JP2007044804A - Nano tweezers device and method for gripping micro sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nano tweezer device capable of accurately grasping and releasing a minute object.
SOLUTION: The fixed electrodes 5a and 5b and the movable electrodes 6a and 6b constituting the electrostatic actuators 4a and 4b of the nanotweezers 1 each have a comb shape so that a plurality of comb teeth mesh with each other. Opposed. The fixed electrodes 5 a and 5 b are fixed to the pedestal 10, and the movable electrodes 6 a and 6 b are elastically fixed to the pedestal 10 by a thin beam-shaped support portion 7. When a DC voltage is applied between the fixed electrodes 5a, 5b and the movable electrodes 6a, 6b by the power supply circuit 2, the movable electrodes 6a, 6b move by the Coulomb force to drive the arm 3. In the nano tweezer device 50, the electrostatic actuators 4a and 4b are locked, so that a minute object can be reliably gripped.
[Selection] Figure 1

Description

  The present invention relates to a nanotweezers device that grips and releases a micro object using an electrostatic force, and a micro sample gripping method.

  The nano tweezers has a function of gripping, transferring, and releasing a nano-sized or micron-sized micro object by opening and closing operations of the tip portions of a pair of arms. Conventionally, various actuators such as an electrostatic system, a thermal system, and a piezoelectric system have been proposed as actuators for opening and closing a pair of arms. Among them, electrostatic actuators that use two interdigitated electrodes are known, and the arm is opened and closed by on / off control of the voltage applied between the electrodes. (For example, refer to Patent Document 1). Furthermore, in the apparatus described in Patent Document 1, the arm is opened and closed by a predetermined amount using a reciprocating carrier.

JP-A-7-52072

  However, in the apparatus described in Patent Document 1, it is difficult to determine whether or not the minute object has been correctly grasped when grasping the minute object. Further, when releasing a grasped minute object, there is a problem that it is difficult to accurately perform the releasing operation because the transition process from the grasping state to the releasing state cannot be checked.

(1) A nanotweezer device according to an invention of claim 1 is a pair of arms that can be opened and closed, an electrostatic actuator that opens and closes the pair of arms with Coulomb force, and a control that applies a predetermined drive voltage to the electrostatic actuator. The control means is configured such that after the pair of arms grips the object, the Coulomb force generated by the electrostatic actuator exceeds the maximum elastic force generated by the deformation of the arm when gripping the object. The lock driving voltage determined in (1) is applied to the electrostatic actuator.
(2) The invention according to claim 2 is the nanotweezer device according to claim 1, wherein the control means is configured such that the Coulomb force generated by the electrostatic actuator is elastic after the pair of arms grips the object by the lock driving voltage. An unlock driving voltage determined so as to balance the force is applied to the electrostatic actuator.
(3) A third aspect of the present invention is the nanotweezer device according to the first or second aspect, wherein when the control means grips the object with the pair of open arms, the pair of arms holds the predetermined grip. A grip driving voltage determined to grip a symmetrical object with force is applied to the electrostatic actuator.
(4) The invention of claim 4 is the nanotweezer device according to any one of claims 1 to 3, wherein a lock switch for instructing application of a lock drive voltage and an unlock switch for instructing an unlock drive voltage And a grip switch for instructing a grip driving voltage is provided with an operation panel arranged to be operated by an operator.
(5) The invention according to claim 5 is the nanotweezer device according to any one of claims 1 to 4, wherein the electrostatic actuator includes a comb-shaped fixed electrode and a predetermined interval between the fixed electrode. And a comb-shaped movable electrode that meshes with each other.
(6) A sixth aspect of the present invention is the nanotweezer device according to the fifth aspect, wherein an insulating layer is provided on an opposing surface of at least one of the comb teeth of the fixed electrode and the comb teeth of the movable electrode.
(7) In the method of gripping a micro sample according to the invention of claim 7, the Coulomb force is deformed when the object is gripped after the pair of arms grips the object by the electrostatic actuator that is opened and closed by the Coulomb force. A drive voltage is applied to the electrostatic actuator so as to exceed the elastic force of the arm.

  According to the nanotweezer device of the present invention, a minute object can be reliably gripped by applying a lock driving voltage to the electrostatic actuator.

Hereinafter, a nanotweezer device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing an outline of the entire nanotweezers according to an embodiment of the present invention. The nano tweezers device 50 includes a nano tweezers 1 and a power supply circuit 2. The nano tweezers 1 are integrally manufactured from an SOI (Silicon on Insulator) wafer as will be described later. The SOI wafer is obtained by forming a SiO ₂ layer on one of _two Si single crystal plates and bonding them together via the SiO ₂ layer.

