CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a filing under 35 U.S.C. 371 as the National Stage of International Application No. PCT/EP2018/084237, filed Dec. 10, 2018, entitled “Optical Fiber Based Organic Cantilever with Integrated Transduction,” which claims priority to European Application No. 18162383.6 filed with the Intellectual Property Office of Europe on Mar. 16, 2018 and European Application No. 17306732.3 filed with the Intellectual Property Office of Europe on Dec. 8, 2017, all of which are incorporated herein by reference in their entirety for all purposes.

The present invention relates to the field of organic microelectromechanical sensors based on fiber optics, in particular comprising a through-fiber fabricated cantilever.

The fabrication of polymer tips by means of through-fiber fabrication and the feasibility for sensing applications have already been described.

Through-fiber fabricated cantilever can be analyzed by standard read-out methods such as a vibrometer. Vibrometer enables reliable dynamic studies of a cantilever beam with a frequency resolution of less than 1 Hz. The vibrometer used is a commercial available device and makes the analysis quite straight forward for the user. However, the use of a vibrometer might be inconvenient since the equipment is rather expensive and makes the experimental set-up rather bulky. Furthermore, the analysis of through-fiber fabricated cantilever beams is limited to applications in air or vacuum.

The present invention relates to an integrated read-out scheme for these polymer cantilevers and gives access to new sensing and characterization studies. Therefore, a laser beam is coupled into the optical fiber and guided through the attached cantilever. The emerging light is then collected with appropriate means, for instance with a lens and a 4-quadrant avalanche photodiode. This integrated read-out concept paves the way towards a fully integrated set-up. In this context is the use of the optical fiber especially appealing, since remote operations in particular in harsh environments become accessible.

A first object of the present invention is a sensor device comprising an optical fiber to be coupled with a laser beam, a through-fiber fabricated cantilever onto one end of said optical fiber and having one free end, and a light collector such as a photodiode, characterized in that said through-fiber fabricated cantilever is a patterned cantilever made of a polymer obtained by photo-polymerization of at least one photo-sensitive monomer.

By patterned, it is meant, in the sense of the present invention a fabricated cantilever by photo-structuring (or photo-polymerizing) photo-sensitive monomers.

The through-fiber fabricated cantilever of the sensor device of the invention is thus made of polymer tips and may be used as cantilever beams operated in dynamic or static mode.

The through-fiber fabricated cantilever of the sensor device of the invention preferably presents a length between 10 microns and 200 microns, preferably comprised between 80 and 200 microns.

The through-fiber fabricated cantilever of the sensor device of the invention preferably presents a diameter comprised between 5 and 25 microns, preferably around 10 microns. For instance, the diameter of the through-fiber fabricated cantilever is equal to the core of the optical fiber or is confined by the core of the optical fiber.

The examples of dimensions of the through-fiber fabricated cantilever are non-limitative ones.

The through-fiber fabricated cantilever of the sensor device of the invention may comprise any photopolymerizable material, for instance pentaerythritol triacrylate (PETIA) or a functional polymer, such as molecularly imprinted polymers (MIPs).

In a first embodiment of the invention, at least part of the free end of the through-fiber cantilever of the cantilever sensor device of the invention is treated with a coating chosen among a metal or a polymer.

In a second embodiment of the invention, the free end of the through-fiber cantilever of the cantilevered sensor device of the invention is not treated with a coating allowing the incoming light to be reflected.

Another object of the present invention is a method for the measurement of at least one parameter with the sensor device according to the invention, said method comprising the following steps:

a. Injecting a laser beam into the optical fiber of the sensor device;

b. Measuring the light intensity of the light reflected from the through-fiber fabricated cantilever with a photodiode.

Yet another object of the present invention is a method for the measurement of at least one parameter with the sensor device according to the invention, said method comprising the following steps:

a. Injecting a laser beam into the optical fiber of the sensor device;

b. Collecting the light emerging from (in the sense of transmitted by) the free end of the through-fiber fabricated cantilever, and

c. Analyzing the emerging light (in the sense of collected by) to determine the value of the said at least one parameter.

Examples of parameters that can be measured according to these methods may be temperature, mass, viscosity of liquids, analyte concentrations, and the degree of a polymerization process.

The measurement of these parameters and others can be achieved through measurement of the displacement or deflection, the shift of resonant frequency, or the quality factor of the cantilever, followed by the analysis of the obtained data.

The measurement of at least one parameter according to the invention can be performed either in static mode or in dynamic mode.

The sensor device of the invention may also comprise a plurality of through-fiber cantilevers, optionally made of different material, for instance different polymers. The plurality of through-fiber cantilevers comprises at least two through-fiber cantilevers, preferably at least three, at least four, at least five, more preferably at least ten, and even more preferably at least fifty through-fiber cantilevers. In said embodiment, the plurality of through-fiber fabricated cantilevers may be present on one optical fiber with multiple cores, or on a bundle of optical fibers, the optical fibers may be comprised in the same sheath or jacket.

Online measurements are of great interest for sensing applications and can give access to additional kinetic informations of the binding process of functional polymer materials such as molecularly imprinted polymers (MIPs). Online measurements in liquid media with cantilever sensors are a challenging task due to the viscous damping of surrounding media.

Advantages of presented invention are the miniaturization and/or simplification of the read-out, the possibility of remote operation (for harsh environments or very small samples) and the possibility to operate online measurements in liquid and/or viscous media.

