Title of Invention

"A SURFACE FORCE APPARATUS"

Abstract This invention relates to a surface force apparatus comprising mono-block assembly (1) two force sensors (9) and (10) machined to mono block, base plate is held to vibrations isolation table (2) having two linear variable differential transformer (LVDT) indicators (3,4), Laser PSD data acquisition system (5), stepper motor controller (6) and lock-in amplifiers (7) and wherein all these units are connected to central feed back unit (8) and miniature heater stage.
Full Text FIELD OF INVENTION
This invention relates to a Surface Force Apparatus (SFA) for directly measuring static and dynamic forces of the order of 1O9 to 10-3N acting between two surfaces over distances 1O6 to 10-10m, to determine mechanical properties, elastic and plastic deformations, colloidal forces, adhesive forces, capillary forces, viscoelastic properties, molecular wear resistance, boundary lubrication, etc.
PRIOR ART
Surface Force Apparatus (SFA) are advanced research instruments for measuring forces acting between two surfaces by using a combination of force and displacement sensors. SFA known in the art, generally consist of a force sensor, which is either a simple cantilever or a double cantilever. An indenting tip of spherical or cylindrical surface topology, is guided by a compliant mechanism. A stepper motor or a servo-motor with a 'translating mechanism is used as an actuator for coarse positioning of indenter while fine positioning is done with piezo-actuator. The movement of the indenter during coarse positioning is monitored and measured by a linear variable differential transformer (LVDT). The fine movement is given a by piezo-actuator and the resulting forces are monitored and measured by variety of instruments of nanometric and nanoNewtonic resolutions.
SFA was originally developed to measure static normal Vander Waal's forces between two surfaces immersed in a liquid or vacuum. Later development of the apparatus enabled the study of dynamic shear response of molecular thin liquid films sandwiched between two smooth surfaces. SFAs are now being developed for specific areas of research. The Surface Topography Microscope (STM) was developed which is capable of obtaining three-dimensional surface topography image of material, with atomic resolution. Subsequently, with modifications, number of Scanning Probe Microscopes (SPMs) have been developed for specific applications e.g. Atomic Force Microscopy (AFM), Friction Force Microscopy (FFM), Magnetic Force Microscopy (MFM) etc.
In recent years, a new generation of Surface Force Apparatus (SFAs) have been developed and modified to measure a wide range of physical and mechanical properties under different conditions. For example;- measurements of normal and frictional forces, wetting and capillary forces, adhesion, contact deformation, geometry of immobile layers, storage and loss modulus of viscous liquids as relevant in understanding of surfactants, boundary lubrication, surface chemistry of metals, metal

oxides, semiconductors, viscosity and other flow processes in thin film, monolayers properties, interactions of model bio-surfaces such as lipids,, bilayers etc. Through SFA experiments, static and dynamic properties of polymers have also been determined.
The displacement sensors use Multiple Beam Interferometry (MBI) Method or capacitive method or Laser-PSD method or Linear Variable Differential Transformer (LVDT). MBI method is used to measure the difference between two optically smooth transparent surfaces (usually mica) with highly reflecting silver coating on one side of each surface, which acts as mirror. The capacitor method is based upon the fact that when the gap between the capacitor plates varies, the capacitance (i.e. ratio of charge to voltage) changes. From this change, the distance or deflection can be me.asured based on relation of d = eA/C where A is area of plate, C is capacitance, d is distance/deflection and e is permittivity constant. In Laser-PSD method, a reflected laser beam is received by segmented photo-diode which converts it into current.The change in position of beam generates differential current corresponding to the position of the cantilever beam.
Linear Variable Differential Transformer (LVDT) is an electromagnetic device that produces an electrical voltage that is proportional to the displacement of a movable magnetic core. An LVDT has a coil winding assembly consisting of a primary coil and two secondary coils enclosed in a cylindrical case. A rod shaped magnetic core is provided within the coil winding assembly, which is free to move axially. Lock-in amplifiers are used to detect and measure the amplitude and phase of very small AC signals down to a few nanovoltsl which are buried in noise. They act as a narrow band pass filter to remove much of the unwanted noise while allowing the signal to be measured, to pass through it.
One of the Surface Force Apparatus known in the art is Mark II SFA i.e. second generation SFA designed by J.N Israelachvili wherein the force sensor is a variable stiffness double cantilever as against simple cantilever used in the earlier version of this apparatus. Multiple Beam Interoferometry (MBI) is used as displacement sensor to measure distance between two optically smooth transparent surfaces, usually mica. The distances between .the surfaces are adjusted by a micrometer for coarse positioning and by a piezo-translator for fine positioning.
One of the limitation of the above-mentioned SFA is that different parts introduce alignment errors and maximise thermal drift.

