Novel solutions and applications in the biomedical field could come from exploiting the electroactive properties of conducting polymers towards the development of responsive smart biointerfaces and of flexible, conformable, biocompatible systems. In this sense it is mandatory to control material’s conductivity in situ and this requires the development of suitable patterning processes and the fabrication of individually addressable microelectrodes. Based on the recent introduction by our group of free-standing nanofilms of conductive polymers, the aim of this work was to describe a method for the fabrication of patterned ultra-thin free-standing PEDOT:PSS/Poly (lactic acid) (PLA) bilayer nanosheets. The proposed method involves an ink-jet patterning technique, based on localized overoxidation of PEDOT:PSS by means of a sodium hypochlorite solution. Here we described the fabrication method and characterized the realized nanosheets in terms of their thickness, contact angle, conductivity. The overall process permitted to realize patterned free-standing nanosheets that, despite their low thickness, are very robust and conformable on tissues or on soft and rigid substrates, while allowing for an electrical control of their surface properties. Possible applications are foreseen in the field of conformable electronics, e.g. as electrodes on the brain or smart conductive substrates for cell culturing and stimulation.

Opal particles, with diameter ca. 80 nm, were synthesized by the Stöber method. Samples were exposed to 100 Gy of beta particle irradiation and its thermoluminescence (TL) emission was recorded. TL response presents good reproducibility, standard deviation 1 %. The glow curve displays two TL peaks 86 and 400 °C and the afterglow (AG) phenomenon is observed immediately after irradiation (< 150°C). The synthetic opal-C exhibits a linear dependence of AG response as function of dose from 0.25 to 8 Gy. This dose range is of interest for personal and clinical dosimetry. Moreover, a previous study indicates that cytotoxic and genotoxic effects caused by opal nanoparticles, did not induce unrepairable DNA damage neither a cellular harm. Therefore, our results show synthetic opal-C is a material useful for in vivo radiation dosimetry.

Uric acid biosensor has been developed using tin oxide (SnO2) thin film. The electrochemistry of the developed thin film based electrode is investigated by using cyclic voltammetry. The obtained results demonstrate that the semiconducting SnO2 matrix offers a striking electrocatalytic activity to the immobilized uricase towards the oxidation of uric acid and promotes the transfer of electrons from the active sites of enzyme onto the electrode. SnO2 thin film matrix gives a high sensitivity of 0.2 mA/mM and a shelf life of 20 weeks. Moreover, SnO2 electrode exhibits excellent selectivity and outstanding analytical stability and reproducibility, which enables a reliable and selective determination of uric acid. The SnO2 based uric acid biosensor shows a linear variation in a wide range from 0 to 1.0 mM of uric acid concentration and the Michaelis Menten Constant (Km) is estimated to be 0.28 mM which indicated the high affinity of uricase towards its analyte (uric acid). The results indicate that the SnO2 thin film matrix offers a new and promising platform for the development of novel biosensors.

A large area nanogap electrode fabrication method combinig conventional lithography patterning with the of focused ion beam (FIB) is presented. Lithography and a lift-off process were used to pattern 50 nm thick platinum pads having an area of 300 μm × 300 μm. A range of 30-300 nm wide nanogaps (length from 300 μm to 10 mm ) were then etched using an FIB of Ga+ at an acceleration voltage of 30 kV at various beam currents. An investigation of Ga+ beam current ranging between 1-50 pA was undertaken to optimise the process for the current fabrication method. In this study, we used Monte Carlo simulation to calculate the damage depth in various materials by the Ga+. Calculation of the recoil cascades of the substrate atoms are also presented. The nanogap electrodes fabricated in this study were found to have empty gap resistances exceeding several hundred MΩ. A comparison of the gap length versus electrical resistance on glass substrates is presented. The results thus outline some important issues in low-conductance measurements. The proposed nanogap fabrication method can be extended to various sensor applications, such as chemical sensing, that employ the nanogap platform. This method may be used as a prototype technique for large-scale fabrication due to its simple, fast and reliable features.

Molecular transport as an ageing process in emulsions is revisited using microfluidic droplet production, manipulation and analysis. We show how microfluidic systems provide extremely quantitative insights into the phenomenon. We designed microfluidic systems to address the specificity of molecular transport in fluorinated oils and showed the role of the surfactant solubilised in the oil phase on the time scale of the exchange and rationalize the effect of water soluble additives on the exchange rate. Finally, we also demonstrate that the droplet packing influences the exchange rate through the number of first neighbours.

Zinc oxide (ZnO) thin film deposited onto indium tin oxide (ITO) coated Corning glass substrates using pulsed laser deposition (PLD) technique has been used as a matrix for realization of an efficient urea biosensor after immobilization of urease (Urs) enzyme onto the surface of ZnO. The bioelectrode (Urs/ZnO/ITO/glass) is found to be exhibiting an enhanced sensitivity of 22μΑmΜ−1cm−2 towards urea over a wide detection range of 5-200 mg/dl. The relatively low value of Michaelis menten constant (Km= 0.94mM) indicates high affinity of the immobilized urease towards the analyte (urea). The prepared biosensor retains 90% of its activity for more than 10 weeks. The observed enhanced response characteristics of bioelectrode are attributed to the growth of the matrix (highly c-axis oriented ZnO thin film) with desired surface morphology and high electron communication feature. The results confirm the promising application of PLD grown ZnO thin film as an efficient matrix for urea detection.

Electronic systems are a very good platform for sensing biological signals for fast point-of-care diagnostics or threat detection. One of the solutions is the lab-on-a-chip integrated circuit (IC), which is low cost and high reliability, offering the possibility for label-free detection. In recent years, similar integrated biosensors based on the conventional complementary metal oxide semiconductor (CMOS) technology have been reported. However, post-fabrication processes are essential for all classes of CMOS biochips, requiring biocompatible electrode deposition and circuit encapsulation.

In this work, we present an amorphous silicon (a-Si) thin film transistor (TFT) array based sensing approach, which greatly simplifies the fabrication procedures and even decreases the cost of the biosensor. The device contains several identical sensor pixels with amplifiers to boost the sensitivity. Ring oscillator and logic circuits are also integrated to achieve different measurement methodologies, including electro-analytical methods such as amperometric and cyclic voltammetric modes. The system also supports different operational modes. For example, depending on the required detection arrangement, a sample droplet could be placed on the sensing pads or the device could be immersed into the sample solution for real time in-situ measurement. The entire system is designed and fabricated using a low temperature TFT process that is compatible to plastic substrates. No additional processing is required prior to biological measurement. A Cr/Au double layer is used for the biological-electronic interface. The success of the TFT-based system used in this work will open new avenues for flexible label-free or low-cost disposable biosensors.