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The inchworm motor is a device that uses piezoelectric actuators to move a shaft with nanometer precision.
In its simplest form, the inchworm motor uses three piezo-actuators (2 and 3, see Figure 1.) mounted inside a tube (1) and electrified in sequence to grip a shaft (4) which is then moved in a linear direction. Motion of the shaft is due to the extension of the lateral piezo (2) pushing on two clutching piezos (3).
The actuation process of the inchworm motor is a six-step cyclical process after the initial relaxation and initialization phase. Initially, all three piezos are relaxed and unextended. To initialize the inchworm motor the clutching piezo closest to the direction of desired motion (which then becomes the forward clutch piezo) is electrified first then the six-step cycle begins as follows (see Figure 2.):
Step 1. Extension of the lateral piezo.
Step 2. Extension of the aft clutch piezo.
Step 3. Relaxation of the forward clutch piezo.
Step 4. Relaxation of the lateral piezo.
Step 5. Extension of the forward clutch piezo.
Step 6. Relaxation of the aft clutch piezo.
Electrification of the piezo actuators is accomplished by applying a high bias voltage to the actuators in step according to the "Six Step" process described above. To move long distances the sequence of six steps is repeated many times in rapid succession. Once the motor has moved sufficiently close to the desired final position, the motor may be switched to an optional fine positioning mode. In this mode, the clutches receive constant voltage (one high and the other low), and the lateral piezo voltage is then adjusted to an intermediate value, under continuous feedback control, to obtain the desired final position.
The non-powered behaviour of this piezoelectric motor is one of two options: normally locked or normally free. A normally free type allows free movement when unpowered but can still be locked by applying a voltage.
The inchworm motor is commonly used in scanning tunneling microscopes (STMs). An STM requires nanometer-scale control of its scanning tip near the material it is observing. This control can be accomplished by connecting the scanning tip to the shaft of the inchworm motor. The inchworm motor in turn allows control in a direction normal to the plane of the observed material's surface. Movement across the surface is commonly referred to as movement in the x-y plane, whereas movement normal to the surface is commonly referred to as movement in the z-direction. Movement of the scanning tip by the inchworm motor is either manually controlled or automatically controlled by connecting the motor to a feedback system.
The inchworm motor can be used in patch clamping of biological cells. This technique is most often performed with an optical microscope and a micromanipulator holding a glass pipette. The inchworm motor is particularly ideal in patch clamping because it provides the operator with virtually an instantaneous, precise, smooth and predictable motion without drift.
Piezoelectricity is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure and latent heat. It is derived from Ancient Greek πιέζω (piézō) 'to squeeze or press' and ἤλεκτρον (ḗlektron) 'amber'. The German form of the word (Piezoelektricität) was coined in 1881 by the German physicist Wilhelm Gottlieb Hankel; the English word was coined in 1883.
A scanning tunneling microscope (STM) is a type of scanning probe microscope used for imaging surfaces at the atomic level. Its development in 1981 earned its inventors, Gerd Binnig and Heinrich Rohrer, then at IBM Zürich, the Nobel Prize in Physics in 1986. STM senses the surface by using an extremely sharp conducting tip that can distinguish features smaller than 0.1 nm with a 0.01 nm (10 pm) depth resolution. This means that individual atoms can routinely be imaged and manipulated. Most scanning tunneling microscopes are built for use in ultra-high vacuum at temperatures approaching absolute zero, but variants exist for studies in air, water and other environments, and for temperatures over 1000 °C.
Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very-high-resolution type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit.
Ball bonding is a type of wire bonding, and is the most common way to make the electrical interconnections between a bare silicon die and the lead frame of the package it is placed in during semiconductor device fabrication.
A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, measurement, and control systems, where electrical signals are converted to and from other physical quantities. The process of converting one form of energy to another is known as transduction.
An actuator is a component of a machine that produces force, torque, or displacement, when an electrical, pneumatic or hydraulic input is supplied to it in a system. The effect is usually produced in a controlled way. An actuator translates such an input signal into the required form of mechanical energy. It is a type of transducer. In simple terms, it is a "mover".
Scanning probe microscopy (SPM) is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. SPM was founded in 1981, with the invention of the scanning tunneling microscope, an instrument for imaging surfaces at the atomic level. The first successful scanning tunneling microscope experiment was done by Gerd Binnig and Heinrich Rohrer. The key to their success was using a feedback loop to regulate gap distance between the sample and the probe.
