WO2007036613A1

WO2007036613A1 - System and method for handling microscopic objects, and computer program

Info

Publication number: WO2007036613A1
Application number: PCT/FI2006/050419
Authority: WO
Inventors: Marko Pudas; Kari Laasonen; Juha Röning
Original assignee: Oulun Yliopisto
Priority date: 2005-09-30
Filing date: 2006-09-29
Publication date: 2007-04-05
Also published as: FI20055525A0; FI20055525A

Abstract

The invention relates to a system and a method for handling microscopic objects and to a computer program product. The system comprises: at least two contact heads arranged to establish a contact between a microscopic object and the contact heads, the dimensions of the contact portions of the contact heads being in the order of the microscopic object; a fine drive mechanism arranged to move at least one contact head at a microscopic accuracy with respect to at least one other contact head on the basis of a control signal fed into the fine drive system; and response means for detecting a contact response generated in the establishment of the contact between the microscopic object and the contact heads and for generating a response signal characterizing the contact response.

Description

SYSTEM AND METHOD FOR HANDLING MICROSCOPIC OBJECTS, AND COMPUTER PROGRAM

FIELD

[0001] The invention relates to a system and a method for handling microscopic objects and to a computer program.

BACKGROUND

[0002] Along with the advance of science and technology, the need for examining microscopic objects, such as cells, fibres and microparticles, has increased considerably. In that case, it is also necessary to physically handle, for example to touch, measure, probe and move, single microscopic objects.

[0003] Freehand handling of microscopic objects is not feasible, for which reason it is necessary to recourse to auxiliary instruments, such as mechanical screws, which the user operates on the basis of visual observations made from the object to be handled through a microscope, for example. [0004] A problem associated with visual observation is its low observation dynamics. It is thus difficult to control the forces used in handling through auxiliary instruments, which may have a harmful effect on the microscopic object. Consequently, it is useful to consider various techniques for handling microscopic objects.

BRIEF DESCRIPTION

[0005] An object of the invention is to provide a system, a computer program and a method so as to allow dynamic handling of a microscopic object.

[0006] According to a first aspect of the invention, there is provided a system for handling microscopic objects, the system comprising: at least two contact heads arranged to establish a contact between a microscopic object and the contact heads, the dimensions of the contact portions of the contact heads being in the order of the microscopic object; a fine drive mechanism arranged to move at least one contact head at a microscopic accuracy with re- spect to at least one other contact head on the basis of a control signal fed into the fine drive system; and response means for detecting a contact response generated in the establishment of the contact between the microscopic object and the contact heads and for generating a response signal characterizing the contact response. [0007] According to a second aspect of the invention, there is provided a computer program comprising encoded instructions for executing a computer process in a digital processor of a computer, the computer process controlling handling of microscopic objects in a system, the system comprising: at least two contact heads arranged to establish a contact between a microscopic object and the contact heads, the dimensions of the contact heads being in the order of the microscopic object; a fine drive mechanism arranged to move at least one contact head at a microscopic drive accuracy with respect to at least one other contact head on the basis of a control signal fed into the fine drive system; and response means for detecting a contact response generated in the establishment of the contact between the microscopic object and the contact heads and for generating a response signal characterizing the contact response, the computer program further comprising encoded instructions for processing the control signal and for processing the response signal. [0008] According to a third aspect of the invention, there is provided a method of handling microscopic objects in a system, the system comprising: at least two contact heads arranged to establish a contact between a microscopic object and the contact heads, the dimensions of the contact heads being in the order of the microscopic object; a fine drive mechanism arranged to move at least one contact head at a microscopic drive accuracy with respect to at least one other contact head on the basis of a control signal fed into the fine drive system; and response means for detecting a contact response generated in the establishment of the contact between the microscopic object and the contact head and for generating a response signal characterizing the contact response, the method comprising: processing the control signal; and processing the response signal.