Another drawback of the above apparatus is that coarse positioning and fine positioning are not collinear which could introduce undesirable lever effects.
Still another drawback of the above apparatus is that use of the apparatus is restricted to only optically transparent and smooth surfaces.
Further draw back is that MBI method used in the apparatus is cumbersome and the resolution is limited to wavelength.
Another SFA known in the art is MarkJII SFA which has also been designed by J.N. Israelachvili which is similar to Mark II SFA with some additional features. It also uses double cantilever as Force sensor, MBI, a micrometer for rough positioning and piezo-translator for fine positioning. It has four controls instead of three controls provided in Markll SFA and has two chambers. The lower chamber is detachable and contains a variable stiffness spring while the upper chamber contains control system. Both the chambers are connected through teflon bellows. With further additional features like bimorph attachment with the force sensor spring and a semiconductor strain gauge attachment, SFA Mark III is capable of performing sliding, shear rate and frictional experiments.
However like Markll SFA, the above apparatus has also the drawback that coarse positioning by micrometer and fine positioning by piezo-translator are not collinear which could introduce undesirable lever effect.
Another drawback of the above mark III SFA is that different parts introduce alignment error and miximise thermal drift.
Still another drawback of the above mark III SFA is that even though double cantilever compliant mechanism ensures in-plane vertical deflection, it is difficult to eliminate second order rotational degrees of freedom and sideways deflection. Such distortions are not acceptable when the measurements are in molecular scale and in the testing of low stiffness samples.
Further drawback of the above mark III SFA is that it requires optically transparent and smooth surfaces which restricts the usage of different material surfaces, especially metals, at different atomic corrugation or roughness.
Yet further drawback of the above mark III SFA is that it uses MBI for displacement measurement which is cumbersome and the measurement by this method is limited by the wavelength.

Still another SFA known in the art is of French design wherein force sensor is a double cantilever spring and three capacitors are used as displacement sensors.
A drawback of the above-mentioned SFA is that like Mark III SFA, it is difficult to eliminate second order rotational degrees of freedom and sideways deflection.
Another drawback is that in the above design also, assembly parts introduce alignment errors and maximise thermal drift.
Still another drawback of the above French design apparatus is that alignment errors also arise due to different capacitor displacement sensors and the capacitance sensors are also prone to high thermal drift.
Another improved version of SFA known in the art has bimorph system attached to the double cantilever spring which can move the double cantilever laterally applying an appropriate AC/DC signal.
A drawback of the above SFA is that while this improved version registers higher sensitivities, it still has the drawbacks as outlined above for Mark-II and Mark-III SFA.
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Still another SFA known in the art is 'mechanical and surface probe nanaoprobe'(US patent 5,1 93,383) which has a tungsten wire probe which is driven by a sample, driven by piezoelectric actuator. Trie probe is suspended in air by being attached to two bent tungsten rod cantilever, each attached to a plate separately. The movement of the tip is measured at its rear point aligned with another tip. The movement is monitored by monitoring the tunneling current. This gives the force experienced by the cantilever. The voltage applied to the piezoelectric actuator is used to measure position and displacement within the instrument
A drawback of the above SFA is that there are two independent cantilevers, one holds while the other aligns the probe. The rotation of the probe is mechanically prevented to the extent of the identity between the bending geometry of the independent cantilevers and identity of their separate attachments to the plates. Any slight rotation of the. probe axis may introduce misalignment in generating tunneling current and hence the displacement measurement.
Another drawback of the above SFA is that there is no measurement of approach independent of the actuator.