  As shown in FIG. 1, the nanotweezers 1 includes a pair of arms 3a and 3b, a pair of electrostatic actuators 4a and 4b, a pair of support portions 7a and 7b, a pair of connecting portions 8a and 8b, and a pair of Arm support portions 9a and 9b and a pedestal 10 are provided. The electrostatic actuator 4a is provided with a fixed electrode 5a and a movable electrode 6a, and the electrostatic actuator 4b is provided with a fixed electrode 5b and a movable electrode 6b. The pedestal 10 is detachably attached to a holder (not shown), and the holder can be moved in a three-dimensional direction by a moving mechanism (not shown), whereby the entire nanotweezers 1 can be moved in a three-dimensional direction. ing.

  The structure of the nanotweezers 1 will be described in detail with reference to FIG. FIG. 2 is an enlarged plan view showing the nanotweezers 1 shown in FIG. In FIG. 2 and subsequent figures, the components provided symmetrically of the nanotweezers 1 will be described mainly only on the left side. Both the fixed electrode 5a and the movable electrode 6a have a comb-teeth shape, and are arranged to face each other so that a plurality of comb teeth are engaged with each other. Although the fixed electrode 5a is fixed to the pedestal 10, the movable electrode 6a is elastically fixed to the pedestal 10 by a thin beam-like support portion 7a. The arms 3a and 3b are elastically fixed to the pedestal 10 via thin beam-like arm support portions 9a and 9b, respectively. The arm 3a and the movable electrode 6a are connected by a connecting portion 8a, and the arm 3b and the movable electrode 6b are connected by a connecting portion 8b.

  1 and 2, the nano tweezers 1 includes a left electrode terminal 2a, a left electrode terminal 2b, a left arm electrode terminal 2c, a right arm electrode terminal 2d, a right electrode terminal 2e, a right electrode terminal 2f and a ground. An electrode terminal 2g is formed. The left electrode terminal 2a is connected to the fixed electrode 5a, the left electrode terminal 2b is connected to the movable electrode 6a, and the left arm electrode terminal 2c is connected to the arm 3a. The right arm electrode terminal 2d is connected to the arm 3b, the right electrode terminal 2e is connected to the movable electrode 6b, the right electrode terminal 2f is connected to the fixed electrode 5b, and the ground electrode terminal 2g is connected to the base 10. These seven electrode terminals 2a to 2g and the seven terminals 2a to 2g of the power supply circuit 2 are connected to each other with corresponding signs.

  A DC power source 20a is connected between the left electrodes 2a and 2b, and a DC power source 20b is connected between the right electrodes 2e and 2f. By applying a DC voltage between the left electrodes 2a and 2b, an electrostatic attractive force due to Coulomb force can be generated between the fixed electrode 5a and the movable electrode 6a, and the movable electrode 6a can be moved with respect to the fixed electrode 5a. . The same operation is performed for the right fixed electrode 5b and the movable electrode 6b. Reference numeral 200 denotes a controller that controls the DC power sources 20a and 20b, which will be described in detail later.

  The left arm electrode terminal 2c and the right arm electrode terminal 2d are provided to detect the amount of electricity acting between the arms 3a and 3b. Therefore, the arms 3a and 3b are insulated from the movable electrodes 6a and 6b, respectively. The ground electrode terminal 2g is provided to prevent the base 10 from becoming a floating electrode. The chip resistors R <b> 1 to R <b> 6 are provided in order to prevent noise from being mixed due to contact of the human body with the nanotweezers 1 or reception of electromagnetic waves from the cable connecting the nanotweezers 1 and the power supply circuit 2.

  FIG. 3 is a plan view showing a main part of the nanotweezers 1 shown in FIG. When a voltage is applied between the movable electrode 6a and the fixed electrode 5a, the movable electrode 6a moves in the right direction (x direction) in FIG. 3 with respect to the fixed electrode 5a, thereby driving the arm 3a in the x direction. . When the voltage application is released, the arm 3a returns to the original position, that is, the position shown in FIG. The operation is only reversed on the right side. Similarly, the movable electrode 6b moves leftward in the figure with respect to the fixed electrode 5b, whereby the arm 3b is driven leftward. Therefore, the arm interval D can be changed, and a minute object can be grasped or released.

Here, the operation principle of the electrostatic actuator 4a will be described.
FIG. 4 is a perspective view schematically showing a part of the fixed electrode 5a and the movable electrode 6a of the nanotweezers 1. FIG. The arm spacing D in the initial state of the applied voltage V = 0 and D _0. In a typical model of comb teeth type electrostatic actuator, the electrostatic capacitance C _comb (x) generated between the fixed electrode 5a and the movable electrode 6a of the formula as a function of the moving distance x from the initial position of the movable electrode 6a It is given by (1). However, in Formula (1), ε ₀ is the dielectric constant of vacuum, w is the width of the comb teeth, l ₀ is the initial distance between the tip of the comb teeth and the wall of the electrode facing, l is the length of the comb teeth, and g is The gap between the comb teeth, b is the thickness of the comb teeth, V is the applied voltage, and N is the number of comb teeth, which are shown in comparison with FIG.