[0009] Preferred embodiments of the invention are disclosed in the dependent claims.

[0010] The invention is based on detecting a contact response gen- erated in a contact between a microscopic object and the contact heads of a system and producing a response signal characterizing the contact response.

[0011] The method and system according to the invention provide several advantages. An advantage of the invention is that it enables a contact between the microscopic object and the contact heads on the basis of the con- tact response of control, which allows selection of the force to be directed at the microscopic object in a manner suitable for the situation. LIST OF FIGURES

[0012] The invention will now be described in greater detail by means of preferred embodiments, with reference to the accompanying drawings, in which Figure 1 illustrates a first example of the structure of a system,

Figure 2 illustrates a second example of the structure of a system, Figure 3 illustrates a third example of the structure of a system, and Figure 4 illustrates an example of the structure of a control system.

DESCRIPTION OF EMBODIMENTS [0013] Referring to the example of Figure 1 , a system 100 comprises at least two contact heads 102A, 102B, of which at least one contact head 102A is connected to a fine drive mechanism 104A for moving the contact head 102A with respect to another contact head 102B. Moving enables establishment of a contact between the contact heads 102A, 102B and a mi- croscopic object 128, and hence handling of the microscopic object 128 by means of the contact heads 102A, 102B.

[0014] The contact heads 102A, 102B have been dimensioned and possibly shaped so as to allow the contact heads 102A, 102B to establish a contact with the microscopic object 128. [0015] The contact head 102A, 102B is typically made of a material which is in the solid state when the system 100 is used. The solid state may be generated by means of temperature, an electric field and/or a magnetic field, for example.

[0016] The contact heads 102A, 102B may be functional parts, in- eluding micro-tools, such as a saw, oscillator, knife and/or a tubular structure for transporting chemicals or sample particles.

[0017] The contact head 102A, 102B typically comprises a contact portion 134A, 134B, whose dimensions are in the order of the dimensions of the microscopic object 128. The contact portion 134A, 134B is the part of the contact head 102A, 102B that forms a contact with the microscopic object. The contact portion 134A, 134B is, for example, a pointed blade-like structure, which may partly penetrate into the microscopic object 128 to be handled. In an embodiment, the contact portion 134A, 134B may be shaped into a cup-like structure corresponding to the shape of the microscopic object 128. [0018] The length of the contact head 102A, 102B may be in a range of 50 μm to 10 mm without limiting the presented solution to this length range.

[0019] The microscopic object 128 is typically an object invisible to the naked eye and having at least one dimension of a microscopic order. The microscopic order is, for example, less than one tenth of a millimetre. Thus the dimension of the blade of the contact head's 102A, 102B contact portion 134A is typically in the order of less than one tenth of a millimetre, which enables handling the microscopic object 128. In an embodiment, the sharpness of the contact portion 134A, 134B is of an atomic order, enabling a tunnelling effect between the contact heads 102A, 102B, for example.

[0020] In an embodiment, the contact heads 102A, 102B are arranged to direct energy, such as radiation or a physical force stimulus, at the microscopic object 128. [0021] In an embodiment, the dimension of the contact portion's

134A, 134B blade is less than 10 μm.

[0022] In an embodiment, the dimension of the contact portion's 134A, 134B blade is less than 1 μm.

[0023] In an embodiment, the dimension of the contact portion's 134A, 134B blade is less than 100 nm.

[0024] In an embodiment, the dimension of the contact portion's 134A, 134B blade is less than 10 nm.

[0025] In an embodiment, the dimension of the contact portion's 134A, 134B blade is less than 1 nm. [0026] The microscopic object 128 is, for example, a biological unit, such as a cell, cell cluster, paper fibre or particle. The solution described is not limited to the above-mentioned microscopic objects but the microscopic object may be any small object. The presented solution enables handling microscopic objects, such as grabbing, moving, analyzing, pressing, measuring and/or stretching them.