Still another drawback of the above SFA is that there are too many joints between different components, all of which dissipate energy.
OBJECTS OF PRESENT INVENTION
The primary object of the present invention is to provide an integrated Surface Force Apparatus (SFA) which incorporates an integrated assembly of systems, has subsystems of novel/improved design, and which is capable of performing basic as well as research level measurements as existing SFAs.
Another object of the present invention is to provide an integrated Surface Force Apparatus (SFA) which minimises all undesirable errors by optimising structural design, displacement sensor and overall system design.
Still another object of the present invention is to use aluminium alloy instead of Cu-Be alloy used in most of SFAs known in the art to overcome the draw-back of special machining which is required for Cu-Be alloy due to its poisonous nature.
Yet another object of the present invention is to provide an integrated Surface Force Apparatus (SFA) which is user-friendly, compact and cost-effective.
Still another object of the present invention is to provide an integrated Surface Force Apparatus (SFA) which uses a force sensor of novel design referred herein as dual double cantilever system which eliminates the second order errors associated with double cantilevers used in the SFAs known the'art.
Yet another object of the present invention is to provide an integrated SFA which incorporates the dual double cantilever which has very high stiffness of the order of 100 to 1,00,000 N/m and therefore its performance is not affected by high temperature up to 300°C.
Another object of the present invention is to provide an integrated SFA wherein sample or probe are attached to one cantilever each of which due to the novelty of design, have nil rotation.
Yet another object of the present invention is to provide an integrated SFA wherein measurement of approach is independent of the actuator so that irrespective of the actuator movement, the probe and the sample movements are measured separately and independently by optical means.

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Further object of the present invention is to provide an integrated Surface Force Apparatus (SFA) which besides the capability for force measurements, is also able to determine molecular loss due to normal and extreme conditions (high temperature, pressure and chemical environment), molecular deformation, chemical and physical changes by in-situ observation using Raman or Infra-red spectroscopy.
Yet further object of the present invention is to provide an integrated Surface Force Apparatus of joint-less mono-block design which has a mono-block assembly with force sensors machined to it and has design which integrates various systems into one assembly by meeting the geometrical and positioning requirements of different individual systems, thereby eliminating alignment errors and sources of energy dissipation arising in the systems known in the due to different assembly parts .
Still further object of the present invention is to provide an integrated Surface Force Apparatus, which enables carrying out of measurements when the sample is heated.
Even further object of the present invention is to provide an integrated SFA which enables measurement involving probes, sample and substrates, which may be optically opaque or transparent.
Yet further object of the present invention is to provide an integrated SFA which incorporates a heater stage based on the principle different from known in the art, which is simple, cheap and removable and can be fixed mechanically with sample stage.
Even further object of the present invention is to provide an integrated SFA, which incorporates heater stage which enable to quantify the surface structure and chemistry of sample at high temperature range from room temperature to 300"C
Yet even further object of the present invention is to provide an integrated SFA wherein actuator is far away from the heated stage, so that the temperature near the actuator is maintained naturally in ambient condition and therefore high temperatures do not have any adverse effect on the characteristics of piezoelectric tube.

DESCRIPTION OF INVENTION
According to this invention relates to a surface force apparatus comprising mono-block assembly two force sensors and machined to mono block, base plate is held to vibrations isolation table having two linear variable differential transformer (LVDT) indicators, Laser PSD data acquisition system, stepper motor controller and lock-in amplifiers and wherein all these units are connected to central feed back unit and miniature heater stage.
This invention provides a surface force apparatus (SFA) to measure mechanical properties, viscoelastic properties, molecular wear resistance, etc. properties of liquids confined between two surfaces. The apparatus of the present

