Force measuring device and method

Abstract

According to an exemplary aspect of the invention, an apparatus is provided comprising: an elastic element having a spring constant; and a confocal chromatic aberration sensor configured to be optically connected to a surface of the elastic element for measuring displacement of the surface caused by a force.

Description

Technical Field

[0001] This disclosure relates to force measurement and related apparatus and methods. Background Technology

[0002] For example, force measurement is required in many research and industrial applications. For small forces, such as those in the micro-Newton range, techniques are typically based on microelectromechanical systems (MEMS) sensors or laser interferometry. For instance, an atomic force microscope (AFM) can be used to inspect surface profiles using a cantilever beam. However, due to the operating principle of AFM, the orientation and / or position of the AFM cantilever beam needs to be calibrated, and the lateral surface area used for measurement is quite small, for example, 1 mm by 1 mm. Furthermore, such devices may not be durable due to their small size. Therefore, a robust and durable device and method are needed to measure forces, such as microscopic forces in the micro-Newton or nano-Newton range. Summary of the Invention

[0003] This invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0004] According to a first aspect of the invention, an apparatus is provided comprising: an elastic element having a spring constant; and a confocal chromatic aberration sensor configured to be optically connected to a surface of the elastic element for measuring displacement of the surface caused by a force.

[0005] According to one aspect, the elastic element is a cantilever beam. In another aspect, the cantilever beam includes a non-fixed first end and a second end fixed to a mounting member. In yet another aspect, the first end and the second end are connected by a first strip and a second strip, wherein the first end, the second end, the first strip, and the second strip define an elongated hole between the first end and the second end.

[0006] According to a second aspect of the invention, a method is provided, comprising: providing an elastic element having a spring constant; guiding a confocal chromatic aberration beam onto a surface of the elastic element; and measuring the displacement of the surface caused by a force based on reflected light of at least one wavelength.

[0007] According to a third aspect of the invention, a method for obtaining a spring constant is provided, the method comprising: providing an elastic element; applying a predefined force to the elastic element to cause displacement of a surface of the elastic element; detecting the displacement of the surface of the elastic element using a confocal chromatic aberration sensor; and calculating a spring constant of the elastic element based on the predefined force and the displacement of the surface of the elastic element. Attached Figure Description

[0008] Figure 1A , 1B2A, 2B, 3A, 3B, 4A and 4B illustrate an apparatus according to at least some embodiments;

[0009] Figure 5A and 5B Examples of elastic elements according to at least some embodiments are shown;

[0010] Figure 6A and 6B Examples of elastic elements according to at least some embodiments are shown;

[0011] Figure 7 Example measurements that support at least some of the embodiments are shown;

[0012] Figure 8A , 8B 8C illustrates example measurements using a device according to at least some embodiments;

[0013] Figure 9A and 9B An installation component capable of supporting at least some of the embodiments is shown;

[0014] Figure 10A , 10B 10C illustrates a method according to at least some embodiments;

[0015] Figure 11 , 12 Figures 1 and 13 show graphs that can support at least some of the embodiments; and

[0016] Figure 14A and 14B An example of a resilient element capable of supporting at least some of the embodiments is shown. Detailed Implementation

[0017] Confocal chromatic aberration sensing provides distance information based on the dispersion of light, which has multiple wavelengths with different focal planes. Therefore, the reflection of one of these wavelengths depends on the focal plane of that wavelength. In other words, the distance to an object is determined based on spectral information of one or more reflected wavelengths. A confocal chromatic aberration sensor is configured to emit light of different wavelengths, each with a different focal plane and / or focus. Furthermore, the confocal chromatic aberration sensor is configured to measure the wavelength of light reflected from a surface, thereby providing the distance between the confocal chromatic aberration sensor and the surface based on the wavelength information.

[0018] The term "displacement" should be understood as the action of moving or repositioning an object from its position or place, and / or the amount by which an object moves from its position or place. Such displacement can be described as a distance, for example, in millimeters. The direction in which the displacement occurs can be included in the displacement. Therefore, displacement can be, for example, a real number or a vector. The term "deflection" should be understood as a change in the orientation or path of an object, such as the displacement of a cantilever beam or a portion thereof. In at least some embodiments, displacement is represented by "Δx" or "δ".

[0019] As used in the context of this disclosure, the term "hole" should be understood as a material defect defined by the surface of one or more material objects. For example, a material object, such as a cantilever beam or its structure, may have a hole such that the cantilever beam or its structure defines the hole. A hole may also be referred to as a "cut-off portion." A "cut-off portion" should be understood as a hole that is not necessarily limited by its manufacturing method. In other words, in at least some embodiments, the cut-off portion is obtained by means other than "cutting off" a portion of a material object, for example, using additive manufacturing. In at least some other embodiments, the cut-off portion is obtained, for example, by cutting (such as laser cutting).

[0020] The embodiments of this disclosure offer several advantages. Wavelength-based distance measurements provide results without requiring preliminary calibration of the positioning, which depends on, for example, light intensity or wavelength. For example, atomic force microscopy (AFM) utilizes laser-based detection, thus requiring a baseline of the AFM cantilever beam detection to infer the deflection of the AFM cantilever beam and the reflected laser beam. In contrast, since confocal chromatic aberration sensing is based on the instrument's optical design, which provides wavelengths with different focal planes, such calibration is not required. Therefore, at least some embodiments are superior to laser interferometry because the chromatic aberration confocal sensor provides absolute position and is also more robust in measuring tilted surfaces, which is advantageous for deflection measurements (e.g., the deflection of a cantilever beam and the displacement of its surface).

[0021] According to this disclosure, an apparatus is provided, comprising: an elastic element having a spring constant; and a confocal chromatic aberration sensor configured to be optically connected to a surface of the elastic element for measuring displacement of the surface caused by a force. Such a force may be, for example, gravity, electricity, magnetism, pressure, friction, static friction, adhesion, vibration, resistance, or a combination thereof.

[0022] According to this disclosure, an "elastic element" refers to an object or part thereof that, after a force is applied, is able to return to the shape and / or position that the object had before the force was applied. An elastic element can be, for example, a helical coil, a leaf spring, or a cantilever beam. Elasticity should be understood as the ability of an object or material to return to its shape after a force is applied. The elastic element can be defined at least in part by its spring constant. The "spring constant" k is a characteristic of the elastic element that defines the stiffness of the elastic element. In at least some embodiments, the spring constant of the elastic element is from 0.0001 to 1000 N / m, from 0.0054 N / m to 0.7 N / m, or from 0.01 to 1 N / m (Newtons per meter).

[0023] In at least some embodiments, the elastic element comprises at least one of the following: metal, plastic, or ceramic. In at least some embodiments, the elastic element comprises ceramic, such as glass, like borosilicate glass. In at least some embodiments, the elastic element comprises plastic, such as polylactic acid (PLA), nylon (polyamide), acrylonitrile butadiene styrene (ABS), or polycarbonate (PC). In at least some embodiments, the elastic element comprises metal, such as at least one of the following: titanium (Ti), copper (Cu), or aluminum (Al). In at least some embodiments, the elastic element comprises titanium (Ti). In at least some embodiments, the elastic element comprises at least one of the following: titanium, copper, 4130 steel, 1080 spring steel, copper, or glass.

[0024] The term "optical connection" should be understood as meaning that a confocal chromatic aberration sensor can operate such that at least a portion of the photons emitted by the confocal chromatic aberration sensor are reflected back to the confocal chromatic aberration sensor. In other words, the surface of the elastic element is configured to at least reflect at least a portion of the photons emitted thereon.