[0027] The microscopic object 128 may be in a liquid, gas or vacuum.

[0028] The fine drive mechanism 104A is, for example, a mechanical actuator based on a solenoid or piezo and having at least one contact head 102A attached thereto. In an embodiment, the fine drive mechanism 104A may be arranged so that the range of movement of the contact head 102A is less than 10 μm, whereby the drive accuracy of the fine drive mechanism 104A may be better than 1 A. The range of movement is affected by the length of the fine drive mechanism, such as the dynamic range of the piezo actuator, and the length of the contact head 102A. The presented solution is not, however, limited to the 10-μm range of movement but the range or movement may also be shorter or longer.

[0029] The fine drive mechanism 104A may move the contact head 102A in a three-dimensional, two-dimensional or one-dimensional space.

[0030] The fine drive mechanism 104A is typically controllable by an electric control signal 106A. The control signal 106A is, for example, control power from the piezo actuator or solenoid.

[0031] The contact between the contact heads 102A, 102B and the microscopic object 128 produces a contact response, which may be detected by response means 108. The response means 108 generate a response signal 110 characterizing the contact response. The response means 108 may be an electrode provided on the surface of the contact head 102A, 102B or a sensor which examines a sample.

[0032] In an embodiment, the contact response is an imaging response, in which case the response means 108 is, for example, an imaging means, such as a camera or spectrometer. In an embodiment, the imaging means may be digital. In this case, the response means 108 may comprise image processing algorithms, which process changes caused by the contact in the microscopic object 128 and/or contact heads 102A, 102B, for example. The response means 108 may also include radiation means for directing elec- tromagnetic radiation or particle radiation at the contact area formed by the contact heads 102A, 102B and the microscopic object 128. The radiation is detected in the imaging means.

[0033] Referring further to Figure 1 , in an embodiment the system comprises a rough drive mechanism 112 for changing the position of the con- tact heads 102A, 102B with respect to the microscopic object 128. The travel of the rough drive mechanism 112 is typically longer than that of the fine drive mechanism 104A, and the drive accuracy may be lower than that of the fine drive mechanism 104A. The travel of the rough drive mechanism may be tens of centimetres and the drive accuracy in an order of 0.1 μm. The rough drive mechanism 112 may be controlled by an electric signal 126 or mechanically by the user. The rough drive mechanism 112 may move in a three-dimensional, two-dimensional or one-dimensional space. The rough drive mechanism 112 may comprise one or more components, such as an x-actuator with two different accuracies, for optimising the travel and resolution.

[0034] The rough drive mechanism 112 may be implemented by means of microscrews, piezos, servos and/or solenoids, for instance.

[0035] In an embodiment, the rough drive mechanism 112 moves the fine drive mechanism 104A and contact heads 102A, 102B. In that case, a sample including the microscopic object 128 may be on a fixed substrate.

[0036] In an embodiment, the rough control mechanism 112 moves a sample including the microscopic object 128. In that case, the fine drive mechanism 104A and contact heads 102A, 102B may be fixed to the system's 100 frame.

[0037] Referring further to Figure 1 , the system 100 may also comprise a control unit 114 and user interface 116. [0038] The control unit 114 processes a control signal 106A of the fine drive mechanism 104A. The processing may comprise generation of the control signal 106A on the basis of a primary control signal 122 received from the user interface 116. The generation of the control signal 106A may comprise conversion of the control signal 106A from its digital format into an analog one as well as conversion of the current, voltage and/or frequency from the analog format into a format suitable for the fine drive mechanism 104A. The control unit 114 may further perform control functions of the response means 108.

[0039] Furthermore, the control unit 114 receives a response signal 110 and processes it. The processing of the response signal 110 may comprise filtering of the response signal 110 and its conversion from a digital format into an analog one. In an embodiment, the processing of the response signal 110 comprises separation of the direction components of the response signal 110 from one another and feeding of the direction components into the user interface 116.

