Method and apparatus for determining surface wave data in liquid

Abstract

The present disclosure relates to methods and devices for characterizing interactions between stimuli and liquid films. One aspect of the present disclosure provides a spectral ellipsometry device for characterizing an interaction between a stimulus and a liquid film, the device comprising: a stimulator for providing a stimulus to a liquid film located on a volume of liquid to generate a wave in the liquid film, the liquid film and the volume of liquid having an interface therebetween, the light beam optical assembly is used for irradiating an area of the liquid film with a light beam, the light beam has a first polarization, the light collector is coupled to the detector, the light collector is used for receiving the light beam reflected by the liquid film, and the light beam has a second polarization after being reflected by the liquid film; and a wave measurement module coupled to the light collector and configured to provide surface wave data to characterize the Lucasson wave in the liquid film based on the second polarization.

Description

Technical Field

[0001] The present disclosure relates to methods and apparatus for characterizing the interaction between a stimulus and a liquid film, and more particularly, to methods and apparatus for characterizing such interactions based on the properties of surface waves in a liquid film. Embodiments may employ spectroscopic ellipsometry to observe Lucassen waves. Background Art

[0002] The surface of a material has a thermodynamic potential that is independent of the volume of the material. The physical and chemical properties of the surface arise from the thermodynamic potential of the material. For example, the response of the surface to mechanical perturbations is given by properties such as surface tension and lateral compressibility. Similarly, the response of the surface to electromagnetic perturbations is given by properties such as surface dipole moment. Due to these perturbations, different types of surface waves may be generated on the surface, such as when the surface of a fluid (e.g., a liquid) forms an interface with another fluid (e.g., air). Some example types of surface waves are: Rayleigh waves; gravity waves; capillary waves; Lucassen waves. The physical characteristics of these waves have been described in the literature "Nonlinear fractional waves at elastic interfaces" by Julian Kappler, Shamit Shrivastava, Matthias F. Schneider, and Roland R, published in NetzPhys.Rev.Fluids 2, 114804, November 20, 2017. These waves may be hydrodynamically coupled.

[0003] Rayleigh waves are characterized in that the conceptual fluid particles move in an elliptical motion in a plane perpendicular to the equilibrium plane and parallel to the direction of wave propagation.

[0004] Gravity waves are characterized in that the conceptual fluid particles deviate from the equilibrium position at the surface, where the displacement of the conceptual particle is characterized by a restoring force due to gravity or buoyancy.

[0005] Capillary waves are characterized in that the conceptual fluid particles deviate from the equilibrium position, where the displacement direction of the conceptual fluid particle is transverse to the equilibrium plane and also transverse to the direction of wave propagation, and has a restoring force due to surface tension.

[0006] Lucassen waves are characterized in that the conceptual fluid particles oscillate near the equilibrium position on the surface of the wave medium, the oscillation direction is parallel to the equilibrium plane and also parallel to the direction of wave propagation. In Lucassen waves, the conceptual particle is subjected to a restoring force that originates from the surface elastic modulus of the wave medium. In other words, Lucassen waves are compression-rarefaction waves that occur in the boundary (interface) plane between the wave medium and an adjacent medium (such as air).

[0007] Lucassen waves have been observed in lipid monolayers and other types of liquid systems.

[0008] Shamit Shrivastava, Matthias F. Schneider Opto-Mechanical Coupling in Interfaces under Static and Propagative Conditions and Its Biological Implications describes how to generate waves in lipid monolayers with a dipping needle by mechanical means and how to measure the parameters of the generated waves, e.g., measuring the intensity of fluorescent particles in the generated waves and the lateral pressure of surface waves using a photodetector and a Wilhelmy balance, respectively.

[0009] Shrivastava S, Schneider MF. 2014 Evidence for two-dimensional solitary sound waves in a lipid controlled interface and its implications for biological signalling. J.R.Soc.Interface 11:20140098 describes a method for generating Lucassen waves in lipid monolayers and how to measure the parameters of the wave (e.g., fluorescence energy transfer (FRET) measurements; piezo cantilever). This document also describes how to characterize the state of the lipid monolayer through various film parameters (e.g., surface density of lipid molecules, temperature, pH value, lipid type, ion or protein adsorption, solvent embedding, etc.) and how the state of the lipid monolayer affects the parameters of the waves propagating in the lipid monolayer.

[0010] Bernhard Fichtl, Shamit Shrivastava & Matthias F. Schneider, Protons at the speed of sound: Predicting specific biological signaling from physics Nature Scientific Reports describes how to generate Lucassen waves in lipid interfaces in response to changes in the system pH value and that the speed of these waves can be controlled by the compressibility of the interface. This document describes how the parameters of these waves vary with the degree of change in the pH value. This document also describes how to measure the mechanical and electrical changes in the lipid interface (e.g., using a Kelvin probe).

[0011] The Lucas wave can be described as an interfacial compression wave and can be regarded as a two-dimensional acoustic wave (an acoustic wave restricted to the surface forming the boundary between two phases, such as the fluid-air boundary). Similar to acoustic waves, shock waves may also exist in the Lucas wave system (e.g., two-dimensional shock waves). The Lucas shock wave can be characterized in the same way as the Lucas wave, but with the additional restriction that the change in the wave medium is non-linear and / or discontinuous.

[0012] S. Shrivastava, Shock and detonation waves at an interface and the collision of action potentials, Progress in Biophysics and Molecular Biology describes how Lucas shock waves propagate through a lipid interface.

[0013] WO2019234437A1 describes how to utilize a lipid interface to transmit and receive signals. This document describes a signal processing device, including: a first medium; a second medium; a lipid interface disposed between the first medium and the second medium, where the lipid interface includes a plurality of lipid molecules; an input transducer for applying an input signal to the lipid interface, where the input signal is set to generate a mechanical pulse in the lipid interface; and an output transducer for receiving an output signal by detecting a mechanical response caused by the mechanical pulse generated by the input transducer in the lipid interface; where the lipid interface is set to propagate the mechanical pulse from the input transducer through the lipid interface to the output transducer. Summary of the Invention

[0014] Aspects of the present invention are listed in the independent claims, and optional features are listed in the dependent claims. The aspects of the present invention can be provided in combination, and the features of one aspect can be applied to other aspects.