A piezoelectric motor or piezo motor is a type of electric motor based on the change in shape of a piezoelectric material when an electric field is applied, as a consequence of the converse piezoelectric effect. An electrical circuit makes acoustic or ultrasonic vibrations in the piezoelectric material, most often lead zirconate titanate and occasionally lithium niobate or other single-crystal materials, which can produce linear or rotary motion depending on their mechanism. Examples of types of piezoelectric motors include inchworm motors, stepper and slip-stick motors as well as ultrasonic motors which can be further categorized into standing wave and travelling wave motors. Piezoelectric motors typically use a cyclic stepping motion, which allows the oscillation of the crystals to produce an arbitrarily large motion, as opposed to most other piezoelectric actuators where the range of motion is limited by the static strain that may be induced in the piezoelectric element.
Scanning tunneling spectroscopy (STS), an extension of scanning tunneling microscopy (STM), is used to provide information about the density of electrons in a sample as a function of their energy.
A linear actuator is an actuator that creates linear motion, in contrast to the circular motion of a conventional electric motor. Linear actuators are used in machine tools and industrial machinery, in computer peripherals such as disk drives and printers, in valves and dampers, and in many other places where linear motion is required. Hydraulic or pneumatic cylinders inherently produce linear motion. Many other mechanisms are used to generate linear motion from a rotating motor.
An ultrasonic motor is a type of piezoelectric motor powered by the ultrasonic vibration of a component, the stator, placed against another component, the rotor or slider depending on the scheme of operation. Ultrasonic motors differ from other piezoelectric motors in several ways, though both typically use some form of piezoelectric material, most often lead zirconate titanate and occasionally lithium niobate or other single-crystal materials. The most obvious difference is the use of resonance to amplify the vibration of the stator in contact with the rotor in ultrasonic motors. Ultrasonic motors also offer arbitrarily large rotation or sliding distances, while piezoelectric actuators are limited by the static strain that may be induced in the piezoelectric element.
Nanotribology is the branch of tribology that studies friction, wear, adhesion and lubrication phenomena at the nanoscale, where atomic interactions and quantum effects are not negligible. The aim of this discipline is characterizing and modifying surfaces for both scientific and technological purposes.
Near-field scanning optical microscopy (NSOM) or scanning near-field optical microscopy (SNOM) is a microscopy technique for nanostructure investigation that breaks the far field resolution limit by exploiting the properties of evanescent waves. In SNOM, the excitation laser light is focused through an aperture with a diameter smaller than the excitation wavelength, resulting in an evanescent field on the far side of the aperture. When the sample is scanned at a small distance below the aperture, the optical resolution of transmitted or reflected light is limited only by the diameter of the aperture. In particular, lateral resolution of 6 nm and vertical resolution of 2–5 nm have been demonstrated.
Scanning ion-conductance microscopy (SICM) is a scanning probe microscopy technique that uses an electrode as the probe tip. SICM allows for the determination of the surface topography of micrometer and even nanometer-range structures in aqueous media conducting electrolytes. The samples can be hard or soft, are generally non-conducting, and the non-destructive nature of the measurement allows for the observation of living tissues and cells, and biological samples in general.
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Amplified piezoelectric actuators are specific actuators using piezoelectric materials as active material and have a specific design to overcome traditional limitations of classical direct piezoelectric actuators, the limited stroke. As classical piezoelectric materials have a strain of 0.1%, it is practically impossible to reach significant stroke without displacement amplification. The solution to reach middle range stroke is to use an amplification system.
Piezoresponse force microscopy (PFM) is a variant of atomic force microscopy (AFM) that allows imaging and manipulation of piezoelectric/ferroelectric materials domains. This is achieved by bringing a sharp conductive probe into contact with a ferroelectric surface and applying an alternating current (AC) bias to the probe tip in order to excite deformation of the sample through the converse piezoelectric effect (CPE). The resulting deflection of the probe cantilever is detected through standard split photodiode detector methods and then demodulated by use of a lock-in amplifier (LiA). In this way topography and ferroelectric domains can be imaged simultaneously with high resolution.
Photoconductive atomic force microscopy (PC-AFM) is a variant of atomic force microscopy that measures photoconductivity in addition to surface forces.
The single-molecule electric motor is an electrically operated synthetic molecular motor made from a single butyl methyl sulphide molecule. The molecule is adsorbed onto a copper (111) single-crystal piece by chemisorption. The motor, the world's smallest electric motor, is just a nanometer across. It was developed by the Sykes group and scientists at the Tufts University School of Arts and Sciences and published online September 4, 2011.
Multi-tip scanning tunneling microscopy extends scanning tunneling microscopy (STM) from imaging to dedicated electrical measurements at the nanoscale like a ″multimeter at the nanoscale″. In materials science, nanoscience, and nanotechnology, it is desirable to measure electrical properties at a particular position of the sample. For this purpose, multi-tip STMs in which several tips are operated independently have been developed. Apart from imaging the sample, the tips of a multi-tip STM are used to form contacts to the sample at desired locations and to perform local electrical measurements.