[0040] The control unit 114 may further generate a control signal 126 for the rough drive mechanism 112.

[0041] In an embodiment, the control unit 114 is configured to generate the control signal 106A on the basis of the response signal 110, in which case the handling of the microscopic object may automatically take the contact response detected by the response means 108 into account. This functionality may be employed in the grabbing of the microscopic object 128, for instance, in which case the control signal 106A may include a command to reduce the contact force directed at the microscopic object 128 when the contact response indicates a sufficiently strong contact. In this case, the movement of the contact heads 102A, 102B can be stopped automatically after the contact response has reached a certain limit value.

[0042] The user interface 116 typically comprises one or more controllers (D-CNTL) 118 and stimulus means (R-MON) 120. The controller 118 is typically a device by means of which the user may control the control signal 106A on the basis of the physical control he/she has produced. In that case, the controller 118 generates a primary control signal 122, which is converted into a control signal 106A in the control unit 114.

[0043] The controller 118 is, for example, a 3-dimensional joystick, a mouse, a controller levitating on magnets, a pedal, a data glove or an audio controller. In an embodiment, the kinetic logic of the contact heads 102A, 102B, such as directions, is analogous with the kinetic logic directed at the controller 118. In that case, the kinetic logic of the contact heads 102A, 102B is similar to the kinetic logic of the joystick or 3-dimensional controller.

[0044] The stimulus means 120 comprises a device for providing a physical stimulus for the user on the basis of a secondary response signal 124. The secondary response signal 124 is a signal generated from the response signal 110 by the control unit 114 and contains contact response information in a form decodable by the stimulus means 120. In the stimulus means 120, the contact response realizes into a physical stimulus observable by the user, such as a sound or tactile response, for example force and/or vibration. The stimulus means 120 comprise an audio device, a visual device, a mechanical device producing compression or motion and/or a device generating vibration, for instance.

[0045] In an embodiment, the stimulus means 120 are integrated into the controller 118, and the stimulus means 120 and controller 118 are configured to use common physical logic. In that case, a component producing the response is integrated into the joystick, such as a servo or solenoid, which directs a stimulus at the user in accordance with the kinetic logic used in controlling the joystick. One example is a situation where the contact heads 102A, 102B press the microscopic object 128 or the surface. In that case, the stimulus means 120 may produce a force opposite to the control force as an indica- tion of an increase in the contact force due to a stronger compression force. In that case, the compression dynamics is transmitted to the user's body and the user may, on the basis of the contact response, control the force needed in handling the microscopic object 128. [0046] Referring to the example of Figure 2, we will examine a system 200 comprising contact head specific fine drive mechanisms 104A, 104B, of which fine drive mechanism 104A moves contact head 102A and fine drive mechanism 104B contact head 102B. In the presented example, the fine drive mechanisms 104A, 104B are attached to the system's fixed structure, and the rough drive mechanism 112 moves the sample included in the microscopic object 128. The fine drive mechanisms 104A, 104B may be controlled by fine drive mechanism specific control signals 106A, 106B.

[0047] In the example illustrated in Figure 2, at least one contact head 102A, 102B has been manufactured of a conductive material, such as metal, surface-conductive polymer, graphite and/or carbon nanotube. The control unit 114 may comprise a current controller (AMP CNTL) 202 for supplying electric current 204A, 204B to the contact head 102A, 102B. In that case, the electric current 204A, 204B may also function as a response signal. The contact between the contact head 102A, 102B and the microscopic object may produce a current response that affects the passing of the electric current 204A, 204B in the conductive contact head 102A, 102B. The current response may be based on at least two mechanisms. In one mechanism, the microscopic object 128 affects the current passing between the contact heads 102A, 102B, in which case the current controller 202 defines the electric current 204A, 204B that passes through the contact heads 102A, 102B. An increased current response may indicate, for example, that the contact between the contact heads 102A, 102B and the microscopic object 128 has strengthened, in which case a stimulus corresponding to the current response may be directed at the user through the stimulus means 120. In that case, the user may control the contact heads 102A, 102B in a desired direction through the controller 118. [0048] In a preferred embodiment, the current response is caused by tunnelling of charges between the contact heads 102A, 102B or between the contract heads 102A, 102B and the microscopic object 128.