At this time, the movable electrode 6a, the energy stored between the fixed electrodes 5a is because C _comb (x) V ^2/2, Coulomb force generated between the electrodes (electrostatic force) F _comb (x) is given by Equation (2) It is done.

  Next, the elastic force when the arm 3a moves so as to close from the initial position will be described. As shown in FIG. 2, the arm 3a and the movable electrode 6a are integrated by a connecting portion 8, and they are elastically supported by a support portion 7a and an arm support portion 9a. However, since the elastic force of the arm support portion 9a is relatively small with respect to the elastic force of the support portion 7a, the following description will be made ignoring the elastic force of the arm support portion 9a.

When the pair of support portions 7a provided on the movable electrode 6a is regarded as a cantilever beam and the general formula of the stress derived from the Mole's theorem is used, the elastic force F _el (x) of the support portion 7a is expressed by the movable electrode 6a. As a function of the movement distance x of In the formula (3), L is the length of the support portion 7a, B the width of the support portion 7a, h is the thickness of the support portion 7a, E (GPa) is a modulus of transverse elasticity of the silicon, _{N s} is the support portion 7a Is a number.

If the moving distance of the movable electrode 6a when the left and right arms 3a and 3b contact each other and the arm interval D becomes 0 is xd, the elastic force F _{e l} ( x) holds in the range of 0 ≦ x <xd. When the movable electrode 6a further moves and the arms 3a and 3b are deformed after the arm interval D becomes 0, the elastic force due to the deformation of the arms 3a and 3b is added to the F _{e l} (x). . At this time, assuming that the arms 3a and 3b are cantilever structures (spring constant is k) from the arm tip to the force point of the connecting portion 8, the elastic force due to the deformation of the arms 3a and 3b is k (x− xd), and in the range of xd ≦ x < ₁₀ , it is expressed as in equation (4). l ₀ is the initial value of the gap between the tip of the comb teeth and the valley, and when x = l ₀ , the gap is zero.

Figure 5 is a Coulomb force F _comb (x) represented by the formula (2), Equation (3), the elastic force represented by (4) F _{e l} (x), in the moving distance of the movable electrode 6a This is shown for a certain comb tooth movement distance x. In FIG. 5, the vertical axis represents the Coulomb force or the elastic force, and the horizontal axis represents the comb tooth movement distance x.

  Curves C1 and C2 indicate the Coulomb force when the applied voltage is V1, V2 (V2> V1), the straight line portion E1 indicates the elastic force according to the equation (3), and the straight line portion E2 indicates the elastic force according to the equation (4). Show. As described above, xd is the moving distance when the arms 3a and 3b are in contact with each other. When x> xd, the elastic force due to the deformation of the arms 3a and 3b is applied. Is also getting bigger.

<Operation description>
Next, the opening / closing operation of the nanotweezers 1 will be described. As described above, the movable electrode 6a and the arm 3a integrated by the connecting portion 8a are elastically supported by the support portion 7a and the arm support portion 9a. Therefore, when a voltage is applied to the electrodes 5a and 6a, the arm 3a is forced to close by the Coulomb force (see formula (2)) acting between the electrodes, and the arm 3a is returned to the initial position against the Coulomb force. The movable electrode 6a and the arm 3a are moved to a position where the elastic force is balanced. However, here, as described above, the elastic force of the arm support portion 9a is ignored.

As the applied voltage increases, the comb tooth movement distance x increases and the arm interval D (see FIG. 3) decreases. The intersection of the curve C1 and the straight line portion E1 in FIG. 5 represents the position where the Coulomb force and the elastic force are balanced when the applied voltage is V1, and the comb tooth movement distance is xa as shown in FIG. Thus, the arm interval is (D ₀ -2xa). D ₀ is an initial value of the arm interval when the comb tooth movement distance x is x = 0.

  FIG. 6 is a diagram showing the relationship between the applied voltage V and the comb movement distance x. When the applied voltage V is gradually increased from 0, the comb tooth movement distance x is increased by moving from the left end to the right direction on the curve F1. As described above, the comb tooth movement distance becomes xa at the applied voltage V1, and when the applied voltage is increased to V3, the comb tooth movement distance becomes xd and the arms 3a and 3b come into contact with each other as shown in FIG. . When the applied voltage is further increased, the movable electrodes 6a and 6b move while deforming the arms 3a and 3b as shown in FIG. At this time, since an elastic force is applied due to the deformation of the arms 3a and 3b, the movement distance change tendency with respect to the voltage change changes before and after x = xd.

  In FIG. 5, when the applied voltage is gradually increased, the curve indicating the Coulomb force increases toward the right and moves upward in the figure. Therefore, the intersection between the curve of the Coulomb force and the straight line portions E1 and E2 related to the elastic force moves to the right. That is, the rightward movement of the intersection as the applied voltage V increases corresponds to the rightward movement on the curve F1 in FIG.