invention uses a pair offeree sensors of novel design referred to herein as 'dual double antilever system' as against simple cantilever system or double cantilever system used in SFAs known in the art. In case of simple cantilever used in some of the SFAs known in the art, there are rotations and sideways deflections at the free end, which cause first order errors in measurement which are especially undesirable inthe µN or nN ranges. In the case of double cantilever, first order errors may be eliminated by wise design modifications. Though the double cantilever ensures in-plane vertical deflection, it is difficult to eliminate second order degrees of freedom and sideways deflection. The second order errors can be avoided only by increasing the stiffness of the double cantilever which is at the cost of sensitivity and resolution of force sensor. These problems are overcome in the SFA of present invention, which incorporates a pair of novel force sensor namely 'dual double cantilever'. This dual double cantilever consists of two pairs of simple cantilevers, which are connected at the free end by rigid members which are further connected to each other by another rigid member (fig.3). The force sensor is made of AU4G 1(2024) Aluminum alloy heat treated to T4 condition, as against Cu-Be alloy used in most of the SFAs known in the art. The use of Cu-Be alloy in the known force sensors necessitates special machining procedure due to the poisonous nature of Beryllium. Unlike theSFAs known in the art, wherein there are two independent cantilevers one holding and other aligning the probe, in the SFA of the present invention, sample or the probe are attached to one cantilever, each of which due to the novelty of design has nil rotation. Another feature of the SFA of the present invention is that there measurement of approach independent of the actuator i.e. irrespective of the actuator movement, the probe and sample movements are measured separately and independently by optical means.
Another distinguishing feature of the SFA of present invention is anintegrated mono-block assembly which integrates all individual systems of the apparatus into one assembly thereby eliminating alignment errors, sources of energy dissipation and reduce thermal drift to negligible order of magnitude. These errors arise due to different assembly pans, and are generally experienced in the SFAs known in the art. The pair of new force sensors namely 'dual double cantilevers' discussed above, are machined to the mono-block frame. All the other individual systems namely stepper motor, coupling, micrometer, guider, guiding rods, translating rod, lasers, photodiodes, two linear variable Differential Transformers (LVDTs), and indenter are integrated into the mono-block which is designed to meet the geometrical and positioning requirements of .the individual systems.. The mono-block frame has been dimensionally optimised to be in the height: width: thickness ratio of 33:18:4. The SFA of the present invention uses a special miniature heating stage for speedy and uniform heating of the sample, upto the temperature of 290° C, with the help of RTD(Resister Temperature Detecter) circuit. The heating stage is simple, cheap and

can be mechanically fixed with sample stage. The heating stage is located far way from the actuator so that it has no effect on the characteristic of piezo-electric tube. The apparatus also incorporates either Laser Raman or IR spectroscopydetector for in-situ observation of deformity, physical or chemical changes in the liquids confined between the two surfaces.
The SFA of this invention uses a combination of two displacement sensors. One linear variable differential transformer (LVDT) of resolution lµm measures the
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displacement of guiding spring and other LVDT of resolution 1 µm measures the displacement of force sensor spring. The SFA of present invention also uses Laser-PSD sensor unit to measure the displacement of force sensor during dynamic experiment. Though laser and PSD (photo-sensitive diode) as individual components are known in the art, but software and hardware have been designed and developed to integrate them to the SFA. All the units are connected to a central feedback unit, which is controlled by a computer through data acquisition cards. Software and hardware have been designed and developed to integrate the individual systems with the computer controlled central feedback unit.
DESCRITION OF FIGURES
The present invention will now be described in detail w.r.t. accompanying drawings which are intended to illustrate an embodiment of the present invention and are not intended to imply any limitation on the scope of the present invention. The principles and features of the present invention, can be employed by those skilled in art, in various other embodiments. Such embodiments are intended to be within the scope of the present invention. In the accompanying drawings:-
Fig 1 Shows the full view of the overall assembly of integrated SFA
Fig 2(a) Shows the mono-block design with two force sensors (i.e. two dual
double cantilevers) machined to it, and having design to meet geometrical and positioning requirements to accommodate other systems.
Fig 2(b) Shows the front view of mono-block assembly
Fig 2 ( c) Shows the back view of mono-block assembly
Fig 3 Shows the design of dual double cantilever system
Fig 4 Shows the functioning of laser-PSD sensor
Fig 5 Shows the miniature heater stage

