This paper reports on miniaturized hydrogen sensing platforms, exploring several means of fabricating nanostructured films and evaluating their sensing characteristics. Palladium-sputtered nanoporous organosilicate matrices are fabricated using the polymeric system [polymethylsilsesquioxane (PMSSQ); polypropylene glycol (PPG); propylene glycol methyl ether acetate (PGMEA)] followed by volatilization of the liquid phase, i.e., PGMEA and PPG at their boiling points. In order to provide greater adsorption/desorption sites for the test gas, ultra-dense ZnO nano-brushes with very high aspect ratios are successfully fabricated in the porous template. Thereafter, functionalization of ZnO is performed by sputter coating thin Pd films onto the ZnO surface. Intensive characterization for these nanostructures is performed using FESEM, EDAX, FTIR, TEM and AFM techniques. Comparison of all fabricated sensing platforms for hydrogen gas-dependent responses based on temperature, as well as test gas concentrations at various ppm levels, is performed. Palladium coating of ZnO nano-brushes renders this film highly selective to hydrogen and also improves its sensitivity by a factor of ∼66% relative to the uncoated film. Sensitivity to hydrogen is found to be ∼70% and a selectivity test is performed with CO₂ and CH₄, with sensitivities of 5% and 7%, respectively. Pd-functionalized ZnO nano-brushes display enhanced hydrogen response behaviour.

Polymers are widely used in micro-systems for biological detection and sensing and to provide easier alternatives for fabrication of Biomedical Micro-devices (BMMDs). The most widely used polymeric system amenable to micro-fabrication is silicone rubber, particularly poly(dimethylsiloxane) (PDMS). The principal advantage that silicone rubber offers is its ability to get replicated with high aspect ratios by micro-molding. In addition to PDMS, other polymer systems, like resists or epoxies, find extensive use in micro-fabrication providing many aspects such as good interlayer bonding, selective patterning, modified physical properties like variable electrical or optical properties, etc. Most polymer systems are amenable to rapid changes in their surface energies as they are exposed to gas plasmas or UV radiation. Such changes can sometimes be reversible and the exposed surfaces can regain their original configuration with time called hydrophobic recovery. In general, polymer surfaces after such external stimuli become constitutionally highly dynamic and this makes them well suited to prominent applications in fabrication of BMMDs. Our group has extensively worked in the area of polymer surface modification by external stimuli and its characterization and in this paper we have attempted to review some of the group's work.

A novel on-chip inexpensive platform to perform DNA amplification has been fabricated by optimizing the design and microfabrication processes using polydimethyl siloxane (PDMS) and silicon. The silicon base contains a set of microfabricated platinum heater structures on the bottom with a 140-nm-thick spin-on-glass (SOG) layer on the top and a 3 mul replica molded PDMS chamber with feed channels and inlet-outlet ports bonded to this film. The plasma exposed SOG surface is found to undergo recovery of hydrophobicity with time as indicated by an increase in advancing contact angle and bonds very well to another plasma exposed PDMS piece. The bonding protocol developed can be used for a diverse range of substrates, which may form a basis for integration of fluidic assays with microelectronics. The hydrophobic recovery of the microchamber and channels also eliminate the need for various surface passivation techniques for polymerase chain reaction (PCR) chips. A thermal cycler with flexible PCR cycle control is designed and implemented by using a sensing thermocouple. The amplification has been tested using picogram-level template DNA concentration. We have further been able to show negligible nonspecific binding of the template DNA to the hydrophobic interiors of our device by fluorescence measurements and have been able to successfully demonstrate the possibility of multiple usage of this chip without cross-contamination from the previous run

Background: Biofilms occur on a wide variety of surfaces including metals, ceramics, glass etc. and often leads to accumulation of large number of various microorganisms on the surfaces. This biofilm growth is highly undesirable in most cases as biofilms can cause degradation of the instruments and its performance along with contamination of the samples being processed in those systems. The current “offline” biofilm removal methods are effective but labor intensive and generates waste streams that are toxic to be directly disposed. We present here a novel process that uses nano-energetic materials to eliminate biofilms in < 1 second. The process involves spray-coating a thin layer of nano-energetic material on top of the biofilm, allowing it to dry, and igniting the dried coating to incinerate the biofilm. Results: The nanoenergetic material is a mixture of aluminum (Al) nanoparticles dispersed in a THV-220A (fluoropolymer oxidizer) matrix. Upon ignition, the Al nanoparticles react with THV-220A exothermically, producing high temperatures (>2500 K) for an extremely brief period (~100 ms) that destroys the biofilm underneath. However, since the total amount of heat produced is low (~0.1 kJ/cm²), the underlying surface remains undamaged. Surfaces with biofilms of Pseudomonas aeruginosa initially harboring ~ 10⁷ CFU of bacteria /cm² displayed final counts of less than 5 CFU/cm² after being subjected to our process. The byproducts of the process consist only of washable carbonaceous residue and gases, making this process potentially inexpensive due to low toxic-waste disposal costs. Conclusions: This novel method of biofilm removal is currently in the early stage of development. However, it has potential to be used in offline biofilm elimination as a rapid, easy and environmentally friendly method.

Partially aggregated Rhodamine 6G (R6G) dye is used as a lights-on temperature sensor to analyze the spatiotemporal heating of aluminum nanoparticles (Al NPs) embedded within a tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV) fluoropolymer matrix. The embedded Al NPs were photothermally heated using an IR laser, and the fluorescent intensity of the embedded dye was monitored in real time using an optical microscope. A plasmonic grating substrate enhanced the florescence intensity of the dye while increasing the optical resolution and heating rate of Al NPs. The fluorescence intensity was converted to temperature maps via controlled calibration. The experimental temperature profiles were used to determine the Al NP heat generation rate. Partially aggregated R6G dyes, combined with the optical benefits of a plasmonic grating, offered robust temperature sensing with sub-micron spatial resolution and temperature resolution on the order of 0.2 °C.