Patent Publication Number: US-2015089693-A1

Title: Multi-resonant detection system for atomic force microscopy

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This patent application makes reference to and claims priority to U.S. Provisional Patent Application Ser. No. 61/881,573, filed on Sep. 24, 2013, which is hereby incorporated herein by reference in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY FUNDED RESEARCH AND DEVELOPMENT 
     This invention was made with government support under Contract No. DE-AC05-00OR22725 between UT-Battelle, LLC. and the U.S. Department of Energy. The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present disclosure relates to atomic force microscopy and more specifically to a multi-resonant detection system for atomic force microscopy. 
     2. Related Art 
     An atomic force microscope may include a cantilever with a sharp tip (probe) which may be used to scan the surface of a specimen or sample material. The cantilever may be made of silicon and/or silicon nitride, for example, with a tip radius of curvature which may be on the order of nanometers. The cantilever and tip may be part of an atomic force microscopy (AFM) chip fabricated from a single silicon wafer. In instances when the tip and the specimen surface are brought into close proximity, interaction forces between the tip and the sample may cause deflection of the cantilever. Static and dynamic forces at work on the tip may be detected based on the deflection. Sensitivity of the detection process may be greatly enhanced in instances when the cantilever is made to operate on resonance, and therefore act as a mechanical amplifier of tip motion. Characteristics of the cantilever, such as resonance, may be determined by the size and shape of the cantilever and may not be adjustable while taking measurements. These characteristics may affect efforts to measure frequency dependent parameters of a specimen since the characteristics of the cantilever determine which frequencies can be amplified. 
     In AFM measurements, the cantilever and tip may measure aspects of the surface of a specimen. The cantilever and tip may be conductively coated and a bias may be applied to the tip. In a standard AFM apparatus, the cantilever may be flexible and may extend to the tip which may mechanically or physically touch the specimen surface. Some measurements may be conducted to determine whether, in instances when a bias is applied to the tip, how that bias changes the specimen surface in a local area. For example, the applied bias may change the height of the surface or it might change the mechanical, electrical or other material properties of the surface the sample. Also, in the case of a ferroelectric specimen, the polarization of an electric field in the specimen may change direction. For example, when an external electric field is applied to an ionically conductive material by the AFM tip, the ion concentration and local charge distribution inside or on the surface of the material may change. In this regard, battery materials may be studied using a biased AFM tip. In some AFM systems, measurements may be taken in a liquid either with or without applied bias, where the cantilever and tip may oscillate within the liquid. In order to do very sensitive measurements of a material in standard AFM, the cantilever may be run on resonance, for example, at one or more modes of the cantilever and tip. When the cantilever is driven with a force at a certain frequency or mode, it will shake or vibrate with much greater amplitude than at other frequencies. The presence of liquid, stray electric or magnetic fields and changes in mass of the tip (due to tip breaking or picking up of material) may have an effect on the dynamic characteristics of the AFM cantilever and these effects may be accounted for during analysis of the AFM results. 
     BRIEF SUMMARY OF THE INVENTION 
     Disclosed are several examples of a multi-resonant detection system and method for making atomic force microscopy measurements. An atomic force microscopy (AFM) chip may comprise an AFM tip, a cantilever which is mechanically coupled to the AFM tip and one or more resonator members. The one or more resonator members may be positioned separately in the AFM chip relative to the cantilever and the AFM tip. Frequency of motion of the AFM tip and the cantilever may be detected by one or more of the resonator members. Also, motion of the AFM tip and the cantilever may be actuated by the one or more resonator members. 
     Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The system may be better understood with reference to the following drawings and description. Non-limiting and non-exhaustive descriptions are described with reference to the following drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  illustrates an oblique view of a multi-resonant detection system chip for atomic force microscopy. 
         FIG. 2  illustrates a front oblique view of detection and amplification apparatus in a multi-resonant detection system chip for atomic force microscopy. 
         FIG. 3  illustrates an isolated front oblique view of detection and amplification apparatus in a multi-resonant detection system chip for atomic force microscopy. 
         FIG. 4  illustrates an isolated front oblique view of detection and amplification apparatus during resonator excitation at a particular frequency in a multi-resonant detection system chip for atomic force microscopy. 
         FIG. 5  illustrates a detection and amplification apparatus comprising a continuous membrane resonator. 
         FIG. 6  illustrates an exploded oblique view of detection and amplification apparatus in a multi-resonant detection system chip for atomic force microscopy including top and bottom cover plates. 