(Explanation about pull-in)
By the way, when the applied voltage is further increased to V2, it is always above the straight line portions E1 and E2 as shown by a curve C2 in FIG. That is, the Coulomb force always exceeds the elastic force at any comb tooth movement distance x (Coulomb force> elastic force), and the movable electrode 6 becomes the fixed electrode 5a without further increasing the applied voltage. It is brought into close contact as shown in FIG. Such a phenomenon is called a pull-in phenomenon.

The voltage at which such a pull-in phenomenon occurs is a voltage V _p at which the contact between the curve of the Coulomb force and the linear portions E1 and E2 of the elastic force disappears. Here, the voltage V _p is referred to as a lock voltage. In the present embodiment, in order to prevent short circuit between fixed electrode 5a and movable electrode 6a during pull-in, an insulating layer having a thickness of about 70 nm is formed on the surfaces of fixed electrode 5a and movable electrode 6a. Yes. In this case, the fixed electrode 5a and the movable electrode 6a are in a pull-in state at a distance of about 140 nm. The Coulomb force acting at this time can be obtained by using the dielectric constant of an insulating layer (for example, a silicon oxide film) instead of the vacuum dielectric constant ε ₀ in Equation (2). The relative dielectric constant of the silicon oxide film is about 4.2.

6, when gradually increased to V _p applied voltage V from V3, comb teeth travel x moves to xb from xd. When the applied voltage reaches the lock voltage V _p, the movable electrode 6a is brought into close contact with the fixed electrode 5a rapidly moved from xb to xp. The movement distance xp of pull state is equal to the initial distance l ₀ of comb electrodes.

Arms 3a immediately before the applied voltage is V _p, the gripping force of 3b, the arms deformation amount is a resilient force corresponding to (xb-xd), arm deformation amount becomes a pull state (V = V _p) (xp -Xd), the increase in elastic force is equal to the force required to further deform the arms 3a, 3b by (xp-xb). That is, the gripping force can be greatly increased with a slight voltage increase. Arms 3a, the structure is elastic force caused by 3b is deformed, there is an upper limit, when the applied voltage V _p, the Coulomb force, the upper limit value (maximum elastic force generated by the arm 3a, 3b are deformed) Is over. The gripping force described above is a value when the sample is not gripped between the arms 3a and 3b as shown in FIG. 18B, and when the sample is gripped, it varies depending on the size of the sample.

  In this way, in the pull-in state, the movable electrode 6a is in close contact with the fixed electrode 5a by a large Coulomb force and is in a fixed state. Therefore, it can be considered that the electrodes 5a and 6a are integrated. As a result, the nanotweezers 1 can continue to hold the sample stably even if vibrations accompanying conveyance or external impacts are applied, and the reliability of sample conveyance can be remarkably improved. it can. Further, once in the pull-in state, friction is generated between the movable electrode 6a and the fixed electrode 5a, so that it is difficult to move in the direction perpendicular to the protruding direction of the comb teeth.

(Explanation about pull-out)
Next, the pull-in state release operation will be described. To release the pull condition, it is sufficient to decrease the applied voltage which is a lock voltage V _p. When the actually decrease the applied voltage from V _p, the applied voltage as shown in the straight line F2 in FIG. 6 is continued pull state until V _r, the movable electrode 6a is kept in close contact with the fixed electrode 5a. When the applied voltage becomes V _r , the pull-in state is released, and the movable electrode 6a moves to the comb movement distance xr where the elastic force and the Coulomb force at the applied voltage V _r are balanced. In the example shown in FIG. 6, since xr <xd, the arms 3a and 3b are opened. In this case, it will be referred to as the voltage V _r and unlock voltage.

As described above, the following reasons can be considered as a cause of the difference between the voltage (lock voltage V _p ) at which the pull-in state is established and the voltage (unlock voltage V _r ) at which the pull-in state is released. Figure 7 is a diagram for explaining the unlocking voltage V _r, shows the relationship between the Coulomb force or the elastic force and the comb moving distance x. In FIG. 7, the region where the comb tooth movement distance x is small is not shown because it is not necessary for the description.

In FIG. 7, curve C (V _p ) shows the Coulomb force when the applied voltage is the lock voltage V _p , and curve C (V _r ) shows the Coulomb force when the applied voltage is the unlock voltage V _r. ing. The curve C (V _r ) intersects the straight line portion E1 at the comb tooth movement distance xr. Curve C (V4) shows the Coulomb force when the applied voltage _V4, a _V p>V4> V _r.

As described above, the insulating layer is formed on the surface of the fixed electrode 5a and the movable electrode 6a so that the electrodes 5a and 6a are not short-circuited in the pull-in state. Further, since the contact surfaces of the electrodes 5a and 6a are not ideal planes and have minute irregularities, the distance between the electrodes 5a and 6a is not strictly zero in the pull-in state. For this reason, even in the pull-in state, a gap corresponding to the thickness Δx0 of the insulating layer is formed between the electrodes 5a and 6a. That is, the comb tooth movement distance xp in the pull-in state is xp = l ₀ −Δx ₀ .