[0049] In an embodiment, the electric current 204A, 204B passes through the conductive contact head 102A, 102B and the microscopic object 128 to a sample substrate 208. In that case, the sample substrate 208 may be connected to the current controller 202, which receives the response signal. In an embodiment, the sample is connected directly to the current controller 202. [0050] The current controller 202 typically comprises a current source and a current measuring circuit. The voltage of the current source may be between 1 mV and 100 V and the current between 1 pA and 100 mA without limiting the presented solution to these figures. The current measuring circuit determines the magnitude of the current that has passed through the contact head 102A, 102B and generates a secondary response signal 124 characterizing the magnitude of the current. [0051] Referring to the example illustrated in Figure 3, the system

300 may be implemented using a common fine drive mechanism 308 for more than one contact head 102A, 102B. The fine drive mechanism 308 may be a piezo actuator, servo or solenoid, for instance.

[0052] In an embodiment, the system 300 comprises force response means 302A, 302B, 310 for determining the contact force between the microscopic object 128 and the microscopic object 128 and for generating a response signal 306A, 306B characterizing the contact force.

[0053] In an embodiment, the force response means 302A, 302B, 310 are implemented by determining the numeric value of the electric control signal 106A. In the case of a piezo actuator or solenoid, for example, the control current required by the position of the contact heads 102A, 102B is determined. In that case, the force required to handle the microscopic object 128 may be determined from the numeric value of the control signal 106A. The numeric value of the control signal 106A may be converted into a secondary response signal 124 and fed into the stimulus means 120. In this case, blocks 302A, 302B are not necessary, and a force determination unit 310 may be integrated into the control system of the fine drive mechanism.

[0054] In an embodiment, the force response means comprise at least one bend determiner arranged in connection with the contact head 102A, 102B for determining the bend of the contact head 102A, 102B. In this case, blocks 302A, 302B define primary bend.

[0055] In an embodiment, the bend determiner is based on a stretch sensor 302A, 302B connected to the contact head 102A, 102B, the sensor detecting deformation of the contact head 102A, 102B as the contact between the contact heads 102A, 102B and the microscopic object 128 strengthens. The signal 312A, 312B of the stretch sensor is supplied to the force determina- tion unit 310, where the signal 312A, 312B is converted into a variable characterizing the force when the geometry and scaling factors of the stretch measurement are known. The value of the variable characterizing force may be included in the secondary response signal 124, which is fed into the stimulus means 120 of the user interface 116.

[0056] In an embodiment, the bend determiner is based on optical measurement where an optical measuring device 302A, 302B directs optical radiation 304A, 304B, such as laser radiation, at the contact head 102A, 102B. The contact head emits reflected radiation 306A, 306B, which is detected in the optical measuring device 302A, 302B. The reflected radiation 306A, 306B may be analysed interferometrically, for instance, in which case the bend of the contact head 102A, 102B may be determined at an accuracy in the order of the wavelength of the radiation 304A, 304B. The radiation may be generated and detected by photoelectric components, such as diodes. [0057] The optical measurement may also be based on NSOM

(Near-field Scanning Optical Microscopy) technology.

[0058] The optical measurement device 302A, 302B generates a response signal 312A, 312B on the basis of optical determination it has carried out and feeds the response signal 312A, 312B into the force determination unit 310. The force determination unit 310 may, for example, convert the bend information included in the response signal 312A, 312B into information which characterizes the compression force and is fed into the stimulus means 120 in the secondary response signal 124.