[0015] One aspect of the present invention provides a spectroscopic ellipsometry device for characterizing the interaction between a stimulant and a liquid film, the device including: A stimulator for providing a stimulant to a liquid film located on a certain volume of liquid to generate waves in the liquid film, with an interface between the liquid film and the certain volume of liquid, A beam optical assembly for irradiating an area of the liquid film with a beam having a first polarization, and a light collector coupled to a detector, the light collector for receiving the beam reflected by the liquid film, the beam having a second polarization after being reflected by the liquid film; A wave measurement module, coupled to an optical collector and operative to determine surface wave data to characterize waves in a liquid film based on a second polarization.

[0016] Waves in the liquid film can include multiple wave modes, such as surface wave modes. For example, the multiple wave modes can include at least one of Lucassen waves, capillary waves, gravity waves, and Rayleigh waves.

[0017] The surface wave data may include sufficient degrees of freedom to provide an overdetermined representation of the surface wave, with one wave mode being Lucassen waves. Other information may also be obtained from the surface wave data. The surface wave data may include a waveform, e.g., a sequence of samples defining a time-varying signal that includes characteristics such as amplitude, arrival time, frequency, and phase. The contributions of measuring these aspects of the signal may include contributions from different wave modes present (including Lucassen waves). This enables the extraction of feature vectors from the surface wave data to define features such as Lucassen waves. As long as the underlying physical measurements are sensitive to such effects, making them present in the data and determinable from the data (sufficiently represented by the data), it is not necessary to actually extract features that explicitly define these or other wave modes. The apparatus and methods of the present disclosure can make Lucassen wave mode information / effects present and determinable in the surface wave data by using ellipsometric techniques.

[0018] The surface wave data can be based on: the s-polarization component of the second polarization and the p-polarization component of the second polarization. For example, the surface wave data can include an indication of the SP ratio.

[0019] The surface wave data can indicate a change in the polarization state from a first polarization to a second polarization. This can indicate how the polarization direction is changed by reflection from the liquid film and / or how the polarization distribution is changed by that reflection.

[0020] The surface wave data can include a first time series of samples collected from the liquid film, and the wave measurement module can be operative to provide a second time series based on the first time series, where the sampling rate of the second time series is lower than that of the first time series. The sampling rate of the second time series can be at least 2 kHz, e.g., at least 10 kHz.

[0021] The second sampling rate can be selected based on the size of the region.

[0022] The light beam can include a coherent light beam, such as a laser. The laser can have a polarization direction, and the beam optical assembly can be configured to rotate the polarization direction such that the laser is aligned with the p-polarization axis at the surface of the film, e.g., its surface.

[0023] The beam optical assembly can be configured to focus the light beam, e.g., to provide a focus of the light beam that is positioned such that the light beam is non-collimated (e.g., diverging or converging) when it encounters the optical collector.

[0024] The liquid film may comprise at least one of a protein and a lipid. The light beam may comprise a wavelength selected according to the composition of the film. The light beam may be provided to the surface at an angle of incidence selected according to the composition of the film.

[0025] The stimulator may comprise a test substance provider for contacting the surface of the liquid with a test substance so as to provide a stimulus.

[0026] The stimulator may be used to provide an electrical stimulus to the film.

[0027] The operation of the light collector may be coupled to the operation of the stimulator such that surface wave data may be determined at a selected time after the stimulus, for example, the time may be selected based on the location of the stimulus on the surface.

[0028] The stimulus may generate multiple wave modes in the liquid film, such as surface wave modes. For example, in addition to including Lucas waves, the multiple wave modes may include at least one of capillary waves, gravity waves, and Rayleigh waves.

[0029] One aspect of the present invention provides a method comprising: providing a stimulus to a liquid film located on a volume of liquid to generate waves in the liquid film, there being an interface between the liquid film and the volume of liquid, irradiating a region of the liquid film with a light beam having a first polarization, and receiving the light beam after reflection from the liquid film, the light beam having a second polarization after reflection from the liquid film; determining surface wave data based on the received light beam to characterize Lucas waves in the liquid film based on the second polarization.

[0030] The surface wave data may be based on: the s-polarization component of the second polarization and the p-polarization component of the second polarization. For example, the surface wave data may include an indication of the SP ratio of the light beam after reflection from the liquid film.

[0031] The size of the region may be defined by the light beam size of the liquid film and the radius may be less than 5 mm, such as less than 1 mm.

[0032] The method may include focusing the light beam to provide the light beam size and / or such that the light beam is non-collimated (e.g., convergent or divergent) when it reaches the light collector.

[0033] When there is a viscoelastic film on the liquid surface, multiple surface wave modes constrained by different physical mechanisms and time scales may coexist and propagate together. Embodiments of the present disclosure may address the problem of how to resolve the information contained in such waves.

[0034] Some embodiments use the interaction of polarized light incident on a liquid film at multiple angles and / or multiple wavelengths. This can provide an overdetermined system such that wave modes that might otherwise be difficult or impossible to characterize can be fully determined. Using multiple angles and / or multiple wavelengths enables the information present in the dynamic surface modes to be acquired more quickly (e.g., acquired in parallel from measurements at a single interaction point between the film and the light illumination).

[0035] Any feature of any one example disclosed herein can be combined with any selected feature in other examples described herein. For example, features of a method can be implemented in appropriately configured hardware, and the specific hardware configurations described herein can also be used for methods implemented by other hardware. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the present disclosure will now be described by way of example only with reference to the accompanying drawings, in which:

[0037] Figure 1 is a functional block diagram of an apparatus according to the present disclosure;

[0038] Figure 2 is a flowchart of a method of operating an apparatus as Figure 1 described; and

[0039] Figure 3 is a functional block diagram of an apparatus as Figure 1 shown;

[0040] Figure 4A is a schematic diagram of a reservoir computing unit;

[0041] Figure 4B is a simplified top view schematic diagram of a reservoir computing unit having two input terminals;

[0042] Figure 5 is a schematic diagram of a first reservoir computing unit coupled to a second reservoir computing unit;

[0043] Figure 6 is a schematic diagram of a network of reservoir computing units.