[0025] In at least some embodiments, at least a portion of the surface of the elastic element (through which the confocal chromatic aberration sensor is configured for optical connection) includes a reflective surface. The reflectivity of this reflective surface may be, for example, at least 10% or at least 5% of the received light. In at least some embodiments, the reflective surface is smooth and / or highly reflective, such that 40% of the received light is reflected. In at least some embodiments, at least a portion of the surface through which the elastic element and the confocal chromatic aberration sensor are optically connected is polished to provide a reflective surface at least on a portion of the surface of the elastic element.

[0026] Examples of the apparatus 100 according to at least some embodiments are shown in Figure 1A and Figure 1B As shown in [the image]. Figure 1AThe image shows an elastic element 110 having a spring constant k. The elastic element 110 includes a surface 110a, to which a confocal chromatic aberration sensor 120 is configured to be optically connected. During operation, such as during force measurement, the surface 110a of the elastic element may displace due to the applied force, such as... Figure 1B As shown. Therefore, the displacement Δx describes the positional difference of surface 110a at different stages (and / or time points), for example, at Figure 1A and Figure 1B The displacement can be derived from wavelengths 121 with different focal planes, which are reflected from surface 110a and received by confocal chromatic aberration sensor 120.

[0027] In at least some embodiments, the apparatus further includes means for calculating the force applied to the elastic element based at least on the spring constant and the measured displacement. In at least some embodiments, the apparatus includes a computing device configured to calculate the force applied to the elastic element based at least on the spring constant and the measured displacement.

[0028] Figure 2A and 2B An example of device 200 is shown, which includes an elastic element 210 having a spring constant k. Figure 2A and 2B The elastic element 210 is a helical coil. The elastic element 210 includes a surface 210a, to which the confocal chromatic aberration sensor 220 is configured to be optically connected. As can be understood from the figure, when a force is applied to the elastic element 210 (e.g., a force applied by the mass block 230), Figure 2B When the surface shifts from a certain distance (i.e., displacement Δx), the surface displaces by a certain distance. Figure 2A Position displacement to Figure 2B The position, displacement Δx, can be obtained based on the focal plane of the wavelength 221 used, through the change in distance between the confocal chromatic aberration sensor 220 and the surface 210a.

[0029] Using the measured displacement Δx and the spring constant k of the elastic element, the force F applied to the elastic element or a portion thereof can be calculated, for example, using F = kΔx. Therefore, the device can be configured to measure the force applied to an object based at least on the spring constant of the elastic element and the measured displacement of the elastic element surface relative to the confocal chromatic aberration sensor.

[0030] An example of an elastic element is a cantilever beam. As used in the context of this disclosure, the term "cantilever beam" should be understood as a protruding structure with one end supported (i.e., fixed) and the other end unsupported (i.e., non-fixed). In other words, a cantilever beam is an elongated structure extending from a fixed end to a non-fixed end. For example, a cantilever beam may extend horizontally. According to this disclosure, an apparatus is provided comprising: a cantilever beam having a spring constant; and a confocal chromatic aberration sensor configured to be optically connected to a surface of the cantilever beam to measure displacement of the surface caused by a force.

[0031] In at least some embodiments, the cantilever beam has a rectangular or substantially rectangular cross-section perpendicular to the cantilever beam's elongation direction.

[0032] Figure 3A and 3B A device 300 is shown, in which a cantilever beam 310 is an elastic element. The cantilever beam 310 has a non-fixed end 311 and a fixed end 312. The cantilever beam 310 is attached to a mounting member 350, thereby fixing or connecting the fixed end 312. A confocal chromatic aberration sensor 320 is configured to be optically connected to a surface 310a of the cantilever beam 310. The confocal chromatic aberration sensor is configured to emit wavelengths 321 having different focal planes. Figure 3A The document also presents an illustrative example of a graph 340a, which shows the wavelength 321 detected by the confocal chromatic aberration sensor 320. The position of the cantilever beam surface 310a relative to the confocal chromatic aberration sensor 320 is calculated, at least based on the reflected light.

[0033] exist Figure 3B The example displacement Δx is shown in the figure. Figure 3A similar, Figure 3B An illustrative example of graph 340b is presented. Based on the wavelength reflected from the cantilever beam surface and the wavelength detected by the confocal chromatic aberration sensor 320, the position and / or distance of the surface 310a of the cantilever beam 310 relative to the confocal chromatic aberration sensor 320 can be calculated. Therefore, based on the force applied to the cantilever beam 310, the displacement Δx can be calculated based on the measured wavelength spectrum, such as... Figure 3A and Figure 3B Examples of wavelength spectra in plots 340a and 340b are shown.

[0034] In at least some embodiments, the force F applied to the elastic element (e.g., a cantilever beam) is calculated based at least on the displacement Δx measured using a confocal chromatic aberration sensor and the spring constant k of the elastic element, for example, using Hooke's law and the equation F=kΔx.

[0035] At least some embodiments are suitable for measuring force. Such embodiments can use a confocal chromatic aberration displacement sensor to measure cantilever beam deflection. This confocal chromatic aberration sensor provides optimal resolution for deflection measurement, thus producing very good force resolution.

[0036] Confocal chromatic aberration technology is based on the dispersion of white light, which results in different backscattered spectra at different focal planes. This technology is primarily used in industry for rapid and accurate product quality assessment on production lines. For example, this could be for surface roughness or thickness measurement. In at least some embodiments, this technology is used to measure cantilever beam deflection with sub-micron accuracy in force sensing and mass measurement applications. The material and geometry of the cantilever beam can be adjusted to match its spring constant with the desired force resolution. In at least some embodiments, the material suitable for the force sensor cantilever beam includes a 0.05 mm thick titanium plate, which should produce force resolution down to the nanoNewton level.

[0037] Figure 4A and 4B A schematic example of the working principle of the force sensor 400a and the mass balance 400b is shown respectively.

[0038] In at least some embodiments, the force sensor is used for adhesion measurements using scanning droplet adhesion microscopy (SDAM). At least such embodiments offer the advantage that when the measured force approaches nanoNewtons, this means that sensors based on MEMS, for example, begin to encounter difficulties. SDAM is a technique for measuring forces, comprising a force sensor with a droplet probe and a multi-axis sample stage. The droplet can include, for example, water. A sample is attached to the sample stage and brought into contact with the droplet probe. The interaction between the sample and the probe is measured, thereby allowing the force to be calculated.

[0039] Figure 4A The components of a scanning droplet adhesion microscope (SDAM) force sensor 400a are schematically shown. The output of sensor 400a is a distance measurement given by the controller of a distance sensor (i.e., a confocal chromatic aberration sensor 420). This confocal chromatic aberration sensor 420 is connected to external hardware, such as a computing device, via optical fiber 422. Lines 421 from the measuring head of the confocal probe 420 represent the dispersed light and the focal planes of different wavelengths.

[0040] exist Figure 4A In this configuration, a cantilever beam 410 is attached to a mounting member 450, thus having a fixed end 412 and a non-fixed end 411. A confocal chromatic aberration sensor 420 is optically connected to the cantilever beam 410 via a surface 410a. According to... Figure 4A The force sensor 400a utilizes an SDAM probe attached to or included in the cantilever beam 410. In this SDAM probe, a disk 416 (e.g., an SU-8 disk) is attached to the cantilever beam 410.