[0059] The optical measurement may also be based on the use of optically conductive material in the manufacture of the contact head 102A, 102B, in which case the contact head 102A, 102B functions like an optical fibre. In that case, the contact head 102A, 102B is supplied with radiation whose phase is dependent on the bend of the contact head 102A, 102B. The phase may be detected by a detector arranged in the vicinity of the contact head 102A, 102B or in the control unit 114. In an embodiment, optical radiation is directed at the microscopic object 128 by one measuring head, and the radiation emitted from the microscopic object is fed into the response means by the other measuring head 102B.

[0060] Referring to Figure 1 , the force response means can also be implemented by installing a response means 108 between the fine drive mechanism 104A and the rough drive mechanism 112, the response means 108 measuring the mechanical stress directed at the fine drive mechanism 104A during the contact. In an embodiment, the response means 108 is attached between the system's frame and the rough drive mechanism 1 12, the response means 108 measuring the stress directed at the rough drive mecha- nism 1 12 and originating from the forces directed at the contact heads 102A, 102B.

[0061] Referring to Figures 1 , 2 and 3, the different embodiments of the system 100, 200, 300 may be implemented by various combinations of the fine drive mechanism 104A, 104B, 308, rough drive mechanism 1 12 and re- sponse means 108, 202, 302A, 302B, 310. The rough drive mechanism 1 12 may move the contact heads 102A, 102B or the sample. The system 100, 200, 300 may comprise several contact head specific fine drive mechanisms 104A, 104B or a fine drive mechanism 308 common to the contact heads 102A, 102B. The response means 108, 202, 302A, 302B, 310 may be combined with any fine drive mechanism 104A, 104B, 308 and/or rough drive mechanism 1 12.

[0062] Referring to the example of Figure 4, the control unit 114 comprises a digital processor (DP) 408 for executing a computer process defined by encoded instructions and a memory unit (MEM) 406 for storing the encoded instructions. The digital processor 408 and memory unit 406 form a computer for the control unit 114. The digital processor 408 and memory unit 406 may be integrated into the same microcircuit.

[0063] The control unit 1 14 further comprises drive electronics (DE) 402, response electronics (RE) 404 and a connection interface (Cl) 410 con- nected to the digital processor 408.

[0064] The digital processor 408 processes a digital control signal 412, which controls the fine drive mechanic 104A, 104B and is fed into drive electronics 402. In the drive electronics 402, the digital control signal 412 is converted into a control signal 422. The digital control signal 412 typically in- eludes information on physical properties of the control signal 422, such as voltage, current, waveform and/or frequency.

[0065] The control signal 126 for the rough drive mechanism 112 may be generated in the drive electronics 402 or in separate drive electronics for the rough drive mechanism. [0066] The drive electronics 402 may comprise a digital-to-analog converter, voltage converter, current limiter, optoelectric converter and/or fre- quency converter. The presented solution is not, however, limited to the electronic elements listed above.

[0067] The response electronics 404 receives a response signal

416 and subjects it to signal processing, such as amplification, analog filtering, analog-to-digital conversion and/or digital filtering. The response electronics

404 feeds a digital response signal 414 obtained from signal processing into the digital processor 408.

[0068] The digital processor 408 processes the digital response signal 414 on the basis of encoded instructions stored in the memory unit 406 and feeds a secondary digital response signal 420 into the connection interface 410.

[0069] In an embodiment, the encoded instructions include an instruction for generating the digital control signal 412 on the basis of the digital response signal 414. [0070] The connection interface 410 functions as an interface between the digital processor 408 and the user interface 116. The connection interface 410 may comprise a communication port for connecting the control unit 114 to the user interface 116. The primary control signal 122 is fed into the control unit 114 through this communication port as well as the secondary re- sponse signal 124 from the control unit 114 into the user interface 116.

[0071] One of the functions of the computer process executed by the control unit 112 is to perform scaling between macroscopic functions related to the connection interface 410 and microscopic functions related to the fine drive mechanism 104A, 104B and response means 108, 302A, 302B and to carry out the necessary coordinate transformations.