[0044] In the drawings, like reference numerals denote like elements. DETAILED DESCRIPTION

[0045] Figure 1A spectroscopic ellipsometry apparatus 1 for characterizing the interaction between a stimulus and a liquid film 3 is shown. The apparatus characterizes the Lucassen waves 5 in the liquid film 3 based on the polarization of the reflected light beam 7. In particular, the apparatus can sense changes in the refractive index (and thus density) of the liquid film 3 using the ratio between the s-polarization component and the p-polarization component of the reflected light beam 7. A time series of such data can be used to characterize the Lucassen waves 5 without using labels in so-called "Förster" or fluorescence resonance energy transfer (FRET) techniques.

[0046] Figure 1 The apparatus 1 shown includes a stimulator 9, a beam optical assembly 11, a light collector 13, a detector 15, and a wave measurement module 17. As Figure 1 shown, the apparatus 1 also includes a reservoir 23 that holds a volume of liquid 21 and forms a liquid film 3 on the surface of the liquid 21. The reservoir 23 can be provided by a trough, such as a Langmuir trough.

[0047] Figure 1 Also shown are mechanical fixing devices 19 for fixing the apparatus in a relative position with respect to the reservoir 23. It should be noted, however, that these fixing devices 19 are not essential and can be manufactured and sold separately from the apparatus 1 itself. The wave measurement module 17 is connected to the stimulator 9 and the detector 15 for controlling the communication of signals and data. The wave measurement module 17 can also be connected to the beam optical assembly 11.

[0048] Generally, the film 3 includes a liquid of a different type than the volume of liquid 21. Thus, an interface, such as a liquid-liquid interface, can exist between the liquid film 3 and the volume of liquid 21. The film 3 can have viscoelastic properties. These films and other types of films can exhibit various surface wave modes in response to a stimulus. Examples of such wave modes include Rayleigh waves, gravity waves, capillary waves, and Lucassen waves.

[0049] Examples of liquid types that provide the film 3 include proteins and lipids, as well as other types of liquids. It should be understood that in the context of the present disclosure, such materials can also be (e.g., dispersed in a suspension or otherwise) maintained in a volume of liquid, and a dynamic equilibrium can exist between the film and the materials maintained in the volume of liquid 21. Examples of liquid types that can provide the volume of liquid 21 include aqueous solutions.

[0050] The beam optical assembly 11 includes a polarized light source for irradiating a region of the liquid film 3 with a beam 7 at a selected incident angle α. The beam 7 can also be coherent light. Examples of suitable light sources include lasers, and the beam optical assembly can include a polarizer.

[0051] The light collector 13 is for receiving the beam 7 after reflection from the region of the film and supplying the reflected beam to the detector. The position of the light collector 13 is set such that the optical axis of the light collector 13 points at the region of the film 3 at the specular reflection angle α, which is the specular reflection angle at which the beam emitted by the beam optical assembly is incident on the film.

[0052] The detector 15 is for sensing the parameters of the light received from the light collector 13 and supplying a signal including these parameters to the wave measurement module 17. Typically, these parameters include the polarization of the beam 7. For example, these parameters can include intensity measurements of one or more polarization components of the received light, such as: (a) the intensity of a first component of a second polarization and / or (b) the intensity of a second component of a second polarization. The second component can be orthogonal to the first component. The first component can be the s-component and the second component can be the p-component.

[0053] The stimulator 9 is positioned relative to the film 3 such that the stimulator 9 can apply a stimulus to the film 3. For example, the stimulator 9 can include a source of a test substance and is for contacting the surface of the film 3 with the test substance to provide a stimulus. Such a stimulus can generate waves 5 in the liquid film 3, and the waves 5 exhibit some or all of the above wave patterns.

[0054] The wave measurement module 17 is for controlling the stimulator 9 to apply a stimulus to the film 3 and operating the detector 15 to collect time series samples of the light received at the detector 15. These samples can include intensity samples of one or more of the above polarization components. Typically, the sampling rate is at least 1 MHz, such as 10 MHz. The wave measurement module can also be used to apply a low-pass filter to the time series before downsampling the data to approximately 20 kHz. Typically, the sampling rate of the downsampled time series is selected according to the size of the irradiated region and the expected speed of the waves in the film. For example, the expected speed may be about 1 ms -1 , and the diameter of the irradiated region may be about 5 mm. In this case, the upper limit of the frequency at which surface waves can be meaningfully sampled will be 10 kHz. The sampling rate of the downsampled time series can be selected to ensure that the measurement remains within this available bandwidth.

[0055] The wave measurement module 17 can be used to control the sampling time of these samples based on the operation of the stimulator 9. For example, such that the surface waves 5 in the region of the thin film irradiated by the light beam 7 can be sampled at a selected time point and for a selected duration after stimulation. Generally, the above time point and / or duration are selected based on the distance from the portion of the thin film 3 where the stimulation is applied to the irradiated region. The wave measurement module can also be used to provide a specific sampling scheme for a specific measurement type. The wave measurement module can be used to implement a first sampling scheme to perform a first measurement type and implement a second different sampling scheme to perform a second different measurement type. For example, to measure the viscosity or hydrophobicity of a lipid thin film, or to measure the binding in a protein thin film, the wave measurement module can use a longer sampling duration (total time of collecting samples). The recording of a single stimulation typically has a time resolution on the order of microseconds and a duration on the order of seconds. This may be sufficient for measuring the properties of molecules that interact strongly and / or rapidly with the thin film (such as electrostatic interactions or hydrogen bonds). In some embodiments, observing multiple stimulations at a repetition frequency of several seconds over several minutes to several hours can better measure the properties of molecules that interact weakly and / or slowly with the thin film (such as binding or reaction kinetics).

[0056] In other modes, the wave measurement module can be used to sample data within a selected time interval after the thin film is stimulated and repeat the same sampling within the same time interval after subsequent stimulations to provide repeated measurements. The duration of these measurements may be relatively short.