[0041] exist Figure 4A The image also shows sample 480 and its sample surface 480a. A cantilever beam 410 has a disk, such as an SU-8 disk, attached thereto. Furthermore, a liquid droplet 418 is attached to said disk 416. The disk 416 and the droplet 418 thus form the probe of device 400a. Since device 400a is suitable for SDAM measurements, surface characteristics, such as surface adhesion, can be inferred through the interaction between the droplet 418 and the surface 480a of sample 480, via the displacement of at least a portion of the cantilever beam and its surface. Therefore, based on the deflection of the surface 410a of cantilever beam 410 and the measured wavelength distribution (i.e., wavelength spectrum), the force caused by the interaction between the probe and the surface 480a of sample 480 can be calculated.

[0042] Measuring force also allows for the measurement of weight, meaning that cantilever beam force sensors can be used for high-precision mass measurement.

[0043] Figure 4B An example of a mass balance setup 400b is shown. In other words, a device 400b suitable for measuring the force induced by a mass block 430 is shown. A confocal chromatic aberration sensor 420 is configured to be optically connected to surface 410a of the cantilever beam 410. Figure 4A Same, Figure 4B The cantilever beam 410 has a fixed end 412 and a non-fixed end 411. Therefore, based on the deflection of the cantilever beam 410 and the measured wavelength distribution (i.e., wavelength spectrum), the force applied by the mass block 430 can be calculated.

[0044] Different cantilever-based force sensors exist, a typical example being atomic force microscopy (AFM). In at least some embodiments, the force sensor design differs from these (such as AFM) in at least two ways: the force sensor uses a confocal chromatic aberration sensor for distance measurement, and the cantilever beam of such a force sensor is specifically designed to provide the required force resolution and is easily adjustable for different applications.

[0045] The term "adjustable" should be understood to mean, at least based on the material and geometry of the elastic element, that the elastic element may have a spring constant that depends on such geometric design and material decisions. In at least some embodiments, with respect to a cantilever beam, such "adjustable" characteristics depend at least to some extent on the size of the hole (in other words, the "cut-off portion") and the cantilever beam, as well as the material contained within the cantilever beam. The ratio of the hole size to the cantilever beam size may affect the spring constant, thereby affecting the spring constant. In at least some embodiments, the hole is a rectangular or substantially rectangular hole.

[0046] The advantage of confocal chromatic aberration sensors over laser interferometry is that they provide absolute position and are more robust when measuring tilted surfaces, which is important for deflection measurements.

[0047] Figure 5A and 5B An example of a force sensor cantilever beam 510 with a specific geometry is shown. It should be noted that cantilever beams conforming to this disclosure may have different geometries depending on the application and embodiment.

[0048] exist Figure 5A The image shows a two-dimensional view of the cantilever beam 510, while... Figure 5B A perspective view of the cantilever beam 510 is provided. The cantilever beam 510 is an elongated object. The cantilever beam 510 includes a first end 511 and a second end 512, as well as a first strip 513 and a second strip 514. The first end 511, the second end 512, the first strip 513, and the second strip 514 define an elongated hole 515 extending along the cantilever beam 510, the elongated hole being located between the first end and the second end. The hole may also be referred to as a cut-off portion. The first end 511 includes a surface 511a to which a confocal chromatic aberration sensor can be optically connected.

[0049] In at least some embodiments, the external dimensions of the cantilever beam are 1 mm to 1000 mm in the length direction (l), 0.5 mm to 500 mm in the width direction (b), and 0.01 mm to 50 mm in the thickness direction (t). In at least some embodiments, the cantilever beam includes a hole sized such that the hole is 1 mm to 1000 mm in the length direction (l). c The width ranges from 1 mm to 999 mm, and the width direction (b) c The range is from 0.3 mm to 499 mm.

[0050] In at least some embodiments, the external dimensions of the cantilever beam are 10 mm to 200 mm in the length direction (l), 1 mm to 10 mm in the width direction (b), and 0.5 mm to 5 mm in the thickness direction (t). In at least some embodiments, the cantilever beam includes a hole sized such that the hole is 1 mm to 200 mm in the length direction (l). c The thickness ranges from 5 mm to 80 mm in the width direction (b) c The width (b) is 2 mm to 6 mm, and the hole size is selected such that the corresponding size of the hole is smaller than the corresponding external size of the cantilever beam. In one embodiment, the width (b) is less than 75% of the length (l), for example, less than 50% of the length (l). In one embodiment, the width (b) is... c (b) is 25-95% of the width (b). In another embodiment, both numerical and percentage values ​​apply to the cantilever beam.

[0051] In at least some embodiments, the thickness (t) of the cantilever beam is 0.1 to 0.5 mm, for example 0.2 mm, the length (l) is 50 mm to 100 mm, for example 65 mm, and the width (b) is 1 mm to 5 mm, for example 2 mm. In at least some embodiments, such a cantilever beam includes a hole, the size of which is within the length (l) of the cantilever beam. c The width is 25 mm to 75 mm, for example 50 mm, and the width is (b c The size of the hole is 1.2 mm to 1.6 mm, for example 1.3 mm, and the size of the hole is selected such that the corresponding size of the hole is smaller than the corresponding external size of the cantilever beam.

[0052] "Strip" should be understood as a narrow strip of material. In at least some embodiments, the strip (e.g., a first strip and / or a second strip) has a length of 1 mm to 999 mm, a thickness of 0.01 mm to 50 mm, and a width of 0.1 mm to 499 mm. In at least some embodiments, the width of the strip (e.g., a first strip and / or a second strip) is 0.1 mm to 50 mm, or 0.5 mm to 25 mm. The strip size provides the advantage that the size at least partially affects the spring constant of the elastic element, thereby affecting the measurable displacement.

[0053] The hole 515 in the cantilever beam 510 and its dimensions may affect the spring constant k of the cantilever beam 510, thereby affecting the sensing characteristics of a device including such a cantilever beam 510. Therefore, the cantilever beam can be “tuned” to different force sensitivities via geometry and construction that affect the spring constant k.

[0054] Cantilever beams including holes (e.g.) Figure 5A and 5B The cantilever beam shown offers at least the following advantage: the cantilever beam structure can be constructed with a predetermined spring constant or a spring constant within a predetermined range. In other words, the spring constant is affected by the geometry of the cantilever beam (e.g., the hole size and the widths of the first strip 513 and the second strip 514). The material of the cantilever beam also affects the value of the spring constant or the range of the spring constant.

[0055] In at least some embodiments, the force sensor setup is part of a scanning droplet adhesion microscopy (SDAM) apparatus. This force sensor setup can be implemented onto the SDAM apparatus. The geometry of the force sensor cantilever beams can be fabricated using a laser cutter. These cantilever beams can be made from 0.2 mm thick copper sheet metal, thus producing a higher spring constant compared to 0.05 mm titanium cantilever beams. Nevertheless, initial tests on these cantilever beams showed good sensitivity results. Figure 7 A measurement is shown in which a droplet comes into contact with the surface of an aluminum sample and is then pulled off.

[0056] exist Figure 7 The diagram illustrates the measured force as a function of time. It shows adhesion measurements performed using a cantilever beam with a thickness of 0.2 mm and a spring constant of 2.21 N / m. The cantilever beam comprises copper and has a cut-off geometry, i.e., it has elongated holes. Droplets with a final volume of 5 μL were grown on the SU-8 disk of the cantilever beam, and the results were... Figure 7 The force is observed to increase linearly and remain constant until the droplet suddenly contacts the aluminum surface at approximately 80 seconds (“intrusion”). The stage is then stopped, and the droplet is pulled out (“pull-out”). Oscillations are observed at approximately 10 seconds as the droplet detaches. Therefore, the cantilever beam design according to at least some embodiments of this disclosure shows promising force resolution because the mass (or weight) of a 5-microliter droplet is detectable.