[0072] The connection interface 410 may also comprise electronics for converting the primary control signal 122 into a primary digital signal 418. The connection interface 410 may further comprise electronics for converting the secondary digital response signal 420 into a secondary response signal 124. The primary control signal 122 and/or secondary control signal 124 may also be digital signals.

[0073] In an embodiment, the digital processor 408 processes the digital control signal 412 on the basis of a primary control signal 122 received from the system's 100, 200, 300 controller 118 in accordance with the encoded instructions. The system 100 controller 118 receives the physical control generated by the user. [0074] In an embodiment, the digital processor 408 converts, in accordance with the encoded instructions, the response signal into a format that corresponds to a desired physical stimulus, which is directed at the user by the system's stimulus means 120. [0075] In an embodiment, the digital processor 408 processes the digital response signal and digital control signal according to encoded instructions on the basis of a common physical logic.

[0076] In an embodiment, the digital processor 408 and memory unit 406 form an adaptive neural network, which follows a behaviour pattern stored as encoded instructions in the memory unit 406. The neural network may also be implemented by FPGA (Filed Programmable Gate Array) technology.

[0077] The encoded instructions may be embodied in the computer program product. The encoded instructions may be decodable by the computer of the control unit 1 14 and embodied in a distribution medium decodable by a computer. The distribution medium may be, for example, an electric, magnetic or optical distribution medium. The distribution medium may be a physical distribution medium, such as a memory unit, optical disc or telecommunications signal. [0078] According to an aspect of the invention, there is provided a method of handling a microscopic object. The method comprises processing a control signal 422 and a response signal 416 in a control unit 114 according to Figure 4, for instance.

[0079] In an embodiment, the control signal 422 is processed on the basis of the response signal 416.

[0080] In an embodiment, the control signal 422 is processed on the basis of a primary control signal 122 received from the system's controller.

[0081] The system described above enables responsive computer- controlled microtweezer functionality, which allows dynamic handling of micro- scopic objects.

[0082] Even though the invention was described above with reference to the example according to the accompanying drawings, it is clear that the invention is not limited thereto, but it may be varied in several ways within the scope of the attached claims.

Claims

1. A system for handling microscopic objects, characterized in that the system comprises: at least two contact heads (102A, 102B) arranged to establish a contact between a microscopic object and the contact heads (102A, 102B), the dimensions of the contact portions of the contact heads (102A, 102B) being in the order of the microscopic object; a fine drive mechanism (104A, 104B) arranged to move at least one contact head (102A) at a microscopic accuracy with respect to at least one other contact head (102B) on the basis of a control signal (106A, 106B) fed into the fine drive system (104A, 104B); and response means (108, 202, 302A, 302B) for detecting a contact response generated in the establishment of the contact between the microscopic object and the contact heads and for generating a response signal (110, 204A, 204B, 206, 312A, 312B) characterizing the contact response.

2. A system according to claim 1 , characterized in that the response means (108, 202, 302A, 302B) comprise imaging response means (108) for determining an imaging response produced by the contact between the microscopic object and the contact heads (102A, 102B) and for generating a response signal (204A, 204B, 206) characterizing the imaging response.

3. A system according to claim 1 , characterized in that at least one contact head (102A, 102B) is configured to conduct electric current; and the system comprises current response means (202) for determining a current response produced by the contact between the microscopic ob- ject and the contact heads (102A, 102B) in the electric current passing through the at least one contact head (102A, 102B) and for generating at least one response signal (204A, 204B, 206) characterizing the current response.

4. A system according to claim 1 , characterized in that the response means comprise force response means (302A, 302B, 310) for deter- mining contact force between the microscopic object and the contact heads (102A, 102B) and for generating a response signal characterizing the contact force.