         FIG. 7  is a frequency plot demonstrating how six resonator bars in a multi-frequency detection system may respond over a wide range of frequencies. 
         FIG. 8  illustrates a multi-resonant detection system chip within an atomic force microscopy test set-up. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A multi-resonant detection system for atomic force microscopy (AFM) may comprise a chip fabricated by photolithographic, micro- or nanofabrication, and machining manufacturing techniques. The chip may be made of one or more materials or multiple layers of materials, which are suitable for making micro-mechanical devices, for example, silicon, silicon oxide, silicon nitride, polydimethylsiloxane (PDMS), gold, platinum, titanium, and carbon. In some systems, the chip may be fabricated by many of the same techniques that are used in standard AFM chip manufacturing. The multi-resonant detection AFM chip may include an AFM tip which extends from a rigid or non-resonant cantilever where the cantilever may act as an acoustic, force, or displacement transmission line to one or more remote resonators or an array of resonators, for example. In this regard, the non-resonant cantilever may be interactively coupled to the one or more remote resonators. In some systems, a resonator array may resemble a xylophone and may include resonator bars of varying length, and therefore varying resonances. In some systems each of the resonator bars may be connected or clamped at both ends to more rigid members of the multi-resonant detection AFM chip. In other systems each resonator bar may be clamped at one end while the other end is free to vibrate. In some systems, motion of the resonator bars may be detected using laser deflection and a photodetector or an interferometer, for example. However, by positioning the resonator bars away from the tip and cantilever, various other displacement detection schemes may be utilized, for example, capacitance, piezo-strain, piezo-resistive and other displacement detection methods. The resonators or resonator bars are not limited to having a bar shape or any other specific shape and may have any suitable shape or shapes, for example, wires or tubes. A resonator bar may be referred to as a resonator or a resonator member, for example. Additionally, the resonator bars may be designed to work as actuators where they may be used to drive tip and cantilever motion with cleaner drive signals than currently available methods. Although the design may include resonator bars of varying length, a similar effect may be achieved by varying other aspects of the resonators, for example, the resonator bars may have the same length, but their effective masses may vary. For example, in some systems, the bars may be thicker in a small region at the center of the bars. The system is not limited with respect to any specific shape of the resonators and any suitable method of varying the resonance among the resonators may be utilized. 
     The multi-resonant AFM detection system may enable amplification of forces or displacements which are detected by the AFM tip over a broad range of frequencies. Unwanted external effects on cantilever dynamics, such as stray electric fields and liquid environments may be significantly reduced. Moreover, mechanical tip oscillations may be cleanly driven without the use of a piezo actuator and alternative means to detect tip deflection other than optical beam deflection are provided. 
     The multi-resonant AFM detection system may rely on the resonator bars rather than the AFM cantilever to provide mechanical amplification of the tip motion. In this regard, the mechanical amplification process may be moved further away from the AFM tip to a more protected region on the AFM chip. In some systems an array of mechanical resonators may be utilized, where the array may be designed to resonate over a broad range of discrete frequencies. Alternatively, a continuous resonator membrane may be used to provide a more continuous range of resonant frequencies. 
     As a result, many deleterious effects which may be imposed on an AFM amplification process by forces in the local environment of the tip and cantilever, may be avoided. For example, the local effects due to a liquid environment, stray electric and magnetic fields and changes in mass of the tip or cantilever (for example, due to the tip breaking or picking up material) that may impact dynamic characteristics of an AFM cantilever may be reduced or eliminated. Moreover, the multi-resonant design disclosed herein may enable significant amplification in any suitable region of the frequency spectrum and may provide better ways for detection in addition to laser deflection. 
     Now turning to the figures,  FIG. 1  illustrates an oblique view of a multi-resonant detection system (MRD) chip  100  for atomic force microscopy (AFM) including a detection and amplification portion  120  of the chip  100 . Also shown in  FIG. 1  is a specimen material  130  which may be referred to as a sample. 
     The MRD chip  100  may be fabricated from a silicon wafer. Photolithography and machining may be utilized to shape the chip. The MRD chip  100  may be a continuous, solid and/or single piece of silicon wafer that may include the detection and amplification portion  120 . The detection and amplification portion  120  may comprise apparatus that senses or detects forces or physical changes in the specimen material  120 . Also, the detection and amplification portion  120  of the MRD chip  100  may actuate tip motion to interact with the specimen  120 . Operation of the MRD chip may be controlled by an atomic force microscope, for example, by controlling signals applied to the detection and amplification portion  120  for driving mechanical tip oscillations and/or by reading amplified vibration signals from the detection and amplification portion  120  of the MRD chip  100  to detect tip deflection (see  FIG. 8 ). 