[0057] In at least some embodiments, the SDAM force sensor is a droplet probe comprising a cantilever beam to which an SU-8 disk is attached. The SU-8 disk can be used as a droplet holder. In other words, a droplet can be attached to the SU-8 disk, for example. Figure 4A An example component of a force sensor, including an SU-8 disk, is shown. The cantilever beam 410 is a key component of the sensor because its spring constant k and dynamic characteristics are important to the sensor's quality. Dynamic characteristics include, for example, damping characteristics. The confocal chromatic aberration sensor (e.g., Micro-Epsilon confocal DT IFS2405-1 with a 2451 controller) provides multiple wavelengths and outputs data by receiving the reflected wavelengths. In other words, the acquired and output data includes multiple wavelengths reflected from the cantilever beam surface. The resolution of the distance sensor, together with the characteristics of the cantilever beam, defines the resolution of the force sensor.

[0058] Confocal displacement sensors can be used for non-contact distance measurement in many applications. Compared to methods such as laser interferometry, this confocal chromatic aberration sensor offers several advantages, such as safety and robustness to environmental disturbances. The sensor's operation is partly based on the theory of light dispersion and confocality. The sensor can use an LED as a white light source. The white light is fed from the controller to the sensor head via optical fiber. In the sensor head of the confocal chromatic aberration sensor, a series of lenses focuses the light beam onto a small spot, for example, about 10 mm from the sensor head. Due to the dispersion of light, different wavelengths are focused on different focal planes. When light is scattered from a surface, the backscattered spectrum has an intensity distribution that depends on the wavelength of the focus. This is the idea behind the confocal theory of chromatic aberration. An analogy can be drawn with confocal microscopy, where the image is generated by an object on the focal plane (typically with a small depth of field). For example, at the upper limit of the 1 mm measurement range, the backscattered spectrum converges into the long-wavelength (red) spectrum. This spectrum can be analyzed in the controller of the confocal sensor. The signal can be transmitted from the confocal sensor to the controller via optical fiber. Preliminary tests show that the digital output significantly reduces noise compared to analog output paired with a 16-bit analog-to-digital converter. Ethernet outputs data at a sampling rate of 10 kHz, which can then be downsampled in the control software. The fact that the confocal sensor uses dispersion enables it to achieve a resolution of 28 nanometers. This is impossible to achieve with classical optics, as the wavelength of white light (400-700 nanometers) is the resolution limit in classical optics. Furthermore, the confocal sensor offers safety advantages based on its use of white light instead of a powerful laser.

[0059] In at least some embodiments, when the distance to a static object is measured and the standard deviation of the distance measurement is taken, the resolution of the confocal displacement sensor is approximately ±0.1 micrometers. This means that, according to Hooke's Law, P = kδ, where k is the spring constant of the cantilever beam, P is the force, and δ is the deflection of the cantilever beam, a spring constant k of approximately 0.01 N / m is required to achieve a force resolution of 1 nN.

[0060] In at least some embodiments, the confocal displacement sensor has a resolution of ±1 nanometer. Therefore, for a spring constant k of 0.01 N / m, a force resolution of 10 piconewtons can be obtained.

[0061] In at least some embodiments, the force resolution of the device is less than 1 micro Newton or less than 1 nano Newton. In at least some embodiments, such force resolution is obtained by an elastic element having a spring constant of 0.0001 N / m to 1000 N / m or 0.005 N / m to 1 N / m.

[0062] As previously mentioned, the cantilever beams used for force sensors according to at least some embodiments have relatively low spring constants while still being able to withstand noise from the environment (airflow and acoustic excitation), thus keeping noise levels within reasonable limits. The initial idea was to use microscope slides, but substituting the material parameters of borosilicate glass into the analytical solution for k showed that slides with rectangular cross-sections did not readily achieve the required spring constant. This is why simulations were performed on metal cantilever beams with cut-off sections.

[0063] After testing different cut-off geometry, a rectangular cut-off geometry (i.e., a rectangular cantilever beam with an extruded rectangular cut in the z-direction) was tested. At least some embodiments (where the elastic element is a cantilever beam) utilize a rectangular cut-off portion. Figure 5A and 5B This geometry was visualized.

[0064] A dynamic mode refers to a measurement mode in which displacement caused by a force is measured at at least two different time points. In at least some embodiments, the device is configured to measure displacement in a dynamic mode. Furthermore, the dynamic mode may include measuring the oscillation of an elastic element caused by a force. This force may also be time-varying, such as oscillation. Because the oscillation of the elastic element caused by the force may be continuous, the elastic element (e.g., a cantilever beam) should have appropriate damping parameters.

[0065] When using structures with low spring constants, small or minute forces can cause the structure to displace or deflect. Therefore, although sensitive to small forces, structural oscillations can hinder force measurements because force-induced oscillations can persist for extended periods. Thus, measures to dampen oscillations in the elastic element may be necessary. In at least some embodiments, damping can be reduced by applying devices to reduce oscillations, with damping parameters ranging from 0.01 1 / s to 10,000 1 / s, 0.02 1 / s to 1 1 / s, or 0.019 1 / s to 0.87 1 / s (per second). In at least some embodiments where the elastic element is a cantilever beam, damping can be achieved by offsetting the lengths of the first end (non-fixed end) and the second end (fixed end) of the cantilever beam. In other words, the length of the first end can be longer than the second end. In at least some embodiments, damping can be enhanced by a layered or “sandwich” structure including a damping material such as rubber. Examples of rubber include synthetic rubber. Synthetic rubbers include, for example, styrene-butadiene rubber, nitrile rubber, and butyl rubber.

[0066] In at least some embodiments, the cut-off portion of the cantilever beam is centered on the y-axis and has a width of b. c Millimeters. The length of the excised portion in the x-direction is l. c= (l - 10) mm, and has an offset of 2 mm from the fixed end of the cantilever beam. In at least some embodiments, the reason for the unequal offset is that the tip of the cantilever beam has more mass to improve damping. Similarly, in at least some embodiments, the non-fixed end (i.e., the first end) has more material to provide more options for attaching probes (such as SU-8 disks) at different positions and / or orientations.

[0067] The spring constant of the cut-off portion of a cantilever beam depends, at least in part, on the dimensions of the cut-off portion and the cantilever beam. This means the thickness t, length l, and size b of the cut-off portion. c and l c These are likely important parameters because they affect the spring constant k. The tested thickness values ​​were chosen based on the thickness of commercially available metal sheets, and 60 mm was used as the starting point for the cantilever beam length l. The initial cut-off value was b. c =1.5 mm, l c = (l - 10) millimeters, and b c Later, optimizations were made to fine-tune the cantilever beam characteristics. The width b was kept constant at 2 mm. The simulated cantilever beam materials were titanium, 6063 alloy, 4130 steel, 1080 steel, and copper. For each material, the initial dimensions were (l × b × t) = (60 mm × 2 mm × 0.1 mm) and (l... c × b c = (50 mm × 1.5 mm).

[0068] In addition to using the parameters t, l, and b c In addition to geometry optimization, cantilever beams can also be adjusted by adding a rubber layer that provides elastic damping and improves the damping parameter ξ. A sandwich geometry of a Ti-rubber-Ti layer structure is one option for achieving this. Figure 6A and 6B This sandwich structure is illustrated. In at least some embodiments, the layered structure (e.g., a three-layer structure) for cantilever beams includes a metal-rubber-metal layer structure.