[0057] In operation, the wave measurement module 17 operates the stimulator 9 to apply a stimulation to the thin film 3. This triggers the surface waves 5 in the thin film 3. The waves propagate outward from the position where the stimulation is applied on the thin film. The light beam optical assembly 11 irradiates the region of the thin film, and the wave measurement module 17 operates the detector 15 to collect a sequence of samples of the reflected light beam 7, where the reflected light beam 7 is reflected by this region and provided to the detector 15 by the light collector 13.

[0058] Thus, the change in the perturbation of the thin film 3 at this position over time can be recorded through the sequence of data samples (time series). Each sample in the time series can include polarization data, and these data can be in the form of the intensity of the s polarization component and the intensity of the p polarization component of the reflected light. The wave measurement module 17 can be used to determine an indication of the polarization angle of the reflected light beam 7, such as the ratio of the intensity of the s component to the intensity of the p component for each sample. The wave measurement module can extract the characteristics of the Lucassen waves from this time series. For example, examples of the characteristics of the Lucassen waves include its amplitude, frequency content, phase velocity, group velocity, phase, etc. Then, the wave measurement module 17 can use these characteristics of the Lucassen waves to provide information about the stimulation or the thin film, as described below.

[0059] In the context of the present disclosure, it is understood that the polarization change caused by thin film reflection is related to the refractive index of the thin film. The current inventors recognize that in a thin film, the refractive index is also related to the density of the thin film. Thus, the wave measurement module can derive information on the change in thin film density over time from a time series of samples (such as the s-p ratio). This may enable the characterization of Rayleigh waves without the use of labels such as in the FRET method.

[0060] Figure 2 A method 100 of operating a device such as Figure 1 shown is presented to characterize Rayleigh waves in a liquid thin film. These methods can also be used to characterize stimuli as described below.

[0061] Figure 2 The method shown includes providing a stimulus to a liquid thin film 3 located on a volume of liquid 21 to generate a wave 5 in the liquid thin film 3. The stimulus can be a chemical stimulus, for example, by applying a drop of a test substance to the thin film 3.

[0062] The stimulus causes a wave 5 in the thin film that propagates in the thin film 3 until it reaches a region of the liquid thin film that is illuminated 104 by a light beam 7.

[0063] Typically, the light beam 7 has a defined polarization before being reflected by the thin film 3. The light beam can be focused such that the focus of the light beam 7 is between the light source and the thin film or between the thin film and the detector. In these embodiments, the light beam illuminating the thin film is non-collimated (e.g., diverging or converging), which may provide a range of different angles of incidence over the region. This may help reduce signal intensity fluctuations caused by wave-induced thin film deformation (vertical displacement) and / or unwanted interference effects in the light collection optics.

[0064] A light sample reflected from the illuminated region is collected 106 and the polarization of the reflected light 7 is determined 108 from these samples. This can be done with reference to the initial polarization of the light beam 7 (e.g., before being reflected by the thin film 3). One way is to polarize the light beam (e.g., a polarizer inserted between the light source and the thin film can be used to polarize the light beam). The polarization change can be determined based on the intensity of the s-polarization component of the reflected light beam and the intensity of the p-polarization component of the second polarization. For example, the s-p ratio can be used. Thus, the polarization change of the light beam caused by thin film reflection can be determined for each sample in the time series. The time series can be filtered and downsampled as described above. This provides a method of characterizing 110 Rayleigh waves in a liquid thin film 3 by using a time series of polarization changes measured on the light beam.

[0065] A wave measurement module 17 or other processing device can determine 112 the characteristics of the Rayleigh wave from these data, which include its amplitude, frequency content, phase velocity, group velocity, phase, etc.

[0066] This has many technical uses.

[0067] As a first example, this can provide a method for characterizing a stimulus. To this end, a wave measurement module or other processing device can compare the characteristics of the Lucas waves caused by the stimulus to be characterized with the same characteristics of the Lucas waves caused by other stimuli (such as known or reference stimuli). The stimulus under discussion can be a chemical stimulus, which can be provided by contacting the thin film with a test substance (such as a droplet containing the test substance). The characteristics of the Lucas waves generated by the known thin film under this stimulus can be compared with the characteristics of the Lucas waves generated by the same thin film under a known chemical stimulus (such as the stimulus of a known or reference substance). This can be used to indicate whether a substance of interest is present in the test substance, and / or to provide a method for characterizing the test substance itself.

[0068] As a second example, this can provide a method for characterizing materials in a thin film. To this end, a wave measurement module or other processing device can compare (a) the characteristics of the Lucas waves obtained when a thin film containing the material responds to a known stimulus with (b) the characteristics of the Lucas waves obtained when a reference thin film (such as a thin film without the material or other reference thin film) responds to the same stimulus. In this example, the stimulus can be a chemical stimulus, such as a droplet of a known substance, or an electrical stimulus, such as a test signal in the form of a voltage pulse of a known form. In this example, the characteristics of the Lucas waves generated by a thin film containing a specific component (such as a lipid or protein thin film containing a test substance) under this stimulus can be compared with the characteristics of the Lucas waves generated by a different thin film (such as a thin film containing at least one different component, such as a lipid or protein thin film without the test substance or containing a different dopant) under the same stimulus. This can provide a method for characterizing the test substance, and / or a method for detecting whether the test substance is present in the lipid, and / or a method for determining the similarity measure between test substances.

[0069] The above comparison can be carried out by any suitable method. For example, a wave measurement module or other processing device can be used to provide a data vector containing the first Lucas wave characteristics and determine the "distance" from the vector of the first Lucas wave to the vector of the second Lucas wave in the vector space defined by the characteristic vector. This distance can be the Euclidean distance.

[0070] In the context of the present disclosure, those skilled in the art will understand that the Figure 1 and Figure 2 methods and devices explained can be implemented in a variety of different ways. One possible implementation is as Figure 3 shown.