5. A system according to claim 4, characterized in that the force response means (302A, 302B, 310) comprise at least one bend determiner arranged in connection with at least one contact head (102A, 102B) for determining bend of the contact head (102A, 102B).

6. A system according to claim 1 , characterized in that at least one contact head (102A, 102B) is made of optical conductive material; and the system comprises means for determining the contact response on the basis of a phase difference of optical radiation generated in at least one contact head (102A, 102B).

7. A system according to claim 1 , characterized in that the fine drive mechanism (104A, 104B) comprises at least one piezo-electric actuator for moving at least one contact head (102A, 102B) with respect to at least one other contact head (102A, 102B).

8. A system according to claim 1 , characterized in that the system further comprises a rough drive mechanism (1 12) for changing the location between the at least two contact heads (102A, 102B) and the microscopic ob- ject, the travel of the rough drive mechanism (112) being larger than the drive accuracy of the fine drive mechanism (104A, 104B).

9. A system according to claim 1 , characterized in that the system further comprises a control system (1 14) configured to receive a response signal (110, 204A, 204B, 206, 312A, 312B) and generate a control signal (106A, 106B) on the basis of the response signal (1 10, 204A, 204B, 206, 312A, 312B).

10. A system according to claim 1 , characterized in that the system further comprises a controller (1 18) configured to control the control signal (106A, 106B) on the basis of physical control produced by the user.

1 1. A system according to claim 1 , characterized in that the system further comprises stimulus means (120) for producing a physical stimulus for the user on the basis of the response signal (1 10, 204A, 204B, 206, 312A, 312B).

12. A system according to claims 10 and 1 1 , characterized in that the stimulus means (120) are integrated into the controller (1 18), and that the stimulus means (120) and the controller (1 18) are configured to use a common physical logic.

13. A computer program comprising encoded instructions for executing a computer process in a digital processor of a computer, the com- puter process controlling handling of microscopic objects in a system, the system comprising: at least two contact heads arranged to establish a contact between a microscopic object and the contact heads, the dimensions of the contact heads being in the order of the microscopic object; a fine drive mechanism arranged to move at least one contact head at a microscopic drive accuracy with respect to at least one other contact head on the basis of a control signal fed into the fine drive system; and response means for detecting a contact response generated in the establishment of the contact between the microscopic object and the contact heads and for generating a response signal characterizing the contact re- sponse, the computer program further comprising encoded instructions for processing the control signal and for processing the response signal.

14. A computer program according to claim 13, characterized in that the computer program further comprises encoded instructions for generating a control signal on the basis of the response signal.

15. A computer program according to claim 13, characterized in that the computer program further comprises encoded instructions for processing the control signal on the basis of a primary control signal received from the system controller, the system controller being arranged to receive physical control produced by the user.

16. A computer program according to claim 13, characterized in that the computer program further comprises encoded instructions for converting the response signal into a format corresponding to a desired physical stimulus, which is directed at the user by stimulus means of the system.

17. A computer program according to claims 15 and 16, charac- terized in that the computer program comprises encoded instructions for processing the control signal and response signal using a common physical logic.

18. A computer program product according to claim 13, characterized in that the computer program product comprises the computer pro- gram.

19. A method of handling microscopic objects in a system, cha racterized in that the system comprises: at least two contact heads arranged to establish a contact between a microscopic object and the contact heads, the dimensions of the contact heads being in the order of the microscopic object; a fine drive mechanism arranged to move at least one contact head at a microscopic drive accuracy with respect to at least one other contact head on the basis of a control signal fed into the fine drive system; and response means for detecting a contact response generated in the establishment of the contact between the microscopic object and the contact head and for generating a response signal characterizing the contact response, the method comprising: processing the control signal; and processing the response signal.

20. A method according to claim 19, characterized by processing the control signal on the basis of the response signal.

21. A method according to claim 19, characterized by processing the control signal on the basis of a primary control signal received from the system controller.