[0069] Figure 6A and 6B A cantilever beam 610 with a layered structure is shown. The middle layer (second layer) comprises a rubber material, while the bottom layer (first layer) and the top layer (third layer) comprise metal. The first layer is on top of the second layer, and the second layer is on top of the third layer. Figure 6B It shows Figure 6A Enlarged view 690 of the area shown by the dashed line. The cantilever beam 610 includes a cut-off portion 615, defined by a first end 611, a second end 612, a first strip 613, and a second strip 614 of the cantilever beam 610. Regarding... Figure 6BThe enlarged view 690 shows the first strip 613 and the second strip 614. The third layers 613c and 614c are on the second layers 613b and 614b, and the second layers 613b and 614b are on the first layers 613a and 614a. The first end 611 includes a surface 611a to which a confocal chromatic aberration sensor can be optically connected.

[0070] To understand the characteristics of different cantilever beam materials and designs, simulations were performed using COMSOL for various options. Two types of solid mechanics simulations were performed: a static simulation with point loads and a time-dependent simulation with ramp point load inputs. The static simulation was computationally less demanding and was therefore used to optimize the cantilever beam dimensions. The time-dependent simulation, also known as the dynamic mode simulation, provided information about the cantilever beam's spring constant k and damping constant ξ, parameters that describe the sensor resolution and noise level.

[0071] For the COMSOL simulation, the droplet 418 and SU-8 disk 416 are modeled as simple point loads, and the clamping portion (i.e., the fixed end) of the cantilever beam is considered to remain fixed. Figure 4A The geometry in the model shown is simplified. The point load assumption is reasonable because the droplet 418 and disk 416 are rotationally symmetric about the z-axis, and the load and cantilever beam width b are small, with negligible bending in the y-direction. The assumption of a fixed clamping portion (i.e., fixed to the mounting) means that the cantilever beam in the simulation has a fixed end at x = 0, and the cantilever beam length l is the length of the free-hanging portion (also known as the non-fixed end). The point load location is assumed to be on the centerline (y = 0) and 2 mm from the tip of the cantilever beam. The materials used from the COMSOL material library are: Titanium with Ti Grade 1 [solid, annealed], Aluminum with Aluminium 6063-T83, 4130 steel with 4130 [solid, quenched and tempered], 1080 spring steel with 1080 [solid, polished], Copper with copper [solid, polished], and Borosilicate A for the coverslip glass. Static simulations were performed by applying gravity and a point load P and running the model. Because these simulations are used to test and optimize multiple parameter combinations (l, t, b) c (and materials), therefore, COMSOL LiveLink for MATLAB is used to automate the workflow. This allows the model geometry to be automatically defined, and the point loads to be easily changed. The output is the z-component of the deflection field w(l⁻²) = δ from the point load location. For each set of parameters, the point load P is varied, and a linear model is fitted to the F(δ) data to find the spring constant k.

[0072] For the time-dependent simulation, a simulation duration of 30 seconds and a time step of 0.01 seconds were chosen. The initial conditions for the deflection field were set to zero because the gravitational component of the deflection is different for each cantilever beam. Therefore, gravity is applied gradually. Otherwise, the simulation would not converge on the first time step since gravity acts as a step-function load. Therefore, the gravitational acceleration in the simulation varies with time, as shown below:

[0073]

[0074] The ramp input for point loads is selected as follows: for cantilever beams with t < 0.2 mm, the ramp increases from 0 μN to 1 μN over 3 seconds, then decreases back to 0 μN; for cantilever beams with t ≥ 0.2 mm, the maximum value is set to 10 μN. The ramp is selected to start at t = 15 seconds because at this time a gravity (t) has reached a steady-state value. For both time-dependent and static cases, the mesh used was the COMSOL physics control option with the "ultra-fine" cell size option. This option has a maximum cell size of 2.1 mm, a minimum size of 0.09 mm, a maximum cell growth rate of 1.35, a curvature factor of 0.3, and a narrow-area resolution of 0.85. For the final cantilever beam geometry, the mesh was manually refined to study convergence.

[0075] Figure 8A An example device 800a is shown in three different stages. Device 800a includes a cantilever beam 810 as an elastic element, the cantilever beam 810 including a probe 818a. A confocal chromatic aberration sensor 820 is optically connected to the cantilever beam 810 via a confocal beam 821 having multiple focal planes based on wavelength. When the sample stage 880 is moved so that the sample 881 contacts the probe 818a, the surface characteristics of the sample 881 are measurable based on the displacement of the cantilever beam 810, which can be measured by the confocal chromatic aberration sensor 820. The surface characteristics of the sample 881 may be, for example, the surface roughness of the sample 881, the adhesion of the probe 818a to the sample surface 881, and / or the surface profile of the sample 881.

[0076] Figure 8BExample apparatus 800b is shown in three different stages. Apparatus 800b includes a cantilever beam 810 as an elastic element, the cantilever beam 810 including a probe 818b. Such a probe 818b may include, for example, tissue or cells, thereby providing a means for bioadhesion measurements. A confocal colorimetric sensor 820 is optically connected to the cantilever beam 810 via a confocal light 821 having multiple focal planes based on wavelength. When the sample stage 880 is arranged relative to the cantilever beam such that the sample 881 contacts the probe 818b, the surface characteristics of the sample 881 are measurable based on the displacement of the surface of the cantilever beam 810, which can be measured by the confocal colorimetric sensor 820. The surface characteristics of the sample 881 may be, for example, the surface roughness of the sample 881, the adhesion of the probe 818a to the surface of the sample 881, and / or the surface profile of the sample 881.

[0077] Figure 8C An example device 800c is shown, comprising a cantilever beam 810 as an elastic element. It is understood that the displacement of the cantilever beam surface can be measured using a confocal chromatic aberration sensor 820. This displacement can be caused by force, and... Figure 8C In this context, the force is gravity caused by mass block 830.

[0078] It is understood that the design of elastic elements provides versatility in force measurement, such as mass measurement, or adhesion (e.g., bioadhesion) measurement. Depending on the embodiment, different probes can be used, such as... Figure 4A , 8A And the probe shown in 8B. In addition, at least some embodiments can be used to perform lateral scanning of the sample surface, thereby providing at least one of the following information: adhesion, stiffness, static friction, friction, or sample surface profile.

[0079] According to this disclosure, a method for manufacturing a cantilever beam is provided, the method comprising: obtaining a material, such as a sheet material; and forming an elongated cantilever beam from the material including a hole defined by a first end, a second end, a first strip, and a second strip. Thus, a cantilever beam having a cut-off portion (i.e., a hole, such as an elongated hole) is provided. Such a cantilever beam has at least the advantage that the hole size (i.e., the cut-off portion size) and the external dimensions of the cantilever beam can be selected such that the cantilever beam obtains a suitable spring constant or a range of spring constants.

[0080] In at least some embodiments, the cantilever beam according to this disclosure is manufactured using additive and / or subtractive manufacturing. Additive manufacturing (e.g., 3D printing) can be used to manufacture the cantilever beam, for example using photopolymerization (e.g., UV resin manufacturing) or extrusion methods such as fused deposition modeling (FDM), also known as fused filament fabrication (FFF).