DESCRIPTION W.R.T. DRAWINGS
Referring to Fig 1, the Integrated SFA system comprises of a mono-block assembly (1) whose base plate is fixed to vibrations isolation table (2), with the help of screws (25,26,27, 28 (Fig 2b). The mono-block assembly (1) is connected to LVDT indicator (3), LVDT indicator (4), Laser-PSD data acquisition system (5), stepper motor controller (6) and lock-in amplifier (7). Stepper Motor controller (6) controls the operations of stepper motor (1 l)(Fig 2(b)). Lock-in amplifier detects and measures the amplitude and phase of very small signals to the extent of nanovolts received from both the Laser-PSD sensors. A heating unit (Fig5) is provided to heat the sample at different temperature with the help of RTD (resister Temperature Detector) circuit and the temperature of sample can be measured and controlled. All the units are connected to a central feedback unit (8), which is controlled by a computer through multi-channel data acquisition cards. The data acquisition card comprises of three major units namely 'input unit' to amplify the channel outputs and convert analog signal to digital signal by a 12 bit analog to digital converter, 'feedbackunit' selects sample rate data by a programmable 16-bit timer with crystal oscillator, and 'control unit' comprising of interrupt and DMA channel select switches to control and to receive input signals.
Referring to Fig 2 (a), the mono-block assembly has two dual double cantilevers (9, 10), which function as force sensors, which are machined to the mono-block,.frame and form an integral part of the mono-block assembly. The mono-block assembly has provisions for positioning all individual systems as shown in fig 2(b) and (c). The mono-block assembly thus is an integrated assembly and there are no assembly parts thereby eliminating alignment errors and sources of dissipating energy, experienced in the SFAs known in the art, due to different assembly parts. The dimensions of the mono-block frame have been optimised to have height:width:thickness ratio of 33:8:4. The entire mono-block is fabricated using EDM wire cutting process. The mono-block design includes all geometrical and positioning requirements of different individual system integrated to it, including LVDT and laser and PSD units.
Fig 2(b) shows the mono-block assembly fitted with all the individual systems. Stepper motor (11) serves as actuator for coarse positioning of indenter (24) or probe few µm close to the sample surface. The shaft of stepper motor (11) is connected to micrometer (13) through coupling (12). The micrometer (13) is connected to the guider (14) which is sliding on two guiding rods (15, 16) passing through guider (14). Both the ends of guiding rods (15, 16) are fixed to the mono-block frame and tightened by grip screws. One end of translating shaft (17) is connected to guider (14) and the other end is connected to guiding spring (47). The above arrangement converts the

