Electro-optical stimulation/measurement

#The invention relates to dual sensor/actuator systems and more particularly to combination optical and electrical sensor/actuator arrays.

#There is a virtually endless list of applications for devices that can provide stimuli to and/or receive output from and/or detect states of any number of systems, including living beings, machines, chemicals, etc. For example, conductors can deliver energy to systems, such as delivering electricity to a muscle to stimulate contraction of the muscle. Also, conductors can be used to sense electric impulses produced internally to a body to determine when or whether the body has instructed the muscle to contract. Optical fibers can deliver light to systems, e.g., to cause a reaction that can be detected by optical fibers, or other means such as electrical conductors. Beside electrochemical devices, optical fibers and optical fiber bundles allowing simultaneous sensing and imaging have been used increasingly for a variety of different applications.

#As technology advances, there is a push toward smaller, faster, more quickly responsive actuators and sensors. Microelectrodes provide small voltage-drop devices for transferring energy, be it for providing stimuli or measuring electrical output. Microelectrodes are gaining increased importance in electrochemical analysis and sensor technology as their small size leads to small faradaic currents, reduced iR drop and steady-state diffusion currents.

#FIG. 1 is a simplified diagram of an electro-optical system for providing electrical and/or optical stimuli and measuring electrical and/or optical output.

#FIG. 2 is a schematic diagram of an electro-optical array shown in FIG. 1.

#FIG. 3 is a block flow diagram of a process of assembling the array shown in FIG. 2.

#The invention provides novel optoelectric and optoelectrochemical micro-ring arrays and techniques for fabricating such arrays. The arrays include multiple optical fibers coated with electrically conducting material, to serve as microelectrodes disposed about the optical fibers. An exemplary array was fabricated and tested. The array was fabricated by coating individual optical fibers of 25 μm diameter with a 1 μm layer of gold nanoparticles via electroless gold deposition. A self-assembled thiol monolayer (SAM layer) around the individual gold-coated imaging fibers helped prevent electrical contact with neighboring ring-electrodes. To achieve better mechanical stability and to make the device more practical, the electrode/fiber bundle comprising approximately 600 individual gold-coated optical fibers was dipped into epoxy. By polishing the ends of such a device, a ring microelectrode array comprising 600 individual and insulated ring electrodes was formed. To limit diffusional overlap of current, only 20-30% of the micro-ring fiber/electrodes were wired. The inner diameter of the ring electrode is fixed by the diameter of the individual optical fibers (25 μm), while the outer radius is determined by the thickness of the deposited gold. The array was characterized using ferrocyanide in aqueous solution as a model electroactive species to demonstrate that this microelectrode array format exhibits steady state currents at short response times. In addition, cyclic voltammetry experiments were performed using conventional potentiostats due to the amplification of current inherent in the array format. Electrochemiluminescence (ECL) at the ring electrode array was demonstrated through the oxidation of Ru(bpy)32+ in tri-n-propylamide in a pH 7 phosphate buffer solution, where the light generated was collected and detected via the fiber bundle.

#Referring to FIG. 1, a system 10 includes a controller 12, an optical actuator/sensor (A/S) 14, an electrical actuator/sensor (A/S) 16, a processor 18, an electro-optical array 20, and a subject 22. The controller 12 is, e.g., a computer, and is configured to provide control signals to the optical A/S 14 and the electrical A/S 16. These control signals may be in response to information provided to the controller 12 from the A/Ss 14, 16. The processor 18 is configured to obtain information from the A/Ss 14, 16 and process this information into meaningful results for a user of the system 10. The optical A/S 14 includes a charge-coupled device (CCD) camera 15 (see FIG. 2) as the sensor and a light source as the actuator. The actuator portion of the electrical A/S 16 is a potentiostat.

#The potentiostat is a PGSTAT 30 Autolab (made by Eco Chemie of Utrecht, Netherlands). The potentiostat is configured to apply DC voltages to the array 20, e.g., ramping from a lower voltage to a higher voltage and returning to the lower voltage. For example, the potentiostat can apply electricity of voltages starting at 0 V, increasing to 0.6 V, and returning to 0 V, at a rate of 0.02 V/s.