[0081] In at least some embodiments, the cantilever beam is manufactured by laser cutting. An actual manufacturing example is as follows. The cantilever beam can be cut from a metal sheet using a laser cutter, such as a Laser Micromachining System (LMS). The LMS is a custom tool from Aalto Nanofab that allows cutting at a resolution of a few micrometers. The cantilever beam design can be provided to the LMS in .dxf format, and in the LMS software, the cut is defined by filling the cantilever beam profile with contour lines 0.1 mm wide and 0.02 mm apart. To reduce warping, the cutting is performed in stages, allowing the cutter to perform five repetitions, after which the cut can be visually inspected and any additional repetitions assessed. The initial prototype cantilever beam was made from a 0.2 mm thick copper sheet, requiring four sets of five repetitions (a total of 20 repetitions) to cut through when using full laser power (5 volts). For titanium sheets with thicknesses of 0.05 mm and 0.127 mm, the warping problem became more pronounced, so the laser power was reduced to 10% of its maximum value (0.5 volts). This reduced warping, but the titanium plate was still so warped that the laser could no longer be properly focused for cutting. Therefore, copper cantilever beams were the only cantilever beams used in the experiments. The dimensions of these cantilever beams are shown in Table 1. Reducing titanium plate warping can be achieved, for example, by using an initial plate size larger than the 50 × 50 mm plate used here, and placing a block of aluminum with the cut portion above the plate as a weight and cooling element.

[0082] Table 1: Properties of the cantilever beams used in the experiments. The “Cu rect” cantilever beams have no cut-off sections so that they can be used to compare analytical, simulated, and experimental spring constants. The length l here is the actual “free” length measured after installation.

[0083]

[0084] In at least some embodiments, the cantilever beam can be fixed to the mounting component. Figure 9A and 9B An example embodiment of the mounting structure 950 is shown. The mounting 950 has a designated slot 953 for the cantilever beam 910, and the mounting 950 securely clamps the cantilever beam 910 between the top 952 and bottom 951 of the slot 953. Two 6 mm alignment pins 954a, 954b and two M6 bolts ensure uniform clamping force and prevent the mounting from twisting even if the cantilever beam 910 is only located in a small portion of the mounting 950. Figure 9BAn example is shown where a cantilever beam 910 is attached to a mount 950 from the second end 912. The cantilever beam 910 is not fixed from the first end 911. The cantilever beam 910 can be mounted to the mount 950 by placing the cantilever beam 910 on 3D-printed retainers 958a, 958b, which align the cantilever beam 910 with a sample stage, then using the sample stage to position the cantilever beam 910 inside the mount and tightening the mount 950. This ensures that the cantilever beam 910 is perpendicular to the mount 950 and an optional rear-view camera (not shown), and parallel to a side-view camera (not shown).

[0085] In at least some embodiments, the mounting member comprises metal. In at least some embodiments, the bottom portion 951 of the mounting member 950 comprises brass, and the top portion 952 comprises aluminum. Alignment pins 954a, 954b may comprise steel and may be secured to the bottom portion 951 with an H7 fit. The mounting member 950 may be designed to be mounted to a 25 mm aluminum profile using two bolts 955a, 955b and a notch 956 for alignment.

[0086] Figure 10A , 10B Figures 10 and 10C illustrate at least some steps of a method for attaching the SU-8 disk 1016 to the cantilever beam 1010. Figure 10A In the process, glue 1017 is dispensed from dispenser 1018. Figure 10B The image shows a UV adhesive droplet 1017 and an aligned SU-8 disk 1016. Figure 10C In the process, after placing the disk 1016 on the sample stage and curing the UV adhesive with UV light (UV light pen), the SU-8 disk 1016 is located on the cantilever beam 1010.

[0087] In at least some embodiments, the SU-8 disk can be attached to the cantilever beam as follows: UV adhesive is used to attach the SU-8 disk to the cantilever beam, which makes it easier to ensure a smooth joint than double-sided tape. A small amount of adhesive is used to prevent it from spreading to the sides of the SU-8 disk. Otherwise, a small amount of adhesive might dissolve into the droplets, potentially contaminating them.

[0088] Dispensers can be used to deliver small drops of glue at desired locations on a cantilever beam, as exemplified by... Figure 10A As shown. A side view of the cantilever beam 1010 and the dispenser 1018 is shown. Due to the high viscosity of the UV adhesive, a large dispenser nozzle (such as the BioFluidiX PipeJet 500-L) is used to dispense the adhesive. After dispensing the adhesive ( Figure 10B ), bringing the SU-8 disk into contact with the cantilever beam, as shown in the example. Figure 10B and 10CAs shown. Use a UV pen to cure the UV adhesive for about 2 minutes to establish a firm contact between the disk and the cantilever beam. Figure 10C The SU-8 disk 1016, which has been erected on the cantilever beam 1010, is shown.

[0089] Static and dynamic COMSOL simulations can be used to find the optimal cantilever beam design based on geometry and materials. Parameters such as cantilever beam material, spring constant, and damping parameters are listed in Table 2. From the table, it can be observed that, except for the glass slide, static and dynamic simulations yield the same spring constant k. The spring constant results show that, for the same cut-off geometry, at least aluminum, titanium, and copper appear to be suitable candidate materials for achieving a spring constant of 0.01 N / m. The thicknesses of the last two titanium cantilever beams in Table 2 are readily available from standard laboratory equipment suppliers, and we actually see that a 0.05 mm thick titanium plate provides a spring constant even less than the required one.

[0090] In terms of damping characteristics, the 0.05 mm titanium cantilever beam is inferior because the thinner sheet thickness reduces damping. Copper differs from a 0.1 mm thick sheet with k < 0.1 N / m in that it has the highest damping parameter ξ, at 0.22 1 / s. However, it should be noted that damping is primarily important while waiting for the oscillation to stabilize. Such oscillations may arise from droplet distribution and pull-out events, and here, 10–20 seconds is still an acceptable timeframe. Most COMSOL simulations show step response oscillations decaying within that timeframe. Furthermore, the simulation was conducted with an empty SU-8 disk, but with droplets, it provides more mass to the cantilever beam, damping the oscillations and altering the system's characteristic frequency.

[0091] Since the results in Table 2 indicate that a 0.05 mm titanium plate can provide a sufficiently low spring constant, it was used for geometry optimization. The parameter that was changed was the width b of the cut-off portion. c Using 76 different b c A static simulation is run with values ​​(ranging from 0.75 mm to 1.5 mm), and the point load P is varied to find the value as b. c The spring constant of the function. Using 5 different values ​​of P, a total of 380 simulations are required. k(b) c The result is as follows Figure 11 As shown, it can be observed that when the width b of the cut portion... c When the thickness is 1.3 mm, a 0.05 mm titanium cantilever beam should be able to achieve the required spring constant. Figure 11 It shows different cut-off portion widths b cThe spring constant of the cut-off portion of the titanium cantilever beam is shown. Since the results are simulated, numerical noise is present, but we can observe a general trend where the spring constant decreases as the width of the cut-off portion increases. This is logical, as the cross-sectional area of ​​the cut-off portion, which constitutes most of the cantilever beam's length, becomes smaller.

[0092] Table 2: Simulated spring constant k and damping parameters of different cantilever beams obtained through dynamic and static simulations. For k, the error order of the static simulation is 10⁻⁶ N / m or less. Here, all cantilever beam dimensions are l = 60 mm, b = 2 mm, l c = 50 mm, b c = 1.5 mm. Thickness t is specified in the cantilever beam type column.

[0093]

[0094] One aspect that COMSOL simulations do not consider is the displacement limit w between elastic deformation and plastic deformation. max If the cantilever beam displacement remains small, this is not a problem, but from a sensor characteristics perspective, this would be valuable information because the limit defines the force measurement range for a given cantilever beam. Limit w max Experimental tests can be performed using SDAM settings because the sample stage can provide precise displacement, and the onset of plastic deformation can be observed using a camera or distance sensor.