[0071] Figure 3 Shows a spectroscopic ellipsometry device 1', which device 1' is associated with Figure 1The device described in

[0072] is the same, but the beam optical assembly 11, the light collector 13, and the detector 15 therein are implemented in a specific manner. Figure 3 In the illustrated embodiment, the beam optical assembly 11' includes an optical chain that sequentially includes: a laser 4 that provides a coherent light source, an optical lens module 6 for adjusting the beam profile, a wave plate 8, and a linear polarizer 10.

[0073] Generally, the optical lens module 6 includes one or more beam adjustment elements, such as lenses, which are used to modify the profile of the laser beam passing through the module. Figure 3 The optical lens module 6 in the illustrated embodiment is used to provide a Gaussian beam profile, but other profiles can also be used. The optical lens module 6 can include a focusing element, such as a lens, configured such that the beam passing through the module converges at a focal point that is located before the beam reaches the thin film.

[0074] Generally, a laser beam has a natural polarization in a specific direction - typically the ratio of the polarization components is about 1000:1. The wave plate 8 is a half-wave plate and is used to shift one polarization component of the laser by n(180°) relative to its orthogonal component. This can rotate the polarization of the light from the laser so that the main polarization component of the laser is aligned with the P polarization axis of the liquid surface in the reservoir 23. The beam adjusted by the wave plate is then provided to the linear polarizer 10, and the linear polarizer 10 blocks the light that is not polarized in alignment with the polarizer from passing through. Using the wave plate 8 and the linear polarizer 10 in sequence can provide linear polarization without excessive attenuation.

[0075] As Figure 3 shown, the optical chain in the light collector includes a laser line filter 18, followed by a polarization beam splitter 16, and then two separate intensity detection elements 15-1 and 15-2. Among them, the first intensity detection element 15-1 is located after the polarization beam splitter 16 and is used to receive the light passing through the beam splitter 16, and the other intensity detection element 15-2 is placed to receive the light reflected by the beam splitter 16.

[0076] The laser line filter 18 can reduce the ambient light intensity entering the light collection optical assembly, thereby improving the signal-to-noise ratio (SNR).

[0077] The first detection element 15-1 and the second detection element 15-2 each include a light intensity detector connected to a wave measurement module 17, which is used to provide respective light intensity signals to the light intensity detector, and the above light intensity signals indicate the intensity of the light incident on each corresponding detection element 15-1, 15-2.

[0078] In the operation of the device, the laser 4 generates a light beam 7, and the optical lens module 6 adjusts the light beam 7 so that the profile of the light beam 7 is Gaussian. The lens module 6 also focuses the light beam 7, making the light beam 7 non-collimated, and provides a selected beam diameter at the thin film 3. For example, the lens module 6 can be used to make the diameter of the incident point of the light beam on the thin film less than 5 mm, for example less than 2 mm.

[0079] The light beam 7 passes through the wave plate 8, and the wave plate 8 delays one polarization component of the light beam 7 by n(180°) so that the polarization direction of the light beam is aligned with the P polarization axis of the thin film. The light beam 7 is then provided from the wave plate 8 to the linear polarizer 10, and the linear polarizer 10 blocks the light that is not aligned with the polarization direction of the polarizer. The polarized light beam passing through the polarizer 10 then impinges on the thin film 3. The beam optical assembly can be used to make the incident angle α of the light beam 7 on the thin film 3 the Brewster angle. Since the beam optical assembly can be configured to provide a non-collimated light beam, the light beam 7 may be convergent or divergent when it contacts the thin film. In this way, a light beam can provide a series of incident angles. This may have special advantages for wave imaging in / on a liquid thin film.

[0080] The light beam 7 is then reflected by the thin film to the beam collector. The polarization of the light beam changes after being reflected by the thin film. The magnitude of this change depends on factors such as the refractive index of the thin film, and the refractive index depends on the density of the thin film. Therefore, it can be understood that the polarization of the reflected light beam may be different from that of the incident light beam.

[0081] The reflected light beam whose polarization is changed due to reflection then reaches the beam splitter 16 through the laser line filter of the light collector. The beam splitter 16 reflects the polarization component orthogonal to its polarization axis in the light beam to the first detection element, and transmits the component parallel to its polarization axis to the second detection element.

[0082] The detection elements 15-1 and 15-2 respectively provide signals indicating the intensity of the incident light to the wave measurement module 17.

[0083] The wave measurement module 17 then samples the intensity signals from the two detection elements at a first sampling rate (such as 1 MHz or higher) to provide a first time series. The wave measurement module applies a low-pass filter to this time series, and then down-samples the filtered time series to provide a second time series with a second sampling rate. The cut-off frequency of the low-pass filter can be selected according to the Nyquist criterion of the second sampling rate (for example, making the second sampling rate at least twice the cut-off frequency of the low-pass filter). The signals from the first detection element and / or the second detection element can then be used to indicate the polarization angle of the reflected light beam. This can be used to determine the degree of polarization rotation caused by thin film reflection (for example, referring to the polarization of the light beam provided by the beam optical assembly). For example, the ratio of the two polarization components can be used to indicate the polarization angle of the reflected light beam.

[0084] Thus, any wave caused by the applied stimulus propagates through the film 3 to the region irradiated by the laser beam 7. Subsequently, the change in the film density in this region can be detected by the wave measurement module as a change in the polarization angle of the reflected beam, and these changes can be observed in the time series of the (optionally filtered and downsampled) samples obtained from the irradiated region. These data provide an indication of the perturbation of the film density over time, enabling the observation of the Lukaszewicz wave. This allows the parameters of the Lukaszewicz wave to be measured, such as its phase, amplitude, frequency content, phase velocity, group velocity, etc. Embodiments allow the measurement of the change in the polarization vector upon reflection, such as the change in the polarization direction and the change in the polarization distribution, such as the degree to which a highly polarized beam becomes less polarized after interaction.

[0085] Further embodiments are contemplated. It should be understood that any feature described in relation to any one embodiment can be used alone, or in combination with other described features, or in combination with one or more features of any other embodiment, or in combination with any combination of any other embodiment. Additionally, equivalents and modifications not described above can also be used without departing from the scope of the present invention.