     The test system  100  may include additional components, such as additional circuitry, firmware and/or processing modules. For example, a controller module  7  and/or other modules in the test system  100  may comprise suitable logic, circuitry, interfaces and/or code that may be operable to determine and/or control bias waveforms and/or measure and compile results of measurements. Portions of test system  100  may be implemented by one or more integrated circuits (ICs) or chips. 
     In operation, the specimen material  130  may be positioned under the detection and amplification portion  120  so that properties of the surface of the specimen material  130  may be detected by the detection and amplification portion  120  and the results may be transmitted to a computing device in the atomic force microscope (see  FIG. 8 ). The multi-resonant detection system (MRD) chip  100  may be referred to as an atomic force microscopy (AFM) chip. 
       FIG. 2  illustrates an enlarged front oblique view of detection and amplification apparatus in a multi-resonant detection system chip for atomic force microscopy. Referring to  FIG. 2 , there is shown the multi-resonant detection system (MRD) chip  100  for atomic force microscopy (AFM) including the detection and amplification portion  120  and the specimen material  130  which may be referred to as a sample. Also shown are an AFM tip  210 , a cantilever  220  and one or more resonator bars  230 . The detection and amplification portion  120  may comprise the AFM tip  210 , the cantilever  220  and the resonator bars  230 , all of which are described with respect to  FIG. 3 . The AFM tip  210  may be positioned over the surface of the specimen material  130  and may detect changes in the specimen material. The AFM tip  210  may be referred to as the tip. 
       FIG. 3  illustrates an isolated front oblique view of the detection and amplification apparatus in a multi-resonant detection system (MRD) chip for atomic force microscopy. Referring to  FIG. 3 , shown are the detection and amplification portion  120 , the AFM tip  210 , the cantilever  220 , and one or more resonator bars  230  of the MRD chip  100 . Also shown are the rigid wall  340  and two flexible wall extensions  330 . 
     The detection and amplification portion  120  of the MRD chip  100  may include the AFM tip  210 , the cantilever  220 , one or more resonator bars  230 , the rigid wall  340  and the flexible wall extensions  330 , all of which may be included in the continuous, solid and/or single piece of silicon comprising the MRD chip  100 . Although a plurality of resonator bars are shown in the  FIGS. 1-4 , some systems may comprise only one resonator or a continuous membrane resonator (described with respect to  FIG. 5 ). The one or more resonator bars  230  may be referred to as a resonator, a resonator member, an array of resonators or resonator beams, for example. 
     The AFM tip  210  may extend from the cantilever  220 . The cantilever  220  may be referred to as a non-resonating cantilever. In this regard, although a non-resonating cantilever  220  may resonate at one or more frequencies, a non-resonating cantilever  220  may not have significant resonance at the one or more frequencies employed in the multi-resonant detection methods described herein. For example, the cantilever  220  may not resonate at a frequency matching the resonant frequencies of the one or more resonator bars  230  or of the continuous resonator membrane  530  (described with respect to  FIG. 5 ). A benefit of using a non-resonating cantilever  220  is that motion due to resonance of the cantilever  220 , the tip  210  and/or the rigid wall  340 , may not interfere with the multi-resonant detection system  100  operation or analysis. However, the system is not limited in this regard and in some systems, the cantilever  220  may have resonance characteristics that affect the MRD system operation or analysis. 
     The cantilever  220  may be mechanically coupled to the rigid wall  340 . The rigid wall  340  may be referred to as a rigid member or element of the MRD chip  100 . In some systems, the tip  210 , the cantilever  220  and the rigid wall  340  may comprise a rigid and/or non-resonant armature, such that they move together, for example, when driven by a force or when the AFM tip  210  is set in motion by the sample  130 . A bias may be applied to the tip  210  and/or the cantilever  220 , which may cause the tip  210 , the cantilever  220  and the rigid wall  340  to shake or vibrate together. In this regard, the spatial orientation of the tip  210 , the cantilever  220  and the rigid wall  340  may remain fixed relative to each other during the vibrations or rotations, for example. The rigid wall  340 , the cantilever  220  and the tip  210  together may be referred to as an armature or frame, for example. The non-resonating characteristic of the cantilever  220  may be different than other types of AFM cantilevers which are generally flexible and may bend and/or vibrate at resonant frequencies resulting in mechanical amplification of tip motion in the cantilever. However, rather than amplifying the motion of the tip  210 , the non-resonating cantilever  220  and rigid wall  340  may move together with the motion of the tip and may serve as an acoustical transmission line between the tip  210  and the one or more resonator bars  230  such that the tip  210  motion is transferred unamplified by the cantilever  220  and rigid wall  340  to the one or more resonator bars  230 . In this regard, the one or more resonator bars  230  may be interactively coupled with one or more of the non-resonating cantilever  220  and the tip  210 , for example, via the rigid wall  340 . 