If there is no insulating layer and the fixed electrode 5a and the movable electrode 6a are in close contact with each other, the comb tooth movement distance x is x = ₁₀ , so that even a slight voltage is applied to the electrodes 5a and 6a. Thus, the coulomb force becomes infinite at x = l ₀ in the pull-in state. However, in actuality, there are irregularities and natural oxide films on the contact surface, and the insulating layer is formed as described above, so the Coulomb force does not become infinite even in the pull-in state.

For example, in the example shown in FIG. 7, since an insulating layer having a thickness Δx0 is formed, even in the pull-in state (x = xp), curves C (V _p ), C (V 4), C (V _r ) The Coulomb force shown by is not infinite. At this time, considering the case where reduced from pull state of the lock voltage V _p applied voltage V to V4, as can be seen from the Coulomb force curve C in FIG. 7 (V4), Coulomb force in comb tooth movement distance xp > It is elastic force. Therefore, the movable electrode 6a is not separated from the fixed electrode 5a, and the pull-in state is maintained.

However, further lowering the applied voltage V and V = V _r, the position of the Coulomb force curve C (V _r) in comb tooth movement distance xp is a lower than the linear portion E2 which represents the elastic force, Coulomb force <It becomes elastic force. As a result, the arms 3a and 3b are driven by the elastic force in the opening direction to return to the comb movement distance xr, and the Coulomb force and the elastic force are balanced at that position. That is, the pull-in state of the movable electrode 6a is released and the unlocked state is established, and the arms 3a and 3b are opened.

  In this way, by controlling the applied voltage V, the arms 3a and 3b can be opened / closed, pulled in and released. By the way, as shown in FIG. 6, the moving amount of the movable electrode 6a at the time of pull-in is (xp-xb), and the gripping force increment at the time of pull-in can be adjusted by adjusting the film thickness Δx0 of the insulating layer. it can. Further, by increasing the film thickness Δx0 of the insulating layer, it is possible to reduce the moving amount (xp−xr) of the movable electrode 6a when pull-in is canceled.

For example, when the thickness of the insulating layer in FIG. 7 is increased as (l ₀ −xc), the deformation increase (xp−xc) of the arms 3a and 3b during pull-in is the deformation increase in the case of the film thickness Δx0. = Smaller than xp-xd. As a result, the increase in gripping force in the pull-in state can be reduced, and it is suitable for samples that do not want to be gripped strongly, such as biological samples.

Decreasing the applied voltage and the lock voltage V _p to V = V4, the position of the Coulomb force curve C (V4) becomes the lower side of the linear portion E2 which represents the elastic force, the coulomb force <elastic force. As a result, the arms 3a and 3b are driven in the opening direction by the elastic force and returned to the comb movement distance xe, and the Coulomb force and the elastic force are balanced at that position. In the case of film thickness = l ₀ −xp described above, pull-in cannot be canceled unless the applied voltage is lowered to V _r , but in the case of film thickness = l ₀ −xc (> l ₀ −xp) The amount of applied voltage reduction required for the above can be reduced. Furthermore, the amount of movement of the movable electrode when pull-in is released can be reduced. In the case of FIG. 7, since xe> xd, the arms 3a and 3b are not opened.

  In the above-described example, the pull-in release can be performed with a higher applied voltage by increasing the film thickness of the insulating layer. However, a stopper structure is provided on a part of the plurality of comb teeth to actually make contact when pulling in. The number of comb teeth (ie, pull-in comb teeth) may be reduced. FIG. 19 shows an example of such a comb-tooth actuator, and shows a trapezoidal fixed electrode 25a and a movable electrode 26a. At the time of pull-in, the comb teeth 250 formed on the fixed electrode 25a are in close contact with the stopper portion 260 provided at the valley of the movable electrode 26a, and the other comb teeth 251 are in contact with the valley of the movable electrode 26a. There will be a gap between them. The stopper portion 260 may be provided by forming an insulating layer, for example, silicon oxide, in the valley portion of the movable electrode 26a, or the stopper portion 260 may be formed by inserting a structure from the outside into the valley portion of the movable electrode 26a. It may be provided.

If the thickness of the stopper portion 260 in the groove depth direction is t2, the gap dimension of the comb teeth 251 is also t2. Since the comb teeth have a trapezoidal shape, when the movable electrode 26a moves, the comb tooth interval g, which is the interval between the side surfaces of the comb teeth, also changes, and the comb tooth interval g becomes a function g (x) of the comb tooth movement distance x. Here, when the comb tooth interval in the pull-in state is gx3 and the comb tooth interval when the applied voltage is off is g0, the function g (x) is given by the following equation (5).