[0086] For example, the measure of the change in the polarization angle can be determined by measuring the change in one component caused by reflection and providing some adjustment to compensate for the attenuation of the beam, without measuring both components. The signal can be filtered and downsampled before determining the polarization angle of the reflected beam, or the polarization angle can be determined first. In some embodiments, the two polarization signals can be combined in the analog domain before digitization.

[0087] Reference Figure 3 The described laser line filter can be provided by any suitable optical filter, such as a bandpass filter. The passband of such a filter can be selected based on the wavelength of the light source used in the beam optics. In some embodiments, a bandstop filter can be used, and the stopband of the bandstop filter is selected to attenuate the most common ambient light sources.

[0088] Although Figure 3 a waveplate is described as an option in the device of , other methods of changing the polarization state of light can also be used - for example, any method that delays (or lags) one polarization component relative to its orthogonal component. One alternative to the traditional crystalline quartz waveplate is a polymer retardation film. The manner of changing the polarization state of light can be achromatic.

[0089] It can be understood that Figure 3 the light collector of the shown device can be used for Figure 1 the device of Figure 1 the light collector of the shown device can also be used for Figure 3 the device of

[0090] The physical systems described herein can be used for reservoir computing. For example, if an input signal is used to provide a stimulus and the output signal is derived from surface wave data, it can be seen that the spectroscopic ellipsometry device of the present disclosure provides a data operation that converts the input signal into the output signal.

[0091] Similarly, a reservoir computing unit can be used to apply a transformation to the input signal, thereby generating an output signal. The relationship between the output signal and the input signal corresponds to the transformation applied by the reservoir computing unit to the input signal. Accordingly, embodiments of the present disclosure provide a reservoir computing unit that includes the spectroscopic ellipsometry device of the present disclosure, wherein the stimulator provides a stimulus based on the input signal (e.g., a stimulus encoding the information carried by the input signal). The reservoir computing unit provides an output signal based on the wave data generated by the stimulus. Two or more such reservoir computing units can be connected together to form a network, and each unit can perform different data operations. In certain embodiments, the stimulator can be used to apply stimuli corresponding to two or more input signals. These stimuli can be applied to the liquid separately and independently of each other so that the corresponding wave data encodes information corresponding to the combination of these signals.

[0092] Thus, it can be seen that in such a unit, the output signal may depend on the input signal (or input signals) in a non-linear manner. The relevant function that converts the input signal (or input signals) into the output signal may correspond to or represent the data operation performed by the reservoir computing unit.

[0093] Figure 4A is a schematic diagram of an exemplary reservoir computing unit 400. The reservoir computing unit includes: an input terminal 410; a reservoir 420 for containing a liquid 30; a spectroscopic ellipsometry device 430; and an output terminal 440.

[0094] As described elsewhere herein, the spectroscopic ellipsometry device 430 includes: a stimulator 431 for providing a stimulus to the liquid 30 to generate a response (e.g., waves on the surface of the liquid); a beam optical assembly ( Figure 4A not shown in the figure) for irradiating a region of the liquid 30 with a beam having a first polarization; and a light collector ( Figure 4A not shown in the figure) coupled to a detector, the light collector for receiving the beam reflected from the surface, the beam having a second polarization after reflection; a wave measurement module ( Figure 4A not shown in the figure) coupled to the light collector, the wave measurement module for providing surface wave data based on the second polarization; an output terminal 440 for providing an output signal based on the surface wave data.

[0095] The beam optical component, the light collector, and the wave measurement module can be described as measurement components and are schematically shown as element 433 in Figure 4A as shown.

[0096] The input terminal 410 is used to receive an input signal. The input signal can be an electrical signal encoding data. The input terminal 410 is used to provide the input signal to a stimulator that provides a stimulus to the liquid 30 contained in the reservoir 420. The stimulus provided by the input terminal 410 generates a response 50 in the liquid 30. The response 50 can be one or more mechanical waves in and / or on the liquid, and these mechanical waves can include various wave modes such as, for example, Rayleigh waves.

[0097] The stimulator 431 of the spectroscopic ellipsometry device 430 is used to provide a stimulus to the liquid 30 contained in the reservoir 420. The stimulator can be any stimulator described herein.

[0098] The stimulator can be used to provide an electrical stimulus to the liquid. The stimulator can include a pair of electrodes and a voltage provider, where the voltage provider is used to provide a voltage (such as an alternating voltage) between the electrodes. The electrodes can be used to provide a voltage difference in a direction parallel to the liquid surface (for example, the stimulator can include an interdigitated transducer (IDT)) or in a direction perpendicular to (such as through) the liquid surface.

[0099] The reservoir 420 contains the liquid 30. The liquid 30 is used to receive the stimulus (from the stimulator 431) based on the input signal from the input terminal 410. As described above, the stimulus applied to the liquid generates a response 50 in the form of a mechanical wave. Optionally, a thin film can be provided on the liquid surface.

[0100] The spectroscopic ellipsometry device 430 is used to measure the response 50 of the liquid 30 in the reservoir 420 to the stimulus based on the input signal. In particular, as described above, the measurement component 433 (i.e., the beam optical component, the light collector, and the wave measurement module of the spectroscopic ellipsometry device 430) is used to measure the response 50 and provide surface wave data.

[0101] The output terminal 440 is used to provide an output signal based on the surface wave data (i.e., measured by the measurement component 433). The output signal depends non-linearly on the input signal, and the function associated with converting the input signal into the output signal corresponds to or represents a data operation, where the data operation is performed by the reservoir computing unit on the input signal.

[0102] The reservoir computing unit 400 is configured to convert an input signal into an output signal. This conversion may depend on any of the following factors: the properties of the liquid 30 in the reservoir (e.g., a liquid containing a thin film); the thermodynamic parameters of the liquid and / or the thin film (e.g., the temperature of the liquid); the specific depth of the liquid. The reservoir computing unit may be arranged such that the conversion performed by the unit can be controlled by changing one or more such parameters.