     In some systems, since the cantilever  220  need not be an excellent resonator, the cantilever  220  may be pliant enough to reduce tip to surface forces while enabling high frequency measurements to be performed in the resonator cavity by the resonator array  230 . Furthermore, in some systems, the cantilever may be made to be very thin laterally and tall, similar to a fin to help reduce effects of added mass motion in liquids. 
     The flexible wall extensions  330  may be attached to the rigid wall  340  of the cantilever  220  and to a rigid wall of the MRD chip  100 . The flexible wall extensions  330  may enable the rigid wall  340 , the cantilever  220  and the tip  210  to move up and down or rotate, for example, when driven by a force from the resonator bars  230  or when the AFM tip  210  is set motion by the sample  130 , for example. In some systems the flexible wall extensions  330  may be operable to twist, stretch, rotate or swing, for example, to accommodate motion in the rigid wall  340 , the cantilever  220  and the tip  210  armature or to induce motion originating in the resonators  230  and imparted to the rigid wall  340 , the cantilever  220  and the tip  210  armature. In this manner, the triangular cantilever  220  may be rigidly connected to the rigid wall  340  and weakly connected through a flexible membrane of the flexible wall extensions  330  to the rest of the MRD chip  100 . 
     The one or more resonator bars  230  may be flexible elements in the MRD chip  100  and each may be operable to oscillate, shake or vibrate at one or more particular resonant frequencies or modes, depending on, for example, its size, shape and/or mass. The one or more resonator bars  230  may be rigidly attached or “clamped” to the rigid wall  340  and to a rigid or non-resonating wall or area of the MRD chip  100 . In other systems, one end of each resonator bar may be rigidly attached or “clamped” to the rigid wall  340  while the opposite end may be detached and free to vibrate. The size, shape and/or mass of each resonator bar  230  may vary such that each of the one or more resonator bars  230  may be tuned to a different resonant frequency. In this manner, forces over a range of frequencies may be detected and amplified by the array of resonant bars  230  (described further with respect to  FIG. 7 ). For example, longer bars may amplify lower frequency signals and relatively shorter bars may amplify higher frequency signals. Although the resonator bars  230  may be referred to as bars, the resonators or resonator bars are not limited to having a bar shape or any other specific shape and may have any suitable shape or volume. A resonator bar may be referred to as a resonator or resonator member, for example. An open space around the resonator bars  230  within the MRD chip  100  may be referred to as a resonator chamber or cavity. The resonator chamber may comprise a gas or may be encased to keep a liquid away from the resonators. Alternatively, the resonator chamber may hold a liquid environment for the resonators  230 . 
     In operation, the flexible walls  330  at either end of the rigid wall  340  may allow the rigid wall  330 , the cantilever  220  and the tip  210  to rotate or rock, for example, such that the tip  210  may be set into motion relative to the sample material  130 . The tip  210  may oscillate, shake or vibrate, at least, up and down relative to the sample material  130  surface to tap or touch the surface. The rigid wall  340 , the cantilever  220  and the tip  210  may rotate or rock together as one unit or armature, without internal resonance or amplification of the tip motion. 
     In some instances, the tip  210  may be set into motion by movement of the sample  130  or an external source such as shaking of the MRD chip  100 , and the motion of the tip  210  may be transmitted via the cantilever  220  and the rigid wall  340  to one or more of the resonator bars  230  for detection. Thus, a force on the tip  210  that is transmitted through the triangle of the cantilever  220  to the rigid wall  330  may cause the entire tip  210 , cantilever  220  and rigid bar  340  to rotate or move as a single unit. This displacement may cause one or more of the resonator bars  230  to vibrate at the frequency of the tip  210  and to amplify the tip motion. For example, in instances when the rigid wall  340 , the cantilever  220  and the tip  210  move or vibrate at a particular frequency, one or more of the flexible resonator bars  230 , which may have a resonant frequency or frequency mode corresponding to that particular frequency, may oscillate or vibrate at the resonant or modal frequency and may mechanically amplify the motion of the rigid wall  230 , the cantilever  220  and the tip  210 . 