[0095] The force sensor noise and force resolution were tested through an evaporation experiment, and the obtained force-time curve is shown below. Figure 12 As shown. In Figure 12 The figure shows the force P measured from the evaporation experiment. m (t) and the calculated force P c (t). The calculated and measured results based on image analysis matched quite well, but drift could be observed in the data. The inset in the figure shows the last 200 seconds of the experiment, showing that the calculated force still exceeded 0.3 micronewtons when the measured force could be negative due to noise. The measured force was obtained using a cantilever beam "Cu 0.2", and the calculated force was obtained through image analysis and volume calculation. Figure 12 The results show that the measured force exhibits considerable noise and drift because the calculated force value is not centered on the noise level of the measured value throughout the experiment. This is attributed to drift in the distance sensor or difficulty in finding the correct baseline position in the volume calculation algorithm. However, the fact that the difference is initially positive but becomes negative at the end suggests that sensor drift is the most likely cause. Therefore, for very long scan measurements, the force sensor should be recalibrated intermittently to eliminate the effects of drift.

[0096] To determine the resolution of the force sensor using the cantilever beam “Cu 0.2”, the absolute error |P| between the calculated force and the measured force was calculated. m -P c |, and in Figure 13 As shown in [the image]. Figure 13 The figure shows the absolute error between the measured force and the calculated force during the evaporation experiment. Based on the accuracy of the calibration volume calculation, it can be assumed that the calculated value has a significantly smaller error than the measured value. The average error is approximately 50 times the error contribution implied by the distance sensor, which means that environmental noise is significant.

[0097] from Figure 13 We observed an average error of 0.2 micronewtons, but there were also peak values ​​approaching 2 micronewtons. These peaks are likely due to environmental noise, as the evaporation experiment is quite long (approximately 25 minutes), so factors such as someone entering the lab and causing airflow would be reflected in the sensor output. Figure 13 The sensor noise under optimal conditions is also plotted using dashed lines. In this case, the error comes only from the distance sensor's resolution. This would correspond to a resolution of 42 nanonewtons, but there could be other noise sources. Therefore, from... Figure 13 Estimates suggest that the actual resolution is approximately 0.5 micronewtons, since the forces of interest must be detectable from noise.

[0098] On the other hand, it should be noted that these measurements were performed without a vibration isolation table and without enclosing the setup. Therefore, a resolution of approximately 0.5 micronewtons is suitable for the setup in its current state, and would be significantly improved when an enclosure and active vibration isolation table are added. Such an approach may be necessary for further cantilever beam development, as it makes sense to manufacture more sensitive cantilever beams if the setup can be isolated to a level where environmental excitation is less than the distance sensor error.

[0099] As presented above in at least some embodiments, the spring constant can be obtained or approximated by modeling the structure of the elastic element (e.g., a cantilever beam) using geometric and material information. Therefore, the spring constant can be obtained by structural modeling of the elastic element. Furthermore, the spring constant of the elastic element (e.g., a cantilever beam) can also be obtained, for example, by applying a predetermined force to the elastic element, measuring the displacement of the surface of the elastic element, and calculating the spring constant of the elastic element based on the predetermined force and the surface displacement, for example, based on Hooke's law.

[0100] An example of calibrating and obtaining the spring constant of an elastic element is as follows. To obtain the spring constant, a liquid of known density is applied to the elastic element in a device (e.g., devices 100, 200, 300, 400a, 400b, 800a, 800b, or 800c) in the form of droplets of known volume, and the corresponding displacement of the surface of the elastic element is measured using a confocal chromatic aberration sensor. The mass of the droplet is then calculated based on its volume and the liquid density, thereby calculating the weight applied by the droplet. The spring constant k is obtained based on, for example, Hooke's law and the equation k = F / Δx, based on the displacement Δx of the elastic element surface and the force F applied to the elastic element.

[0101] Figure 14A An example elastic element is shown, which is a cantilever beam 1410a. The cantilever beam 1410a includes a first end 1411 and a second end 1412 connected by a first strip 1413 and a second strip 1414, thereby defining an elongated hole 1415 between the first end 1413 and the second end 1414. The mesh structure may include at least one strand connecting the first strip and the second strip. Figure 14A It is understood that the multiple strands 1416a of the mesh structure 1416 connect the first strip 1413 and the second strip 1414 to each other. The mesh structure can restrict the lateral movement of the cantilever beam, thereby providing rigidity to the structure. In at least some embodiments, the strands and / or the mesh structure comprise the same material as the cantilever beam.

[0102] In one embodiment, the cantilever beam is provided with sufficient lightness, flexibility, and rigidity through a structure in which the cantilever beam includes a first strip and a second strip, such that the first strip and the second strip connect a first end and a second end. To provide rigidity, the cantilever beam also includes at least one crossbar that connects the first strip to the second strip in a region located between the first end and the second end. The number of crossbars can be, for example, one, two, three, four, five, or more than five. In these embodiments, holes or openings are formed between the ends and the crossbars. If the embodiment has at least two crossbars, at least one hole or opening is also formed between adjacent crossbars.

[0103] In one embodiment, the cantilever beam is provided with sufficient lightness, flexibility, and rigidity through a structure in which the cantilever beam includes at least two holes between a first end and a second end. In another embodiment, the cantilever beam has an elongated body connecting the first and second ends, and the holes are disposed within this elongated body. The number of holes can be selected according to the desired characteristics of the cantilever beam. This number can be, for example, two, three, four, at least five, or at least ten.

[0104] Figure 14BAn example elastic element is shown, which is a cantilever beam 1410b. The cantilever beam 1410b includes a first end 1411 and a second end 1412 connected by a first strip 1413 and a second strip 1414, thereby defining an elongated recess 1415b between the first end 1413 and the second end 1414. Figure 14B The recess 1415b, shown in the area defined by the dashed line, is therefore a cavity or depression in the cantilever beam 1410b. In other words, the material in the recess is less than the material in the surrounding cantilever beam structure. In at least some embodiments, the thickness (t) of the cantilever beam outside the recess is greater than the thickness (t) inside the recess. r That is, t > t r The recess 1415b can provide rigidity in the lateral direction. In at least some embodiments, the recess 1415b includes a mesh structure, such as similar to... Figure 14A The structure presented in the text.

[0105] In at least some embodiments, the environmental conditions and / or the medium in which the elastic element is located can be, for example, air and / or typical ambient conditions such as standard temperature and pressure (STP). However, in at least some other embodiments, other media can be used. For example, the medium can be a liquid. In other words, at least a portion of the device, such as the elastic element or a portion thereof (e.g., a probe), can be immersed in a liquid, such as underwater. In at least some embodiments, measurements can be performed under microgravity, such as in space and / or on a satellite.

[0106] It should be understood that the embodiments of the invention disclosed herein are not limited to the specific structures, process steps, or materials disclosed herein, but extend to equivalents that would be recognized by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0107] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrases "in one embodiment" or "in one embodiment" appearing throughout this specification do not necessarily refer to the same embodiment.

[0108] As used herein, multiple items, structural elements, constituent elements, and / or materials may be presented in a common list for convenience. However, these lists should be interpreted as if each member in the list were individually identified as an independent and unique member. Therefore, any single member in such a list should not be interpreted as a de facto equivalent of any other member in the same list simply based on their presentation in a common group unless otherwise indicated. Furthermore, various embodiments and examples of the invention, as well as alternatives to its various components, may be referenced herein. It should be understood that these embodiments, examples, and alternatives should not be construed as de facto equivalents of each other, but should be regarded as independent and autonomous representations of the invention.