[0103] In operation, an input signal is provided to the input terminal 410. The input signal encodes data or information, for example, in the form of a time-varying waveform. The stimulator 431 provides a stimulus to the liquid 30 that indicates the input signal from the input terminal 410.

[0104] The stimulus induces a response 50 in the liquid 30. As described above, the response 50 may be one or more mechanical waves. The response 50 is based on the input signal and the configuration of the reservoir computing system 400. The response 50 is measured by the measurement component 433 of the spectroscopic ellipsometry device 430 to obtain surface wave data in the manner described herein.

[0105] The output terminal 440 provides an output signal indicative of the surface wave data.

[0106] Figure 4B is a simplified top view schematic of the reservoir computing unit 401, which has two input terminals 411 and 412. The reservoir computing unit 401 is different from the reservoir computing unit Figure 4A in that the unit 401 has two input terminals, namely a first input terminal 411 connected to the first stimulator 431 and a second input terminal 412 connected to the second stimulator 432. The unit 401 can be used to provide two corresponding stimuli to the liquid based on two input signals, thereby generating a response in the liquid. The response will be based on the two input signals, and thus the output signal based on the response will also be based on the two input signals. By applying two stimuli, the unit can combine the two inputs.

[0107] Figure 5 is a schematic diagram of the first reservoir computing system 500 that includes a plurality of reservoir computing units. In this example, the first unit 400-1 is connected in series with the second unit 400-2, that is, the output terminal 440-1 of the first unit 400-1 is connected to the input terminal 410-2 of the second unit 400-2.

[0108] As Figure 5 shown, both the first reservoir computing unit 400-1 and the second reservoir computing unit 400-2 can be provided by the reservoir computing unit as described above with reference to Figure 4A the foregoing.

[0109] Figure 5There is shown a series arrangement of reservoir computing units for performing a series of transformations on an initial input signal (i.e., the input signal provided to the first reservoir computing unit in the series) to provide a final output signal (i.e., the output signal provided by the last reservoir computing unit in the series), which is the result of a series of operations on the initial input signal.

[0110] Figure 6 is a schematic diagram of a second reservoir computing system 600 including a plurality of reservoir computing units 400-1, 400-2, 401.

[0111] As Figure 6 shown, both the first reservoir computing unit 400-1 and the second reservoir computing unit 400-2 can be provided by a reservoir computing unit as described above with reference to Figure 4A the above. Figure 6 The third reservoir computing unit 401 shown in Figure 4B the above can be provided by a reservoir computing unit as described above with reference to

[0112] Figure 6 There is shown the first reservoir computing unit 400-1 and the second reservoir computing unit 400-2 arranged in parallel to provide inputs to the third reservoir computing unit 401 respectively. By connecting the first output terminal 440-1 of the first reservoir computing unit 400-1 to the first input terminal 411 of the third reservoir computing unit 401 and connecting the second output terminal 440-2 of the second reservoir computing unit 400-2 to the second input terminal 412 of the third reservoir computing unit 401, a hierarchical network is provided. In this way, the first unit 400-1 and the second unit 400-2 apply two parallel transformations to their respective inputs and then provide them as inputs to the third reservoir computing unit 401 to provide an output 440-3 based on two independent inputs and three transformations (i.e., one transformation for each unit).

[0113] It can be understood that a hierarchical network can be provided by arranging any number of reservoir computing units in the manner shown in Figure 5 and Figure 6 the above.

[0114] The stimulator has been described as applying electrical stimulation, but other types of stimulation can also be used. For example, the stimulator can be used to provide mechanical stimulation to a surface. For example, the stimulator can include electromechanical elements such as piezoelectric transducers. The stimulator can be used to provide chemical stimulation to a surface. Mechanical and / or chemical stimulation can be used as a supplement or alternative to the electrical stimulation described herein.

[0115] In an example of providing a reservoir computing system, each reservoir computing unit in the system can: have the same liquid in their respective reservoirs; or, at least one of the respective reservoirs has a liquid different from the other reservoirs; or, each of the respective reservoirs has a unique liquid.

[0116] Liquids with thin films are described herein, but embodiments of the present disclosure do not require thin films. Instead, embodiments can provide a simple liquid in the reservoir and can apply a stimulus to the surface of the simple liquid.

[0117] The wave measurement module can be coupled to the detector to The beam optical device is used to irradiate an area of the liquid thin film with a beam having a first polarization, and The light collector is coupled to the detector, and the light collector is used to receive the beam reflected by the liquid thin film, and the beam has a second polarization after reflection;

[0118] The wave measurement module described herein can be coupled to the light collector and / or the detector coupled to the light collector, so as to provide surface wave data based on the second polarization to characterize the Rayleigh waves in the liquid thin film.

[0119] The ranges recited herein should be understood to include the bounds of the recited range as well as any intermediate values between the two bounds.

[0120] Generally referring to the accompanying drawings, it can be understood that the functions of the systems and devices described herein are represented by schematic functional block diagrams. However, it can be understood that the functions need not be divided in this way and should not be construed as implying any particular hardware structure other than those described below and in the claims. The functions of one or more of the elements shown in the figures can be further subdivided and / or distributed throughout the devices of the present disclosure. In some embodiments, the functions of one or more of the elements shown in the figures can be integrated into one functional unit.

[0121] In some examples, the functionality of the controllers and processing devices (such as wave measurement modules) described herein can be provided by a combination of analog and / or digital processing and / or control functionality. It can include a general-purpose processor that can be used to execute any of the methods described herein. In some examples, the controller can include digital logic, such as a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a digital signal processor (DSP), or any other suitable hardware. In some examples, one or more storage elements can store data and / or program instructions for implementing the operations described herein. Embodiments of the present disclosure provide a computer program product, such as a tangible non-transitory storage medium, that contains operable program instructions for programming a processor to perform any one or more of the methods described and / or claimed herein, and / or to provide a data processing device described and / or claimed herein. Such a controller can include analog control circuitry that provides at least part of the control functionality. Embodiments provide analog control circuitry for performing any of the methods described herein.