     In other systems, one or more of the resonator bars may be driven to move or oscillate by an external source using electric, magnetic, thermal and/or photo-thermal effects. The motion of the one or more resonator bars  230  may cause the rigid wall  340 , the cantilever  220  and the tip  210  to move or vibrate at a frequency corresponding to the resonant frequency or resonant frequencies of the one or more resonator bars  230 . In this manner the one or more resonator bars  230  may actuate motion in the cantilever  220  and the tip  210 . 
     In some systems the specimen material  130  may be set in motion and make contact with the tip  210  during a detection process. For example, the specimen material  130  may be mounted to a piezo-electric crystal. An alternating current (AC) voltage may be applied to the piezo-electric crystal which may cause the crystal to oscillate and vibrate the specimen material  130 . The tip  210 , the cantilever  220  and the rigid bar  340  may be set in motion as a response to the vibrations of the sample material  130  touching or tapping the tip  210 , and may transmit the responsive motion and/or frequency to one or more of the resonating bars  230  according to the resonant and/or modal frequencies of the resonator bars  230 . The responsive motion of the tip  210  may be influenced by the hardness of the surface of the specimen sample  130  or by forces between the specimen material  130  and the tip  210 . In instances when a particular resonating bar  230  has a resonant frequency corresponding to the frequency of the responsive motion of the tip  210 , the particular resonating bar  230  may oscillate at its resonant frequency. 
       FIG. 4  illustrates an isolated front oblique view of detection and amplification apparatus during resonator excitation at a particular frequency in a multi-resonant detection system chip for atomic force microscopy.  FIG. 4  comprises elements that are shown in  FIG. 3 , including the detection and amplification portion  120 , the AFM tip  210 , the cantilever  220 , one or more resonator bars  230 , the rigid wall  340  and two flexible wall extensions  330  of the MRD chip  100 . However,  FIG. 4  illustrates displacement of one of the resonator bars  230 . The displacement be initiated as a response to motion of the tip  210 , the cantilever  220  and the rigid wall  340 , or may be initiated by stimulus applied to the resonator bars  230  and may be transferred to the rigid wall  340 , the cantilever  220  and tip  120 . 
       FIG. 4  comprises a model with fixed boundary conditions applied to the side and back edges of the model and a sinusoidal displacement applied to the end of the triangular cantilever  220 . This model approximates AFM modes such as piezo-response force microscopy (PFM), electrochemical strain microscopy (ESM), or atomic force acoustic microscopy (AFAM) in which small displacements of the sample surface drive tip  210  motion.  FIG. 4  illustrates an array of beam resonators  230  with one of the beams significantly deformed by the driving force applied to the end of the triangular cantilever  220 . Though the displacement of the tip  210  may be small, the beam  230  motion may be quite significant in instances when the frequency of tip  210  motion matches the resonant frequency of one of the beams  230 . 
     Motion and/or frequency of motion of the one or more resonant bars  230  may be detected in a variety of ways. For example, in some systems laser light may be shone on each of the resonator bars  230  such that motion of the resonator bars may cause changes in angle of reflections of the laser light. The changing reflection angle may be detected by a photosensor and motion and/or frequency of the tip  210  may be determined based on the laser reflections off of one or more particular resonant bars  230 . In some systems, interferometry may be utilized to detect the resonator motion. In other systems, capacitance, piezo strain or piezo resistive methods, for example, may be utilized to detect motion of the flexible resonator bars  230  or to drive their motion, as described below with respect to  FIG. 6 . 
       FIG. 5  illustrates a detection and amplification apparatus for a multi-resonant detection system chip comprising a continuous resonator membrane. Referring to  FIG. 5 , there is shown a portion of the MRD chip  100  including the detection and amplification portion  120 , the AFM tip  210 , and the cantilever  220 . Also shown is a continuous resonator membrane  530 . 
     In some systems, the MRD chip  100  may have a continuous flexible resonator membrane  530  in place of the flexible resonator bars  230 . In some systems, the continuous resonator membrane  530  may have a long triangular shape where the wide part of the triangle is resonant at lower frequencies and the narrow part is resonant at higher frequencies. However, the system is not limited with respect to the shape of the continuous resonator membrane  530 . Since the membrane is continuous there may be more ways in which it can vibrate relative to the discrete resonator bars  230 . The continuous resonator membrane  530  may yield a more continuous range of frequencies for detecting the motion of the tip  210  and cantilever  220  or for driving the tip and cantilever motion, as compared with fixed resonant frequency modes characteristic of discrete resonator bars  230 . The continuous resonator membrane  530  may be referred to as a resonator member. 