When the number of comb teeth 250 is N1, and the number of comb teeth 251 is N2, the Coulomb force Fcom2 (x) is given by the following equation (6). In equation (6), w2 is the width of the tip of the trapezoidal comb teeth, and θ is the inclination angle of the side surfaces of the comb teeth (see FIG. 19). If θ = 0 and g0 = gx3 in equation (6), the equation for a rectangular comb tooth is obtained.

  In the case of trapezoidal comb teeth, the width w2 of the tip of the comb that actually contributes to the Coulomb force is the width w of the rectangular comb teeth formed under the same conditions with respect to area, initial gap, comb tooth length, and comb tooth spacing. Smaller than that. However, as the moving distance increases, the comb tooth gap g becomes narrower and the inclination angle θ increases, so that the overlap of the comb teeth can be increased and the decrease in Coulomb force due to the decrease of w2 can be compensated. It becomes possible.

  Further, as shown in FIG. 20, the tips of the comb teeth of the fixed electrode 35a and the movable electrode 36a may be mountain-shaped to reduce the contact area in the pull-in state. In the example of FIG. 20, by making the stepped comb teeth, the gap g becomes narrower as the comb teeth move and become nested. In this case, since the rate of change of the gap is not uniform with respect to the change of the comb tooth movement distance x, the change of the Coulomb force changes greatly before and after the nested state.

  Note that the change of the applied voltage V during the above-described opening / closing operation may be performed manually, but in this embodiment, by operating a switch provided in the controller 200 shown in FIG. The operability can be improved by automatically changing the voltage necessary for releasing the pull-in. FIG. 21 is a diagram showing an operation panel of the controller 200, in which 201 is a power switch, 202 is an open switch, 203 is a lock / unlock switch, 204 is a grip switch, and 205 is a voltage adjustment dial.

  When the open switch 202 is operated, the applied voltage V is set to the open voltage, and the arms 3a and 3b are opened. Since the open voltage is set to zero volts in the initial state, it is in a fully open state. Normally, the open state is set according to the size of the target sample, and the applied voltage is adjusted by the voltage adjustment dial 205 from the fully open state so that an appropriate open state is obtained. Once the open voltage Vop is adjusted, when the open switch 202 is operated from the next time, the applied voltage is set to the open voltage Vop and a predetermined open state is established.

  Further, when the lock / unlock switch 203 is operated for the first time after the power is turned on, a lock operation is performed and a pull-in (locked) state is established. When the lock / unlock switch 203 is operated again, an unlock operation is performed and a pull-in release state is established. When the open switch 202 is operated in the pull-in state, the lock / unlock switch 203 is in an initial state immediately after the power is turned on. That is, when the lock / unlock switch 203 is operated again, the lock operation is performed.

When the grip switch 204 is operated after operating the open switch 202, the arms 3a and 3b are closed and the sample is gripped. In this case, the grip voltage Vg is set slightly higher than the applied voltage at which the arm interval is the same as the sample size so that the sample is gripped with a predetermined gripping force. Then, the pull-in state by applying a lock voltage V _p by operating the lock-unlock switch 203.

  After that, when the sample is transferred to a predetermined position by carrying the sample with the nano tweezers 1, the lock / unlock switch 203 is operated to release the pull-in state, and the open switch 202 is further operated to move the arms 3a and 3b. Open the sample and release the sample grip. As described above, in the pull-in state, the movable electrode 6a is firmly attached to the fixed electrode 5a, so that there is no possibility of dropping the sample due to vibration or the like during conveyance.

  As described above, by operating each switch of the controller 200, the transition between the open state, the grip state, the pull-in state (lock state), and the pull-in release state (unlock state) can be smoothly performed.

Next, with reference to FIGS. 8-16, the manufacturing method in the case of forming the nanotweezers 1 using an SOI substrate is demonstrated. The SOI substrate 100, the base layer 101, made of SiO ₂ insulating layer 102 made of <110> orientation of the single crystal silicon, as shown in FIG. 8 (a), the silicon layer 103 of monocrystalline silicon in the <110> orientation Are used in this order.

  As a material for forming the nanotweezers 1, not only an SOI substrate but also a substrate having a single crystal silicon layer on a glass substrate, an amorphous silicon substrate, a substrate having an SOI layer on a polysilicon substrate, or the like can be used. That is, if the uppermost layer is the silicon layer 103 having the <110> orientation and the substrate has a layer structure in which the insulating layer 102 is formed below the silicon layer 103, the base layer 101 is formed in a multilayer structure. It doesn't matter.

  An example of the thickness of each layer of the SOI substrate 100 will be described. The silicon layer 103 is 25 μm, the insulating layer 102 is 1 μm, and the base layer 101 is 300 μm. In addition, the region where one nanotweezer 1 is formed on the SOI substrate 100 has a rectangular shape of several millimeters both vertically and horizontally. In the step shown in FIG. 8A, an aluminum layer 104 having a thickness of about 50 nm is formed on the surface of the silicon layer 103 by sputtering or vacuum deposition.

