I.-A. Pavel, G. Salinas, A. Perro, A. Kuhn
Adv.Intell.Syst. 2020, in press, DOI: 10.1002/aisy.202000217
Miniaturized autonomous swimmers become more and more important in many areas of research, due to various fields of use, ranging from biomedical to environmental tasks. A precise and predictable control of their trajectories is a key ingredient for increasing their application potential. This can be typically achieved by employing external forces such as magnetic or electric fields. An interesting alternative is to use intrinsic features of the swimmers, which allow them to exhibit chemotaxis. Such a built-in “intelligence” enables more complex trajectories, relying on mechanisms which can be considered as very basic analogs of decision-making processes. Herein we present autonomous light-emitting chemo-electronic swimmers, able to navigate along trajectories with increasing complexity. Their decision-making capacities were characterized by recording the light emitted along their path by a fully integrated LED. Chemotaxis was found to be the main driving force behind their behavior, allowing envisioning such systems for solving complex maze patterns.
The combination of bipolar electrochemistry (BE), as a wireless electrochemical approach, and of electrochemiluminescence (ECL) as an imaging readout is a successful strategy with a wide range of analytical applications. However, small conductive entities such as micrometric and nanometric objects are particularly difficult to polarize by BE since they require extremely high electric fields. In order to circumvent this issue due to intrinsic limitations of BE, we elaborated a solid-state micropore, decorated with a rhombus-shaped gold microelectrode. The electric field strength was concentrated inside the solid-state micropore where the conductive gold microelectrode was precisely located and acted as a bipolar light-emitting device. This original configuration allowed achieving adequate polarization of the gold microelectrode in a wireless manner, which led locally to ECL emission. ECL imaging shows that light was generated by the bipolar microelectrode in the center of the micropore. ECL emission could be achieved by imposing a potential value (10 V) to the feeder electrodes that is more than 2 orders of magnitude lower than those required without the micropore. The reported ECL approach opens exciting perspectives for the development of original wireless bioanalytical applications and dynamic bipolar experiments with small objects passing through the pores.
A. Fiorani, D. Han, D. Jiang, D. Fang, F. Paolucci, N. Sojic, G. Valenti
Electrochemiluminescence (ECL) microscopy is an emerging technique with a wide range of imaging applications and unique properties in terms of high spatial resolution, surface confinement and signal-to-noise ratio. Although its successful analytical applications, tuning the depth of field (i.e., thickness of the ECL-emitting layer) is a crucial issue. Indeed, the control of the thickness of this ECL region, which can be considered as an “evanescent” reaction layer limits the development of cell microscopy as well as bioassays. Here we report an original strategy based on chemical lens effects to tune the ECL-emitting layer in the model [Ru(bpy)3]2+/tri-n-propylamine (TPrA) system. It consists of microbeads decorated with the [Ru(bpy)3]2+ labels, classically used in bioassays, and of TPrA as the sacrificial coreactant. In particular we exploit the buffer capacity of the solution to modify the rate of the reactions involved in the ECL generation. For the first time, a precise control of the ECL light distribution is demonstrated by mapping the luminescence reactivity at the level of single micrometric beads. The resulting ECL image is the luminescent signature of the concentration profiles of both diffusing TPrA radicals, which defines the ECL layer. Therefore, our findings provide insights into the ECL mechanism and open new avenues for ECL microscopy and bioassays. Indeed, the reported approach based on chemical lens controls the spatial extension of the “evanescent” ECL-emitting layer and is conceptually similar to evanescent wave microscopy. Thus, it should allow to explore and image different heights in substrates or in cells.
G. Salinas, I.-A. Pavel, N. Sojic, A. Kuhn
Light emitting mobile systems are presented as an important concept for direct visualization and tracking of active objects. Motion or light emission can be achieved by different electrochemical mechanisms. Various devices, that generate light by fluorescence, (electro)chemiluminescence or via light emitting diodes are shown to be an interesting alternative for the detection or release of target molecules, providing straightforward optical imaging. This review summarizes and discusses the recent advances with respect to the design and the potential applications of such original systems.
Improving the sensitivity of plasmonic optical fiber sensors constitutes a major challenge as it could significantly enhance their sensing capabilities for the label-free detection of biomolecular interactions or chemical compounds. While many efforts focus on developing more sensitive structures, we present here how the sensitivity of a sensor can be significantly enhanced by improving the light analysis. Contrary to the common approach where the global intensity of the light coming from the core is averaged, our approach is based on the full analysis of the retro-reflected intensity distribution that evolves with the refractive index of the medium being analyzed. Thanks to this original and simple approach, the refractive index sensitivity of a plasmonic optical fiber sensor used in reflection mode was enhanced by a factor of 25 compared to the standard method. The reported approach opens exciting perspectives for improving the remote detection as well as for developing new sensing strategies.
21 December 2019
18 November 2019
18 November 2019