       FIG. 6  illustrates an exploded oblique view of a detection and amplification apparatus in a multi-resonant detection system chip for atomic force microscopy including top and bottom cover plates. Referring to  FIG. 6 , the detection and amplification portion  120  of the MRD chip  100  including the AFM tip  210 , the cantilever  220 , the one or more resonator bars  230 , the rigid wall  340  and the two flexible wall extensions  330  of the MRD chip  100  are shown. Also shown are a top cover plate  610 , a bottom cover plate  620  and one or more electrodes  630 . The electrodes  630  may be referred to as conductive strips, plates or a capacitor plate. 
     In some systems, the top cover plate  610  and/or bottom cover plate  620  may encase the resonators  230  in a cavity or chamber which may be partially open or may be hermetically sealed, for example. 
     In some systems, the bottom cover plate  620  may have electrodes  630  placed below the resonators  230  which may enable either detection or actuation of the resonators bars  230 . The bottom cover plate  620  may be an encasing layer of the MRD chip  100 . In some systems, the bottom cover plate  620  may be made of insulator material and may include one or more conductive strips or plates, for example, the electrodes  630 . The one or more electrodes  630  may form one or more capacitors with corresponding resonator bars  230 . In some systems, changes in capacitance between the electrodes  630  and corresponding resonator bars  230  may be used to either detect motion of the tip  210  or to drive motion of the tip  210 . 
     In an exemplary system, one or more capacitors may be formed by one or more of the resonator bars  230  and the one or more electrodes  630  which may be positioned beneath the one or more of the resonator bars  230 . For example, the one or more electrodes  630  may comprise a gold film  630  that may be placed beneath the encasing layer or bottom cover plate  620  on the bottom side of the MRD chip  100 . A direct current (DC) and or alternating current (AC) voltage bias may be established between the electrode  630  and the one or more resonator bars  230 . As a resonator bar  230  flexes up and down due to tip  210  and cantilever  220  motion at a certain frequency, the distance between the resonator bar  230  and a corresponding electrode  630  may vary and in turn the capacitance between the resonator bar  230  and the electrode  630  may vary. The varying capacitance may be measured to detect the motion and/or frequency of the motion of the tip  210 . As a resonator bar  230  flexes up and down with respect to a plate  630  below it, the capacitance may vary and generate an AC signal at a frequency which corresponds to frequency of tip  120  and cantilever  220  motion in a response relative to the specimen  130 . 
     Alternatively, the capacitor formed by the one or more electrodes  630  and one or more of the flexible resonator bars  230  above the electrodes  630  may be used to drive or generate motion in the cantilever  220  and tip  210 , for example, using an AC bias signal applied to the capacitor. In this regard, an AC voltage may be applied between one or more of the resonator bars  230  and a corresponding one or more electrodes  630  beneath them. The applied AC voltage may create a changing force between those conductive plates. The AC bias voltage may oscillate at a resonant frequency of at least one of the resonator bars  230 , the resulting force may cause at least one resonator bar  230  to vibrate or oscillate, which in turn may cause the cantilever  220  and tip  210  to move or shake relative to the specimen material  130  at the same or a corresponding frequency of the AC bias voltage. Furthermore, an AC signal may include any signal that changes in time and may or may not have multiple frequency components. For example, band excitation may be utilized that may include multi-frequency, non-sinusoidal excitation. 
     Alternatively, some systems may utilize piezo-electric or piezo-resistive methods for detection of tip  210  motion and/or for driving tip  210  motion. For example, the surface of one or more of the flexible resonator bars  230  may be coated with a piezoelectric or piezo-resistive material that may generate voltage or change resistivity when the film is deformed, for example, when the resonator bars flex up and down. In instances when one or more of the resonators  230  flexes up and down due to tip  210  and cantilever  220  motion, the flexure may cause pressure in the piezoelectric material and may generate AC voltage and/or current at a frequency corresponding to the frequency of the tip  210  and cantilever  220  motion. In some systems the piezoelectric coating may be placed on top of each of the flexible resonator bars  230  where pressure induces a bias across the material. In instances when an alternating current is applied to the piezoelectric coated resonator bars  230 , the changing signal may cause the resonator bars to flex up and down at the frequency of the AC signal and the motion may be transferred to the cantilever  220  and tip  210 . 