  Next, as shown in FIG. 8B, a resist layer 105 having a thickness of about 2 μm is formed on the surface of the aluminum layer 104, and the resist layer 105 is exposed and developed by photolithography to obtain FIG. The resist pattern 105a shown in FIG. FIG. 11 is a perspective view of the SOI substrate 100, and a resist pattern 105 a corresponding to the arm 3, the electrostatic actuator 4, and the like is formed on the upper surface of the aluminum layer 104. In addition, FIG.8 (c) shows the II cross section of FIG.

  As shown in FIG. 8D, the aluminum layer 104 is etched with a mixed acid solution using the resist pattern 105a as a mask to expose the silicon layer 103. Thereafter, the silicon layer 103 is anisotropically etched in the vertical direction by ICP-RIE (Inductively Coupled Plasma-Reactive Ion Etching). This etching is performed until the insulating layer 102 is exposed. After the etching is completed, the resist pattern 105a and the aluminum layer 104 are removed with a sulfuric acid / hydrogen peroxide mixed solution (see FIG. 9A).

  FIG. 12 is a perspective view showing the SOI substrate 100 after the resist pattern 105a and the aluminum layer 104 are removed. A three-dimensional structure including the silicon layer 103 is formed on the insulating layer 102. The three-dimensional structure includes a portion 103a constituting the arm 3, a portion 103b constituting the electrostatic actuator 4, a portion 103c constituting the electrode terminals 2a to 2f, and a portion 103d constituting the guard. In addition, since a guard protects the arm 3 from damage at the time of manufacture and is not a component part of the nanotweezers 1, description of the formation process will be omitted below.

  As shown in FIG. 9B, a resist 106 is applied so as to cover the exposed insulating layer 102 and silicon layers 103 (103a to 103c). The coating thickness of the resist 106 is about 10 μm. Thereafter, the mask pattern is transferred to the resist 106 by photolithography and developed, thereby forming a resist pattern 106a from which the resist 106 at the tip of the arm constituent portion 103a is removed in a rectangular shape, as shown in FIG. Then, ICP-RIE, normal RIE, or the like is performed using the resist pattern 106a as a mask, and the tip portion of the arm component 103a is processed into a predetermined shape and size. It is also possible to machine the part into a predetermined shape and dimensions by mechanical cutting such as dicing.

  Next, as shown in FIG. 9C, the SOI substrate 100 is turned upside down, and an aluminum layer 107 is formed on the surface of the base layer 101 by sputtering or vacuum deposition. The thickness of the aluminum layer 107 is about 50 nm. Then, after forming a resist 108 on the aluminum layer 107 to a thickness of about 2 μm, a resist pattern is formed by photolithography, and the aluminum layer 107 is etched with a mixed acid solution using the resist 108 as a mask (FIG. 10). (See (a)).

  FIG. 14 is a perspective view showing the shapes of the resist 108 and the aluminum layer 107. FIG. 10A shows a cross section taken along the line II-II in FIG. 14, and a cross section of the arm portion 103 a formed of the silicon layer 103 is shown on the lower side (surface side) of the insulating layer 102. In the resist 108, a portion 111 corresponding to the connecting portion 8 and a portion 112 corresponding to the base 10 remain, and conversely, the peripheral region of the arm 3 is removed and the base layer 101 is exposed.

  Thereafter, the base layer 101 is etched by ICP-RIE using the resist 108 and the aluminum layer 107 formed on the base layer 101 as a mask. The base layer 101 is etched in the vertical direction by anisotropic etching, and the etching is performed until the insulating layer 102 is exposed. FIG. 10B also shows the II-II cross section of FIG. 14, and after the etching is completed, the resists 108 and 106 and the aluminum layer 107 are removed with a mixed solution of sulfuric acid and hydrogen peroxide.

  FIG. 15 is a view showing the back side of the base layer 101 shown in FIG. Etching forms the base 10, the connecting portion 8, and the like on the base layer 101. Next, the insulating layer 102 made of silicon oxide exposed on the pedestal 10 is etched using a buffered hydrogen fluoride solution. As a result, the insulating layer 102 is removed except for a region sandwiched between the silicon layer 103 and the base layer 101 (see FIG. 10C).

  FIG. 16 is a perspective view showing the surface side of the base layer 101, and FIG. 10C shows a III-III cross section of FIG. As described above, the insulating layer 102 is interposed between the silicon layer 103 and the base layer 101. After that, as shown in FIG. 10D, a conductor film 109 made of aluminum or the like is formed on the exposed base layer 101 and on the silicon layer 103 constituting each structure by a vacuum deposition method or the like. . The thickness of the conductor film 109 is 500 nm or less. In this way, the nanotweezers 1 are completed, but the arm 3 may be additionally processed by a processing apparatus such as FIB depending on the object to be grasped.

  In the correspondence between the embodiment described above and the elements of the claims, the power supply circuit 2 constitutes a control means. The present invention is not limited to the above-described embodiment as long as the characteristics are not impaired.

