an important role in hydrophilization of PDMS. Present paper tries to understand the mechanism of hydrophobic recovery taking into consideration physical and chemical parameters using SEM characterization

Fabrication of long-term hydrophilic surfaces of poly(dimethyl siloxane) using 2-hydroxy-ethyl methacrylate

International audienceIn the present work, 2-hydroxy-ethyl-methacrylate (HEMA) was used to modify surface of poly(dimethylsiloxane)(PDMS) elastomer. Fourier transform infrared spectroscopy (FTIR) and wetting angle measurements were used for the analysis of modified surface and hydrophilic stability of PDMS. Results of the surface reconstruction reveal that long-term hydrophilic surfaces of PDMS can be achieved by use of HEMA

Direct patterning of quantum dots on structured PDMS surface

International audienceSemiconductor quantum dots are currently the most attractive research areas due to its variety of applications, especially in the field of life science. The present work deals with direct patterning of quantum dots (CdSe) using a modified hydrophobic–hydrophilic PDMS surface. The hydrophilic monomer was stamped on a hydrophobic PDMS to generate pattern of hydrophobic–hydrophilic PDMS surface. Fluorescent microscopy shows the selective deposition of quantum dots onto the hydrophobic PDMS surface

Development of nano-immunosensor with magnetic separation and electrical detection of Escherichia coli using antibody conjugated Fe3O4@Ppy

Detection of bacterial pathogens is the need of the hour due to the increase in antibiotic resistance and the infusion of multi-drug-resistant parasites. The conventional strategies such as ELISA, PCR, and MNP based tests for the detection are efficient but they are cost, time, lab, and manpower intensive. Thus, warranting a simple and effective technique for rapid detection of bacterial pathogens. Magnetic nanoparticles (NPs) have proved to be better alternatives for separation of bacterial pathogens from a variety of sample sources. However, the use of magnetic NPs has not been successful in the detection of these parasites. The current work involves the coating of magnetic NPs (Fe3O4) with a conducting polymer (polypyrrole; Ppy) to facilitate simultaneous separation and detection. Electrical (conductivity) measurement was the mode of choice due to the sensitivity, accuracy, and ease it offers. To enhance the conductivity, carboxylic groups were expressed on the Fe3O4@Ppy complex and to ensure specificity, E. coli specific antibodies were conjugated. The resulting complex at various process parameters was characterized using FTIR, VSM, and SEM. SEM images were recorded to ensure bacterial separation at optimal process parameters. The impedance analysis and conductivity measurements were carried out for the sample volume of 15 μl. The bacterial suspension from 101 –106 CFU ml−1 was successfully detected with a limit of detection of 10 CFU ml−1 within 10 min using a simplistic detection method.Dr D Bodas and Dr V Gajbhiye acknowledge funding received from ICMR-New Delhi to carry out this work (ICMR Grant No. 5/3/8/12/2019-ITR).Peer reviewe

Sputtered Silicon as a Potential Masking Material for Glass Micromachining – A Feasibility Study

Present paper reports use of sputtered silicon as a masking material for glass micromachining with hydrofluoric acid (HF) as an etchant. A film of sputtered silicon (sp-Si) having thickness of ~1.4 mm was deposited on glass substrate using DC sputtering system. Sp-Si was patterned using standard photolithographic technique. Glass was etched in HF with varying concentration, to estimate masking behavior of sp-Si. Effect of concentration of HF on sp-Si was studied. Etch depth of 460 mm was obtained with dilute HF (20 %) etchant

Creation of a stable hydrophilic poly(dimethyl siloxane) surface by the plasma-induced crosslinking of monomers

International audienceA 3 : 1 composition of functional monomer (FM)-multifunctional acrylate was spin-coated and later crosslinked under the influence of oxygen plasma on the surface of poly(dimethyl siloxane) (PDMS) to generate a surface-anchored crosslinked network bearing functional moieties. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and wetting angle measurements were used to analyze the crosslinked monomer surfaces. Scanning electron microscopy was used to visualize the surface of the film after modification. The results of the surface reconstruction of the FM surfaces and plasma-treated PDMS reveal that long-term hydrophilic surfaces were achieved. Thus, the surface architecture could be favorably manipulated with this remarkable technique with a suitable combination of FMs and crosslinkers

Surface modification and aging studies of addition-curing silicone rubbers by oxygen plasma

International audiencePoly(dimethyl siloxane) (PDMS) has been focused on recently due to its variety of applications specifically in microsystems technology. Many companies market two-component PDMS, which is comprised of a base component and a curing agent. Widely known and used for microsystems applications is Sylgard 184 from Dow Corning. Present work deals with two-component Room Temperature Vulcanized (RTV) PDMS from three different companies. They are Sylgard 184 from Dow Corning, RTV 615 from GE Silicones and RTV 141 from Rhodia Chemicals. Temporary increase in wettability of these three different types of PDMS by oxygen plasma by varying the plasma power and exposure time has been studied and compared with results available in literature. The hydrophobic recovery of the modified surfaces was monitored as a function of time and quantified. The surfaces were characterized using contact angle measurements and ATR-FTIR and XPS spectroscopy, their behavior analyzed in term of free surface energy and work of adhesion