     In some systems, the top cover plate  610  and the bottom cover plate  620  may form hermetically sealed encasing layers that enclose the resonators  230  in a resonator cavity or chamber thereby enabling measurements in a liquid medium. In some systems, at least the top cover plate  610  may be made of a transparent material so that optical detection of a response in the resonator bars  230  may be made, for example, by detecting changing angles of laser light reflections at a photo detector. For example, the top cover plate  610  may be made of silicon nitride; however, the system is not limited in this regard. 
     In some systems the top cover plate  610  and/or the bottom cover plate  620  may form encasing layers which are made of a conductive material. The conductive encasing layers may be used to shield the resonators  230  from stray electric fields. 
     In some systems, one or more of the top cover plate  610 , the bottom cover plate  620  and the electrodes  630  may be machined from the same silicon or semiconductor wafer as the rest of the MRD chip  100 ; however, the system is not limited in this regard. For example, in some systems one or more of the top cover plate  610 , the bottom cover plate  620  and the electrodes  630  may be added to the MRD chip  100 . 
       FIG. 7  is a frequency plot demonstrating how six resonator bars in a multi-frequency detection system may respond over a wide range of frequencies. The resonator bars  230  described with respect to  FIGS. 1-5  may each respond in multiple flexural modes. Referring to  FIG. 6 , an exemplary response is shown for the first three modes of each of six resonators  230 . The solid black lines represent resonance peaks of a first mode of oscillation in each of the six resonators  230 . The dashed lines represent the resonance peaks of the second mode of oscillation in each of the six resonators and the dot-dash lines indicate the resonance peaks of the third mode of each of the six resonators. The amplitudes have been normalized to one. 
       FIG. 8  illustrates a multi-resonant detection system chip within an atomic force microscopy test set-up. Referring to  FIG. 8 , there is shown an AFM system  800  comprising the multi-resonant detection system (MRD) chip  100  for atomic force microscopy (AFM) and the specimen material  130 , described with respect to  FIGS. 1-7 . Also included are a computing system  850 , an AFM controller  840 , an AFM optical system  820  and a scanning stage  810 . 
     In some systems, the MRD chip  100  may comprise one or more traces, leads and or wires that that may be communicatively coupled to the AFM controller  840  and/or to the computing system  850 . 
     The computing system  850  may comprise one or more processors  854 , one or more memory devices  852  and/or one or more user interfaces  856 , for example. The computing system  350  may comprise suitable logic, circuitry, interfaces or code that may be operable to store and/or execute instructions for controlling the AFM system  800  and/or collecting, analyzing and/or displaying AFM system  800  data. The computing system  850  may be utilized to configure and/or control one or more of the elements of the AFM system  800 . The computing system  850  may be communicatively coupled to the AFM controller  840 . In some systems, the computing system  850  and the controller  840  may be integrated in one device or in other systems, may be distributed in a plurality of devices. The AFM controller  840  may also be communicatively coupled to one or more of the MRD chip  100 , the AFM optical system  820  and the scanning stage  810 . The AFM controller  840  may comprise suitable logic, circuitry, interfaces or code that may be operable to send or receive control signals to one or more of the AFM chips  100 , the AFM optical system  820  and the scanning stage  810 . The AFM controller  840  may comprise an arbitrary waveform generator  842  for providing signals to the MRD chip  100 , for example, to apply bias voltages to the MRD chip  100 . The AFM controller  840  may be operable to actuate motion of the tip  210  by sending signals to the resonator bars  230  or to the continuous resonator membrane  530 , for example, utilizing changes in capacitance, piezo-resistive or piezo-strain techniques. The AFM controller  840  may comprise a data acquisition system  843  that may be operable to convert received signals into data that can be stored in a memory device or utilized by a computer, for example, the one or more memory devices  852  and/or the AFM computing device  850 . In some systems, the data acquisition system  843  may receive signals generated by detection of displacement of the resonator bars  230  or of the continuous resonator membrane  530 . For example, the data acquisition system  843  may convert voltage signals received generated from measurements of light deflection, into numerical data. 
     In some systems, the sample  130  may be placed on the scanning stage  810 . The scanning stage  810  may be operable to move the sample  130  relative to the tip  210  of the MRD chip  100  to enable testing of the sample  130  surface at various positions. For example, the scanning stage  810  may enable raster scanning of the sample  130  by the tip  210 . 