It is a lineblock diagram showing the outline of the whole nano tweezers device concerning an embodiment of the invention. It is a top view which expands and shows the nanotweezers 1 shown in FIG. It is a top view which shows the principal part of the nano tweezers 1 shown in FIG. 2 is a perspective view schematically showing a part of a fixed electrode 5a and a movable electrode 6a of the nanotweezers 1. FIG. It is a graph which shows the change of the Coulomb force and elastic force in the nano tweezers device concerning an embodiment. It is a graph which shows the relationship between the applied voltage V and the movement distance x of the movable electrode 6a in the nano tweezers which concern on embodiment. It is a figure explaining unlock voltage _Vr . It is a figure explaining the manufacturing process of the nano tweezers 1 concerning an embodiment, and a process progresses in order of Drawing 8 (a)-Drawing 8 (d). It is a figure which shows the process following FIG. 8, and a process progresses in order of Fig.9 (a)-FIG.9 (c). It is a figure which shows the process following FIG. 9, and a process progresses in order of Fig.10 (a)-FIG.10 (d). FIG. 9 is a perspective view of the SOI substrate 100 shown in FIG. FIG. 12 is a perspective view of SOI substrate 100 after removing resist pattern 105a and aluminum layer 104 shown in FIG. It is a perspective view of the SOI substrate 100 which shows the shape of the resist pattern 106a. FIG. 11 is a perspective view of an SOI substrate 100 showing the shapes of a resist pattern 108 and an aluminum layer 107 shown in FIG. It is a perspective view of the SOI substrate 100 which shows the back surface side of the base layer 101 shown in FIG.10 (b). It is a perspective view of the SOI substrate 100 which shows the surface side of the base layer 101 shown in FIG.10 (c). It is a figure which shows the relationship between the comb tooth movement distance and arms 3a and 3b, (a) shows the case where arms 3a and 3b are open, and (b) shows the state where arms 3a and 3b are closed. It is a figure which shows the relationship between the comb tooth movement distance and arm 3a, 3b, (a) shows the state before a pull-in, (b) shows the pull-in state. It is a figure which shows the fixed electrode 25a and the movable electrode 26a at the time of making the tooth | gear shape of an electrode into a trapezoid comb. It is a figure which shows the fixed electrode 35a at the time of setting the tooth | gear shape of an electrode to a step, and the movable electrode 36a. 2 is a diagram illustrating a controller 200. FIG.

Explanation of symbols

1: Nano tweezers 2: Power supply circuit 3a, 3b: Arm 4a, 4b: Electrostatic actuator 5a, 5b: Fixed electrode 6a, 6b: Movable electrode 7a, 7b: Support part 8a, 8b: Connection part 9a, 9b: Arm support Part 10: Pedestal 50: Nano tweezers 100: SOI wafer 101: Base layer 102: Insulating layer 103: Silicon layer 200: Controller 203: Lock / unlock switch 204: Grip switch

Claims (7)

A pair of arms that can be opened and closed;
An electrostatic actuator that opens and closes the pair of arms with Coulomb force;
Control means for applying a predetermined drive voltage to the electrostatic actuator,
The control means is configured so that after the pair of arms grips the object, a Coulomb force generated by the electrostatic actuator exceeds a maximum elastic force generated by the deformation of the arms when the object is gripped. A nano-tweezers device that applies a lock driving voltage determined in (1) to the electrostatic actuator. The nanotweezer device according to claim 1,
The control means applies an unlock driving voltage determined so that a Coulomb force generated by the electrostatic actuator is balanced with the elastic force after the pair of arms grips the object by the lock driving voltage. A nanotweezer device characterized by being applied to an actuator. The nanotweezer device according to claim 1 or 2,
The control means applies a grip driving voltage determined so that the pair of arms grips a symmetrical object with a predetermined gripping force when the target is gripped by the pair of open arms. Nanotweezers characterized by being applied to In the nano tweezers device according to any one of claims 1 to 3,
A lock switch for instructing application of the lock drive voltage, an unlock switch for instructing the unlock drive voltage, and a grip switch for instructing the grip drive voltage are arranged to be operated by an operator. A nanotweezer device comprising an operation panel. The nanotweezer device according to any one of claims 1 to 4,
The electrostatic actuator includes a comb-shaped fixed electrode and a comb-shaped movable electrode that meshes with the fixed electrode at a predetermined interval. The nanotweezer device according to claim 5,
An nano-tweezer device, wherein an insulating layer is provided on an opposing surface of at least one of the fixed electrode comb teeth and the movable electrode comb teeth. The electrostatic actuator such that after the pair of arms grips the object by an electrostatic actuator that is opened and closed by a Coulomb force, the Coulomb force exceeds an elastic force by the arm that deforms when the object is gripped. A method of gripping a micro sample, wherein a driving voltage is applied to the micro sample.

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