[0122] The above embodiments should be understood as illustrative examples. Further embodiments are contemplated. It should be understood that any feature described in connection with any one embodiment can be used alone, or in combination with other features described, or in combination with one or more features of any other embodiment, or in any combination with any other embodiment. Additionally, equivalents and modifications not described above can also be used without departing from the scope of the invention. Equivalents should be duly considered when interpreting these claims.

Claims

1. A spectroscopic ellipsometry device for characterizing the interaction between a stimulus and a liquid film, the device comprising: A stimulator for providing a stimulus to a liquid film located on a certain volume of liquid to generate waves in the liquid film, there being an interface between the liquid film and the certain volume of liquid, A beam optical assembly for irradiating an area of the liquid film with a beam having a first polarization, and A light collector coupled to a detector, the light collector for receiving the beam reflected from the liquid film, the beam having a second polarization after being reflected by the liquid film; A wave measurement module coupled to the light collector and for providing surface wave data to characterize the Rayleigh waves in the liquid film based on the second polarization.

2. A spectroscopic ellipsometry device for providing a reservoir calculation unit used in a reservoir calculation system, the device comprising: A stimulator for providing a stimulus to a liquid to generate waves on the surface of the liquid, A beam optical assembly for irradiating an area of the liquid film with a beam having a first polarization, and A light collector coupled to a detector, the light collector for receiving the beam reflected from the surface, the beam having a second polarization after being reflected by the wave; A wave measurement module coupled to the light collector and for providing surface wave data based on the second polarization; An output for providing an output signal based on the surface wave data.

3. The apparatus according to claim 2, wherein, The surface of the liquid has a liquid film thereon, there being an interface between the liquid film and the liquid.

4. The device according to claim 2 or 3, wherein The stimulator is for providing the stimulus based on an output signal provided by another reservoir calculation unit.

5. The apparatus according to any one of claims 2 to 4, wherein The device is configured such that the effect of the Rayleigh waves can be determined from the surface wave data.

6. The device according to any one of the preceding claims, wherein, The surface wave data is based on: The s-polarization component of the second polarization, and The p-polarization component of the second polarization.

7. The device according to any one of the preceding claims, wherein, The surface wave data includes a first time series of samples, for example where the samples are collected from the liquid film.

8. The apparatus according to claim 7, wherein The wave measurement module is for providing a second time series based on the first time series, where the sampling rate of the second time series is lower than that of the first time series.

9. The device according to claim 8, wherein, The sampling rate of the second time series is at least 2 kHz, for example at least 10 kHz.

10. The device according to claim 9, wherein The second sampling rate is selected based on the size of the area.

11. The apparatus according to any one of the preceding claims, wherein, The beam includes a coherent beam, such as a laser.

12. The device according to any one of the preceding claims, wherein, The beam optical assembly focuses the beam.

13. The apparatus according to claim 12, wherein, The focus of the beam is positioned such that the beam is divergent when it reaches the light collector.

14. The apparatus according to any one of the preceding claims dependent on claim 1 or claim 3, wherein, The liquid film contains at least one of proteins and lipids.

15. The apparatus according to claim 14, wherein, The beam includes a wavelength selected according to the composition of the film.

16. The apparatus according to any one of the preceding claims dependent on claim 1 or claim 3, wherein, The beam is provided to the surface at an incident angle selected according to the composition of the film.

17. The apparatus according to any one of the preceding claims, wherein, The stimulator includes a test substance provider for contacting the surface of the liquid with a test substance to thereby provide the stimulus.

18. The apparatus according to any one of the preceding claims, wherein, The stimulator is for providing an electrical stimulus to the surface of the liquid, for example to the film.

19. The device according to any one of the preceding claims, wherein, The operation of the light collector is coupled to the operation of the stimulator such that surface wave data can be determined at a selected time after the stimulation, e.g., where the time is selected based on the location of the stimulation on the surface.

20. The apparatus according to any one of the preceding claims, wherein, For example, in the liquid film, the stimulator generates multiple wave modes, such as surface wave modes.

21. The apparatus according to claim 20, wherein, In addition to including Lucassen waves, the multiple wave modes further include at least one of capillary waves, gravity waves, and Rayleigh waves.

22. A method, comprising: Providing a stimulation to the surface of a liquid to generate waves on the surface, Irradiating a region of the liquid with a light beam having a first polarization, and Receiving the light beam after reflection by the waves, the light beam having a second polarization after being reflected by the waves; Determining surface wave data based on the received light beam based on the second polarization; and Providing an output signal based on the surface wave data.

23. The method according to claim 22, wherein, The surface of the liquid has a liquid film with an interface between the liquid film and the liquid.

24. The method according to claim 23, wherein, The surface wave data can characterize the Lucassen waves in the liquid film based on the second polarization.

25. The method according to any one of claims 22 to 24, wherein, The stimulation is based on an output signal provided by a reservoir calculation unit.

26. The method according to any one of claims 22 to 25, wherein The surface wave data is based on: the s-polarization component of the second polarization and the p-polarization component of the second polarization.

27. The method according to claims 22 to 26, wherein, The size of the region is defined by the size of the light beam on the surface and has a radius less than 1 mm.

28. The method according to claim 27, comprising focusing the light beam to provide the light beam size and such that the light beam is divergent when it reaches the light collector.

29. A reservoir calculation unit, comprising: An input end for receiving an input signal, A reservoir for containing a liquid, A spectroscopic ellipsometry device for measuring the response of the liquid contained in the reservoir to the stimulation based on the input signal, and An output end for providing an output signal based on the measured response.

30. The reservoir calculation unit according to claim 29, wherein, The spectroscopic ellipsometry device includes the spectroscopic ellipsometry device according to claim 1 or any one of claims 6 to 21 dependent on claim 1.

31. A reservoir calculation system, comprising at least one reservoir calculation unit according to claim 29 or 30 or at least one reservoir calculation unit provided by the device according to any one of claims 2 to 22 dependent on claim 2.

32. The reservoir calculation system according to claim 31, comprising a plurality of said calculation units coupled together, wherein, The stimulator of at least one of the calculation units is provided based on the output from at least one other unit of the multiple units.

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