     The AFM optical system  820  may comprise one or more devices that may be communicatively coupled to the controller  840  and/or the computing device  850 . The one or more AFM optical system  820  devices may enable detection of changes in sample  130 , detection of tip  210  deflection, data collection, observation of the MRD chip  110  and/or sample  130 , or heating of the MRD chip  100  and/or the sample  130 . 
     In one example, the AFM optical system  820  may comprise a laser, a lens and/or a photodetector or interferometer for measuring displacement or frequency of the resonator bars  230  or the continuous resonator membrane  530 . In this regard, the laser may be aimed at the resonators  230  or  530  through the lens and changes in reflected beam angles may be measured in the photo detector and communicated to the AFM computing device  850  and/or the controller  840 . 
     In another example, the AFM optical system  820  may comprise an optical microscope that may enable visual observation of the sample  130 , the tip  210  and/or the cantilever  220 . In some systems, the optical microscope may provide video images, for example, during testing of the sample  130 . 
     In some systems, the AFM optical system  820  may comprise a laser that may be utilized for photo-thermal heating of the sample  130  and/or the tip  210 . 
     In some systems, an external arbitrary waveform generator and/or an external data acquisition module (not shown) may be utilized to control testing operations of the sample  130  utilizing the MRD chip  100  and/or measure results. These external modules may be utilized in conjunction with one or more elements of the AFM system  800  or may function independently. 
     In operation, the AFM computing device  850  may execute instructions that may control configuration of the test set-up in the AFM system  800 , perform testing operations and/or control data acquisition via the AFM controller  840 , for example. The AFM controller  840  may communicate with the AFM optical system  820 , the MRD chip  100  and/or the scanning stage  810  to generate and/or measure various forces and/or changes in properties of the sample  130 . The AFM controller may actuate motion of the sample  130  relative to the tip  210  via the scanning stage  810  and/or may read test results as the tip  210  is scanned over the sample surface. The AFM controller  840  may actuate tip  210  and cantilever  220  motion relative to the sample  130 , by applying AC and/or DC voltages to the MRD chip  100  and exciting resonant vibrations in one or more of the resonator bars  230  or the continuous resonator membrane  530 . The AFM controller  840  and/or the computing device  850  may receive signals from the MRD chip  100  via one or more of the resonator bars  230 , the continuous resonator membrane  530  and/or the AFM optical system  820  that may indicate the frequencies of vibration of the tip  210 . In this manner, the AFM system  800  may utilize the MRD chip  100  to determine forces and/or changes in properties of the sample  130 . 
     A multi-resonant detection system for atomic force microscopy (AFM) may comprise: 
     a. an AFM chip;
 
b. a microcantilever supported by the AFM chip;
 
c. an AFM tip supported by the microcantilever;
 
d. either (1) an array of varying-frequency micro-resonators OR (2) a continuous resonance membrane supported by the AFM chip and disposed in an operable relationship with the cantilever so that:
 
     i. at least one of the micro-resonators mechanically amplifies the motion of the microcantilever; 
     ii. the amplified vibration of the micro-resonator can be read by an atomic force microscope to generate a measurement signal. 
     iii. (optional) microcantilever can be used as a driver to drive tip motion. 
     The AFM chip may provide a shield to protect the resonator array from various environmental conditions. 
     A computing and/or communication system may include one or more computing apparatuses to execute a series of commands representing the method steps described herein. The computing and/or communication system may include a cloud computing environment, which may allow the one or more computing apparatuses to communicate and share information through a wired or wireless network. The one or more computing apparatuses may comprise a mainframe, a super computer, a PC or Apple Mac personal computer, a hand-held device, a smart phone, or any other apparatus having a central processing or controller unit known in the art. Each computing apparatus may be programmed with a series of instructions that, when executed, may cause the computer to perform the method steps as described and claimed in this application. The instructions that are performed may be stored on a machine-readable data storage device and may be carried out by the processing unit or controller. 
     The machine-readable data storage device may be a portable memory device that may be readable by each computing apparatus. Such portable memory device may be a compact disk (CD), digital video disk (DVD), a Flash Drive, any other disk readable by a disk driver embedded or externally connected to a computer, a memory stick, or any other portable storage medium currently available or yet to be invented. Alternately, the machine-readable data storage device can be an embedded component of a computing apparatus such as a hard disk or a flash drive. 
     The computing apparatus and machine-readable data storage device can be a standalone device or a device that is imbedded into a machine or other system, such as a cloud, that uses the instructions for a useful result. 
     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.