rotary motion of the stepper motor (11) to translatory motion. The pitch of micrometer 'is 0.5mm. Normally one complete revolution of stepper motor (11) consist of 200 steps i.e. one full step is 1.8 degree. However a special software and control card has been developed for controlling stepper motor (11) through computer which enables half step option. In this half step mode, there are 400 steps per complete revolution and for each half step, and the translating shaft (17) moves 1.25µm i.e. pitch/total number of step = 0.5 mm/400 = 1.25µm. Stepper Motor Controller (6) (Fig 1) controls the operations of stepper motor (11). The mono-block assembly has two separate attachments (19, 20) for two lasers and two separate attachments (21, 22) for photodiodes. This design enables adjustment of 360° in-plane movements as well as out of plane movements. Also the distance between reflecting surface and laser or PSD can be adjusted easily. The magnification factor of reflecting surface displacement depends on angle of incidence of laser beam. Mono-block assembly has two Linear Variable Differential Transformer (LVDT) (18) and (23) (Fig 2 c) which have resolution of lµm or 0.1µm). One LVDT(18) measures the displacement 'd1' of the guiding spring (47) and the other LVDT(23) measures the displacement 'd2' of the force sensor spring(48). The difference between the displacement d| and d2 is measure of the penetration depth of indenter (24). During dynamic experiments, the displacement offeree sensors i.e. dual double cantilevers (9, 10) is measured by Laser-PSD sensor. The Strain gauges(30,31) shown in fig2(c), measure force independently in static experiment.
Fig 3 shows one of the force sensor namely the dual double cantilever system. The force sensor comprises of two pairs of single cantilevers (32,33,34,35) connected at the free ends by rigid members (36, 37). The two rigid members (36, 37) are further connected through another rigid member (38) on which sample is placed and load is applied. The configuration approximates to two double cantilevers connected in parallel. The stiffness of the dual double cantilever system is 16 times that of a single cantilever. This new force sensor is made out of rectangular block of aluminium alloy AU4G1 (2024) heat treated to T4 condition as against Cu-Be alloys used in most of SFAs known in the art which have disadvantage that these require special machining procedure due to poisonous nature of Beryllium. It is fabricated by using wire cut electro discharge machining.
In the simple cantilever based force sensor mechanism used in some of the SFAs known in the art, there are rotations and sideways deflection at the free end. These cause first order errors in measurement which are undesirable in the nN to mN ranges. The double cantilevers used in some of the SFAs known in the art, comprise of two simple cantilevers connected at the free end by a comparatively rigid L-shaped plate. The stiffness of such double cantilevers is 8 times that of simple cantilevers. In such

double cantilevers, first order errors are eliminated by wise design. The second order errors are avoided by stiffening the cantilever. However this is not a desirable move as it results in loss of sensitivity as well as the loss of resolution capability of the force sensor, particularly so when the material is soft. In the present invention, a pair oftwo dual double cantilevers as explained in the preceding paragraph, have been designed and incorporated in the SFA which eliminates the first order errors as well as second order errors without enhancing the stiffness of cantilever and therefore without jeopardising the sensitivity and resolution capability offeree sensor.
Referring to Fig 4, the photo-sensitive diode (PSD) consists of four quadrants (39,40,42,41) where-in each quadrant is separated by O.lmm non-conducting region. It is made of photosensitive material coated on non-conducting substrate. When light falls on it, it produces electric current the magnitude of which is proportional to the wave length and intensity of light. The current output of each quadrant is taken by connection wise, which is finally soldered on it. The relative voltages between vertical quadrants (39) and 42 or (40) and (41) gives vertical displacement offeree sensor and the relative voltages between diagonally opposite quadrants (39) and (41) or (40) and (42) give sideways displacement of force sensor.
Referring to Fig 5, the miniature heater stage comprises of a heating element (44), substrate (45) and highly thermal conducting material plate (43). The heating element (44) is fabricated by printed circuit laying technology and is made up of thin film of copper alloy. The substrate (45) is made up of electrical and thermal insulator. The thermal conducting material plate (43) is attached to heating element (44) by organic-ceramic compounds of low thermal expansion, electrical and thermal conducting material.
METHOD OF USE OF APPARATUS
The indenter (24) is moved in the y-direction (vertical direction) at a very slow rate ~ lµm/sec. When the indenter (24) touches the sample, the displacement sensor LVDT (23) shows the displacement. By careful control of the stepper motor (11), the initial surface contact can be established with an error of
independently measured by a strain gauge arrangement. After the indenter (24) reaches the desired indentation depth d, the indenter (24) is retracted at the same rate, which gives the unloading part of load-displacement curve. In the case of dynamic experiment, after the indenter (24) reaches the desired depth, sinusoidal displacement is applied through the stepper motor(ll), the Laser-PSD sensor measures the displacement of the force sensors (9, 10). The amplitude reduction of the sinusoidal displacement and the phase shift are measured by using the lock-in amplifier (7). The output from LVDTs, Laser-PSD strain gauges are converted into voltages through multi-channel data acquisition card which comprises of three major units namely input unit, feedback unit and control unit. The input unit amplifies the channel outputs by an amplifier and then the analog signals are converted into digital signal by a 12 bit analog to digital converter with offset and scale adjusting potentiometer and then is connected to PC BUS interface converter through a input port. Through the feedback loop of the feedback unit, sample rate data is selected by a programmable 16-bit timer with crystal oscillator and required number channels are scanned by channel scanner. The control unit consists of interrupt and DMA channel select switches to control and receive the input signals. In addition it hasDAS card address select switch and decoder with control logic.
It is to be understood that the apparatus of the present invention is susceptible to modifications, adaptations, changes by those skilled in the art without departing from the principal features of the embodiment described herein. Such changes, adaptations, modifications are intended to be within the scope of the present invention which is further set forth under the following claims:-