[0109] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details, such as examples of length, width, shape, etc., are provided in the following description to provide a thorough understanding of embodiments of the invention. However, those skilled in the art will recognize that the invention can be practiced without one or more specific details, or using other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring various aspects of the invention.

[0110] While the foregoing examples illustrate the principles of the invention in one or more specific applications, it will be apparent to those skilled in the art that numerous modifications in form, usage, and implementation details can be made without exercising inventive capacity and without departing from the principles and concepts of the invention. Therefore, the invention is not intended to be limited except by the claims set forth below.

[0111] The verbs “comprising” and “including” are used in this document as open-ended restrictions, neither excluding nor requiring the presence of any unrecorded features. Unless otherwise expressly stated, the features recited in the dependent claims may be freely combined with each other. Furthermore, it should be understood that the use of “a” or “an” throughout this document, i.e., the singular form, does not exclude the plural form.

[0112] Industrial applicability

[0113] At least some embodiments of this disclosure have industrial applicability in the field of measuring and sensing force.

[0114] List of abbreviations AFM (Atomic Force Microscope) FFF melt filament manufacturing FDM fused deposition modeling LED Light Emitting Diode LMS Laser Micromachining System MEMS (Micro-Electro-Mechanical Systems) PLA (polylactic acid) ABS Acrylonitrile Butadiene Styrene PC (Polycarbonate) SDAM scanning droplet adhesion microscopy

[0115] List of reference numerals

[0116]

[0117]

Claims

1. A device for measuring force, comprising: - An elastic element that has a spring constant; as well as - A confocal chromatic aberration sensor is configured to be optically connected to the surface of the elastic element in order to measure the displacement of the surface caused by force.

2. The apparatus according to claim 1, wherein the apparatus further comprises: - A means for calculating the force applied to the elastic element based at least on the spring constant and the measured displacement.

3. The apparatus according to claim 1 or claim 2, wherein the spring constant of the elastic element is 0.0001 to 1000 N / m, or 0.0054 to 0.7 N / m.

4. The apparatus according to any one of the preceding claims, wherein the damping parameter of the elastic element is 0.01 l / s to 10000 l / s, 0.2 l / s to 1 l / s, or 0.019 l / s to 0.87 l / s.

5. The apparatus according to any one of the preceding claims, wherein the apparatus is suitable for scanning droplet adhesion microscopy (SDAM) measurements.

6. The apparatus according to any one of the preceding claims, wherein the apparatus is configured to measure displacement in a dynamic mode, wherein the displacement caused by force is measured at at least two different time points.

7. The apparatus of claim 6, wherein the dynamic mode includes measuring oscillations caused by force.

8. The device according to any one of the preceding claims, wherein the elastic element comprises at least one of the following: titanium, copper, 4130 steel, 1080 spring steel, copper, or glass.

9. The apparatus according to any one of the preceding claims, wherein the elastic element is a cantilever beam.

10. The apparatus of claim 9, wherein the cantilever beam includes a first end and a second end, wherein the first end is non-fixed and the second end is fixed to a mounting member.

11. The apparatus of claim 10, wherein the surface is located at the first end of the cantilever beam.

12. The apparatus of claim 10 or claim 11, wherein the cantilever beam includes a first strip and a second strip, the first strip and the second strip connecting the first end and the second end such that the first strip and the second strip define an elongated hole in the cantilever beam located between the first end and the second end.

13. The apparatus of claim 10 or claim 11, wherein the cantilever beam includes a first strip and a second strip, the first strip and the second strip connecting the first end and the second end such that the first strip and the second strip define an elongated recess in the cantilever beam located between the first end and the second end.

14. The apparatus of claim 12 or claim 13, wherein the elongated recess or the elongated hole comprises a mesh structure containing at least one strand connecting the first strip and the second strip via the recess or the elongated hole.

15. The apparatus of claim 10 or claim 11, wherein the cantilever beam comprises a first strip and a second strip, the first strip and the second strip connecting the first end and the second end, the cantilever beam comprising at least one crossbar connecting the first strip to the second strip in a region located between the first end and the second end.

16. The apparatus of claim 10 or claim 11, wherein the cantilever beam includes at least two holes between the first end and the second end.

17. The apparatus according to any one of claims 9 to 14, wherein the cantilever beam comprises a layered structure, wherein the layered structure comprises a first layer, a second layer on the first layer, and a third layer on the second layer.

18. The apparatus of claim 17, wherein the first layer comprises metal, the second layer comprises rubber, and the third layer comprises metal.

19. The apparatus of claim 17 or 18, wherein the first layer comprises titanium, the second layer comprises rubber, and the third layer comprises titanium.

20. The apparatus according to any one of claims 9 to 19, wherein the external dimensions of the cantilever beam are 1 mm to 1000 mm in length, 0.5 mm to 500 mm in width, and 0.01 mm to 50 mm in thickness, or 50 mm to 100 mm in length, 1 mm to 5 mm in width, and 0.1 mm to 0.5 mm in thickness.

21. The apparatus according to any one of the preceding claims, wherein the surface of the elastic element comprises a reflective surface, the reflective surface being smooth and / or reflective such that at least 10% of the light is reflected.

22. A method comprising: - Provides elastic elements with spring constants; -Guide the confocal chromatic aberration beam onto the surface of the elastic element; as well as - The displacement of the surface caused by force is measured based on reflected light of at least one wavelength.

23. The method of claim 22, wherein the method further comprises: - Calculate the value of the force that causes the displacement based on the displacement and the spring constant.

24. The method of claim 22 or claim 23, wherein the confocal chromatic aberration beam comprises at least two different wavelengths having different focal planes.

25. The method according to any one of claims 22 to 24, wherein the measurement further comprises: - Measure the displacement of the surface caused by the force at at least two time points; as well as - Calculate the value of the force causing the displacement based on the displacement at the at least two different time points and the spring constant.

26. The method of claim 25, wherein the measurement includes measuring oscillations caused by force.

27. The method according to any one of claims 22 to 26, wherein the elastic element is a cantilever beam including a first end, a second end, a first strip and a second strip, wherein the first end is non-fixed, the second end is fixed to a mounting member, and wherein the first strip and the second strip connect the first end and the second end such that the first strip and the second strip define an elongated hole in the cantilever beam located between the first end and the second end.

28. The method according to any one of claims 22 to 27, wherein the method further comprises obtaining the spring constant of the elastic element by: - The displacement of the surface of the elastic element caused by a predefined force is measured using the confocal chromatic aberration sensor; and - Based on the predefined force and the measured displacement, the spring constant of the elastic element is obtained.

29. The method of claim 28, wherein the predefined force is obtained by: - A droplet of known density and known volume is applied to the elastic element, thereby causing displacement of the surface of the elastic element; and - Calculate the predefined force based at least on the volume and density of the droplet.

30. A method for obtaining a spring constant, the method comprising: -Provide flexible elements; - A predefined force is applied to the elastic element, thereby causing displacement of the surface of the elastic element; - The displacement of the surface of the elastic element is detected using a confocal chromatic aberration sensor; as well as - Calculate the spring constant of the elastic element based on the predefined force and the displacement of the surface of the elastic element.

31. The method of claim 30, wherein the predefined force is obtained by: - At least one droplet of liquid, having a known volume and a known density, is applied to the elastic element; and - Calculate the predefined force based on the known volume and known density.

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