WE CLAIM;
1. A surface force apparatus comprising mono-block assembly (1)
two force sensors (9) and (10) machined to mono block, base plate
is held to vibrations isolation table (2) having two linear variable
differential transformer (LVDT) indicators (3,4), Laser PSD data
acquisition system (5), stepper motor controller (6) and lock-in
amplifiers (7) and wherein all these units are connected to central
feed back unit (8) and miniature heater stage.
2. A surface force apparatus as claimed in claim 1 wherein mono-
block assembly has two force sensors (9) and (10) machined to the
mono-block.
3. A surface force apparatus as claimed in claim 1 wherein force
sensors (9,10) are dual double cantilevers comprising two pairs of
single cantilevers (32, 33, 34, 35) connected at the free ends by
rigid members (36, 37) which are connected to each other by
another rigid member (38).
4. A surface force apparatus as claimed in claim 1 wherein mono-
block assembly integrates different individual systems stepper
motor (11), coupling (12), micrometer (13), guider (14), guiding
rods (15, 16), translating shaft (17), guiding spring (47), lasers (19,
20), photodiodes (21, 22) and two LVDTs (23, 18) and indentor
(24) into one assembly, meeting the geometrical and positioning
requirements of the different systems.
5. A surface force apparatus as claimed in claim 1 wherein sensors
are dual double cantilevers made of heat treated aluminum alloy.

b. A surface force apparatus as claimed in claim 1 wherein said miniature heater stage comprises of heating element (44) made up of copper alloy based on printed circuit technologies, highly thermal conducting material plate (43) and substrate (45) made of electrical thermal insulator wherein the said material place (43) is attached to heating element (44) by organic-ceramic compounds of low thermal expansion, electrical insulator and thermal conducting material.
7. A surface force apparatus as claimed in claim 1 wherein the said
miniature heater stage is capable of heating upto 290°C.
8. A surface force apparatus as substantially described and
illustrated herein.

Documents:

1062-del-2001-abstract.pdf

1062-del-2001-claims.pdf

1062-del-2001-correspondence-others.pdf

1062-del-2001-correspondence-po.pdf

1062-del-2001-description (complete).pdf

1062-del-2001-drawings.pdf

1062-del-2001-form-1.pdf

1062-del-2001-form-18.pdf

1062-del-2001-form-2.pdf

1062-del-2001-form-26.pdf

1062-del-2001-form-3.pdf


Patent Number 244575
Indian Patent Application Number 1062/DEL/2001
PG Journal Number 51/2010
Publication Date 17-Dec-2010
Grant Date 10-Dec-2010
Date of Filing 16-Oct-2001
Name of Patentee THE ADDITIONAL DIRECTOR (IPR)
Applicant Address B-341, SENA, BHAWAN, DHQ P.O. NEW DELHI-110011, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 SANJAY KUMAR BISWAS DEPARTMENT OF MECHANICAL ENGINEERING, INDIAN INSTITUTE OF SCIENCE, BANGALORE-560 012, INDIA.
2 DEVAPRAKASAM DEPARTMENT OF MECHANICAL ENGINEERING, INDIAN INSTITUTE OF SCIENCE, BANGALORE-560 012, INDIA.
PCT International Classification Number G01N 37/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA