Claims:WE CLAIM:
1. A touchpad device comprising
a pair of touchpad substrates, each touchpad substrate having conductive material coating on one side enabling electrical conductivity and dielectric material coating on opposite side for protective coating for hosting touch locations on said touchpad substrate;
said pair of touchpad substrates disposed one above the other such that the conductive material coated surface of one touchpad substrate faces towards of the conductive material coated surface of another touchpad substrate;
said conductive material coated surfaces of the touchpad substrates maintained in contactless disposition with at least one switching point of an air gap in between the conductive coated surfaces for touch and press based contact there between for the conducting coating of said touchpad substrates in said region for electrical conductivity and switching on connection and non-conducting and switching off disconnection on release of said press touch and press action.

2. A touchpad device as claimed in claim 1, wherein the pair of touchpad substrates comprises a dielectric spacer sandwiched within the conductive material coated surfaces to maintain the air gap;
said dielectric spacer is decorated with multiple holes to host the air gaps corresponding to the switching points and operate as targeted touch locations of the touchpad device.

3. A touchpad device as claimed in anyone of claim 1 or 2, wherein the conductive material coated side of the touchpad substrates include metal connectors to electronically connect said conductive material coated side of the touchpad substrates with an external controlling module and supply voltage associated with the touchpad device to facilitate controlling of a cooperative electronic application in accordance with touching of different location of the dielectric material coated side of the touchpad substrate.

4. A touchpad device as claimed in anyone of claims 1 to 3, wherein the controlling module is enabled to receive current flow from the supply voltage specific to the touch location, when said touch location in the outer dielectric coated surface of the polymer substrate is touched and the polymer substrate bends at the touch location where the hole is decorated in the dielectric spacer and the conductive coating on the inner side of the touched polymer substrate came in contact with the conductive coating on the inner side of the untouched polymer substrate as the air gap between the graphite coated inner surfaces is vanished.

5. A touchpad device as claimed in anyone of claims 1 to 4, wherein the controlling module is enabled for varying of the amount of flowing current through it in accordance with the touch location in order to differentiate touch zone and accordingly control the cooperative electronic application;
wherein, said controlling module preferably includes resistive circuits having one or more variable resistances each corresponding a touch location and connected to operational input means of the cooperative electronic application;
said supply voltage connected between the touchpad and the operational input means for supplying current through the external electronic circuit upon touching any of the touch location of the touchpad;
said variable resistances are tuned according to the touch location resistances of the touchpad enabling combined resistance of the touch location and the corresponding variable resistance high enough to flow of minimum required current to the operational input means in order to control the cooperative electronic application.
6. A touchpad device as claimed in anyone of claims 1 to 5, wherein the touchpad substrate preferably includes paper or any other material from commercially available transparent sheets (poly-vinyl alcohol), glass, natural polymers such as rubber or cellulosic fabrics, Perspex glass etc.;
wherein touchpad substrate made from paper and natural rubber will lead to an opaque touchpad and touchpad made from transparent poly-vinyl sheets can make it entirely transparent as well as flexible.

7. A touchpad device as claimed in anyone of claims 1 to 6, wherein the said conductive material coating includes graphite, graphene, metal, or conductive polymer; and the dielectric coating material and the dielectric spacer polymer material preferably PDMS, natural rubber, flexible nonconductive polymers.

8. A touchpad device as claimed in anyone of claims 1 to 7, configured for force or weight sensing comprises
said pair of flexible touchpad substrates having conductive and dielectric coating on either side and integrated together by stacking one touchpad substrate over another touchpad substrate such that the conductive material coated surfaces of the touchpad substrate pair faces each other;
said dielectric spacer decorated with holes in between the conductive coated surfaces to host the air gap between the conductive coated surfaces; and
a sensor for measuring output resistance of the touchpad device and change in the output resistance upon application of force / weight on the outer surface of the touchpad device to determine the force / weight wherein the applied force on outer surface of the touchpad substrate increases contact area of the conductive material coated inner surfaces causing monotonic reduction in the output resistance.
9. A touchpad device as claimed in claim 8, configured for detecting the pulse rate or heartbeat comprises said dielectric spacer in between the inner conductive coated surfaces of the touchpad substrates with only one hole corresponds to a single touch location one the touchpad to measure pressure generated by radial artery near the wrist location correlated to the pulse rate or heartbeat which push one of the conducting layers to make contact with the other and generates output resistance changing signal;
a sensor to measure output resistance changing signal.

10. A touchpad device as claimed in claim 9, configured for detecting neurological diseases like Parkinson’s comprises holding surface operatively connected to the single touch location;
said holding surface gripped by a person with fingers transfers the pressure generated from the fingers to the single touch location to detect fluctuation of the pressure causing from tremor in the fingers as reflected in the output electrical resistance measured by the sensor.
, Description:FIELD OF THE INVENTION:
The present invention is related to a simple touchpad device for different electronic applications. More specifically, the present invention is directed to develop an economic resistive touchpad device, which can be used as operation control/input device for a wide range of electronic applications such as mobile phones, computers, biomedical or healthcare appliances, fabrication/ characterization instruments and like.

BACKGROUND ART:
A touchpad is a sensitive surface that detects the location of touch area by detecting the variations in the electrical properties such as resistance, capacitance, inductance, or any other form of electrical or electronic signals. The touchpad devices can also be termed as sensors, which can detect the location of touch based on force or pressure applied on it and thereby based on the location of touch the touchpad devices generate electrical signal corresponding to the touch location which can be used for controlling a cooperative electronic application.

The touchpad devices can broadly be classified into capacitive and resistive types, wherein the resistive type touchpad devices are more preferred since these resistive touchpad devices are more affordable and durable.

In resistive type touchpad devices, output electrical resistance of the touchpad varies as different locations of said touchpad are touched. The existing commercially available resistive touchpad device consists of two resistive sheets sandwiching a dielectric material [Ref: US Patent No. US 8,717,313; US 8, 866,758 B2]. The outer resistive sheets are commonly made flexible for touch sensation while the inner one is made with a rigid material for the stability and longevity of the devices. While in operation, the flexible resistive sheet makes contact with the rigid one to generate output signal after receiving any touch sensation. The resistive touchpad devices can also be made up of only flexible substrates [Ref: US Patent No. US 7,439,962; US Patent Application No. US 2011/0199334].

It is important to note that, most of the commercially available resistive touchpad devices are rather costly because they employ either silicon or liquid crystal or flexible ITO based substrates for fabrication [Ref: US Patent Application No. 2002/0101407 A1; 2014/0023778 A1; 2012/0105359 A1].

Many of the commercially available resistive touchpad devices are composed of a glass or a polymer (acrylic) panel coated with a very thin indium tin oxide (ITO), which is an electrically conducting material [Ref: US Patent Application No. 2014/0023778 A1, US Patent Application No. 2012/0105359 A1]. In order to fabricate such devices costly lithography techniques and physical vapor deposition systems such as electron beam or thermal evaporation or sputtering techniques are mandatory. Further, the use of glass and ITO makes the commercially available touch pads rigid as well as costly.

Recent works have shown that low cost material such as paper can be employed to develop capacitive touchpad devices [Ref.: A. D. Mazzeo et al., Advanced Materials, 2012. 24(21): p. 2850-2856]. Touchpad devices with different materials like liquid crystal and of advanced multi touch capabilities are also reported [Ref.: US Patent Application No. 2013/0293809 A1, US Patent Application No. 2014/0023778 A1, US Patent 8,928,618 B2, US Patent Application No. 2013/0264179 A1, US Patent Application No. 2009/0109181 A1, US Patent 7,495,659 B2, US Patent 7,138,984 B1, US Patent 7,158,121 B2, US Patent 7,248,249 B2, US Patent Application No. 2007/0263165 A1]. However, the low cost and flexible resistive touchpad devices prepared from economic materials like paper is yet to make its appearance in the academic as well as technological parlance. This is an urgent need in the industry in order to serve the purpose of developing an economic touchpad device, which can be used for a wide range of applications such as mobile phones, computers, biomedical or healthcare appliances, fabrication/characterization instruments and like.

OBJECT OF THE INVENTION:
It is thus the basic object of the present invention to develop an economic touchpad device, which would be adapted to cooperate with wide range of electronic applications like mobile phones, computers, biomedical or healthcare appliances, fabrication / characterization instruments etc for controlling such electronic application.

Another object of the present invention is to develop a proof-of-concept economic and eco-friendly touchpad device adapted to be designed with commonly available materials such as paper, polydimethylsiloxane (PDMS), graphitic layers and like and fabricated without employing any costly equipment for fabrication and integration.

Yet another object of the present invention is to develop a touchpad device, which would be adapted to involve pair flexible touchpad substrate integrated in contactless disposition manner operating as switching point upon press based contact of the touchpad substrates in order to control cooperative wide range of electronic applications.

Another object of the present invention is to develop a resistive touchpad, which would be adapted to measure pressure, stress, force, or weight applied on the touchpad by detecting variation of the touchpad output electrical resistance due to the application of the pressure, stress, force, or weight.

Yet another object of the present invention is to develop a touchpad device, which would be adapted to operate as biomedical device for detecting pulse rate or heartbeat and neurological diseases like Parkinson’s diseases.

SUMMARY OF THE INVENTION:
Thus, according to the basic aspect of the present invention there is provided a touchpad device comprising
a pair of touchpad substrates, each touchpad substrate having conductive material coating on one side enabling electrical conductivity and dielectric material coating on opposite side for protective coating for hosting touch locations on said touchpad substrate;
said pair of touchpad substrates disposed one above the other such that the conductive material coated surface of one touchpad substrate faces towards of the conductive material coated surface of another touchpad substrate;
said conductive material coated surfaces of the touchpad substrates maintained in contactless disposition with at least one switching point of an air gap in between the conductive coated surfaces for touch and press based contact there between for the conducting coating of said touchpad substrates in said region for electrical conductivity and switching on connection and non-conducting and switching off disconnection on release of said press touch and press action.

According to another aspect in the present touchpad device, the pair of touchpad substrates comprises a dielectric spacer sandwiched within the conductive material coated surfaces to maintain the air gap;
said dielectric spacer is decorated with multiple holes to host the air gaps corresponding to the switching points and operate as targeted touch locations of the touchpad device.

According to yet another aspect in the present touchpad device, the conductive material coated side of the touchpad substrates include a metal connector to electronically connect said conductive material coated side of the touchpad substrates with an external controlling module and supply voltage associated with the touchpad device to facilitate controlling of a cooperative electronic application in accordance with touching of different location of the dielectric material coated side of the touchpad substrate.

According to another aspect in the present touchpad, the controlling module is enabled to receive current flow from the supply voltage specific to the touch location, when said touch location in the outer dielectric coated surface of the polymer substrate is touched and the polymer substrate bends at the touch location where the hole is decorated in the dielectric spacer and the conductive coating on the inner side of the touched polymer substrate came in contact with the conductive coating on the inner side of the untouched polymer substrate as the air gap between the graphite coated inner surfaces is vanished.

According to a further aspect in the present touchpad device, the controlling module is enabled for varying of the amount of flowing current through it in accordance with the touch location in order to differentiate touch zone and accordingly control the cooperative electronic application;
wherein, said controlling module preferably includes resistive circuits having one or more variable resistances each corresponding a touch location and connected to operational input means of the cooperative electronic application;
said supply voltage connected between the touchpad and the operational input means for supplying current through the external electronic circuit upon touching any of the touch location of the touchpad;
said variable resistances are tuned according to the touch location resistances of the touchpad enabling combined resistance of the touch location and the corresponding variable resistance high enough to flow of minimum required current to the operational input means in order to control the cooperative electronic application.
According to yet another aspect in the present touchpad device, the touchpad substrate preferably includes paper or any other material from commercially available transparent sheets (poly-vinyl alcohol), glass, natural polymers such as rubber or cellulosic fabrics, Perspex glass etc.;
wherein touchpad substrate made from paper and natural rubber will lead to an opaque touchpad and touchpad made from transparent poly-vinyl sheets can make it entirely transparent as well as flexible.

According to yet another aspect in the present touchpad device, the conductive material coating includes graphite or metal coating, conductive polymer coating; and the dielectric coating material and the dielectric spacer polymer material preferably PDMS, natural rubber, flexible nonconductive polymers.

According to a further aspect in the present touchpad device which is configured for force or weight sensing, comprises
said pair of flexible touchpad substrates having conductive and dielectric coating on either side and integrated together by stacking one touchpad substrate over another touchpad substrate such that the conductive material coated surfaces of the touchpad substrate pair faces each other;
said dielectric spacer decorated with holes in between the conductive coated surfaces to host the air gap between the conductive coated surfaces; and
a sensor for measuring output resistance of the touchpad device and change in the output resistance upon application of force / weight on the outer surface of the touchpad device to determine the force / weight wherein the applied force on outer surface of the touchpad substrate increases contact area of the conductive material coated inner surfaces causing monotonic reduction in the output resistance.
According to another aspect in the present touchpad device which is configured for detecting the pulse rate or heartbeat comprises said dielectric spacer in between the inner conductive coated surfaces of the touchpad substrates with only one hole corresponds to a single touch location one the touchpad to measure pressure generated by radial artery near the wrist location correlated to the pulse rate or heartbeat, which push one of the conducting layers to make contact with the other and generates output resistance changing signal;
a sensor to measure output resistance changing signal.

According to another aspect in the present touchpad device which is configured for detecting neurological diseases like Parkinson’s comprises holding surface operatively connected to the single touch location;
said holding surface gripped by a person with fingers transfers the pressure generated from the fingers to the single touch location to detect fluctuation of the pressure causing from tremor in the fingers as reflected in the output electrical resistance measured by the sensor.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 shows (a) structural configuration of outer surface of a preferred embodiment of the touchpad device in accordance with the present invention; (b) dielectric spacer layer used in the present touchpad device.
Figure 2 shows (a) an exploded view of a preferred embodiment of the present touchpad device; (b) side view of the present touchpad device with metallic connection to an external electrical circuits/applications; (c) structural transformation in the present touchpad device when the outer surface is pressed by a fingertip.
Figure 3 shows assembly of the components of a preferred embodiment of the present touchpad device with typical dimensions.
Figure 4(a)-(c) shows preferred electronic circuit embodiments associated with the present touchpad device for generating electrical signal corresponding to the touch location in the touchpad device for controlling a cooperative electronic application.
Figure 5(1)-(5) shows step-wise illustration of the operation of the present touchpad device.
Figure 6 shows optical microscopic images of (A) cross-section of graphite coated paper where the graphite layer and paper are mentioned in the image and (B) FESEM image of graphite film.
Figure 7 shows (A) force sensitivity for different kind of papers where the resistance is changing with the applied weight and (B) output resistance variation with applied weight for different touch layer thickness.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:
The present invention discloses a novel low cost and flexible resistive touchpad devices prepared from low cost material. More specifically, the present invention discloses a proof-of-concept resistive touchpad prepared from paper, PDMS, and graphite.
A preferred touchpad device embodiment of the present invention basically includes a pair of flexible touchpad substrates having conductive and dielectric coatings on either side and integrated together by stacking one touchpad substrate over another touchpad substrate such that the conductive material coated surfaces of the touchpad substrate pair faces each other.
The conductive material, which preferably includes graphite or graphene coating, is made on one side of the touchpad substrate to instill electrical conductivity to that touchpad substrate. The dielectric coating preferably includes a coating of dielectric thin film of polymeric material such as PDMS on the side of aforementioned touchpad substrate which does not have the graphite coating. The PDMS coating on the touchpad substrate provides a protective coating for hosting the touch locations.
In the present device embodiment, a pair of such graphite and PDMS coated touchpad substrates are integrated together in a stacked manner so that, the graphite coated surface of one touchpad substrate of the pair faces to the graphite coated surface of another touchpad sheet of the pair having an air gap in between the graphite coated surfaces. The PDMS coated surfaces of the pair of touchpad substrates remain outside. In the stacked arrangement of the touchpad substrates, it is ensured that the conductive material coated surfaces i.e. the graphite coated surfaces of the touchpad substrates maintained in contactless disposition with at least one switching point corresponding to the air gap in between the conductive coated surfaces for touch and press based contact there between for the conducting coating of said touchpad substrates in said region for electrical conductivity and switching on connection and non-conductivity and switching off disconnection on release of said press touch and press action.

The air gap between the graphite coated surfaces is maintained with the help of a dielectric spacer, which is sandwiched within the conductive material coated surfaces of the substrates. The dielectric spacer is decorated with multiple holes to host these air gaps, which are also the targeted touch locations of the touchpad device.
A controlling module and a supply voltage external to the touchpad device is operatively connected with said touchpad device in such a manner that, when the touch location in the outer PDMS coated surface of the touchpad substrate is touched, the touchpad substrate bends at the touch location where a hole is decorated in the dielectric spacer and the graphitic layers on the inner side of the touched touchpad substrate came in contact with the graphitic layers on the inner side of the untouched touchpad substrate as the air gap between the graphite coated inner surfaces is vanished, electrical current flows to the controlling module from the supply voltage through the connected graphitic layers specific to the ‘touch’ location. The controlling module associated with the touchpad device is enabled for varying of the amount of flowing current in accordance with the locations of ‘touch’ in order to differentiate the ‘touch’ zone and accordingly control a cooperative electronic application.
In the present innovation, the touchpad substrate preferably includes paper since it is among the most commonly available materials. Waste newspapers, commercially available transparent sheets (poly-vinyl alcohol) and natural rubber can be alternatively used instead of the commercial paper for fabricating the touchpad substrate. While the waste newspaper, commercial paper, and natural rubber will lead to an opaque touchpad and the transparent poly-vinyl sheets can make it entirely transparent as well as flexible.
The touchpad substrate may also include other low-cost materials like say OHP sheets made of polyester. The transparent PDMS polymer can also replace paper. Moreover, the graphite coating can also be replaced by some other conducting materials.
Reference is now invited from the accompanying figure 1, which shows structural configuration of outer paper surface and dielectric spacer layer used in the present touchpad device.

The accompanying figure 1(a) schematically shows the preparation of the confining paper surfaces (101) in which the outer side of the paper is coated with a PDMS thin film (102), inner side is coated with a graphite layer (103) issuing out of a pencil tip, and at the side of the paper a metallic connector (104) is fabricated, which electronically connects the graphite layer with the external electric circuit. Figure 1(b) shows the typical dielectric PDMS spacer (105) used in the present touchpad device, in which there are four holes (106) targeted for four specific touch locations.

Reference is next invited from the accompanying figure 2(a), which shows an exploded view of a preferred embodiment of the present touchpad device. As shown in the figure 2(a), that the pair of paper surfaces (101T (this is not visible from this angle) and 101B) having PDMS (102T and 102B) and graphite coating (103T and 103B) are assembled with a dielectric PDMS spacer (105) with four holes (106).

The accompanying figure 2(b) shows the side view of the assembly in which the metal connectors (104) on the components 103T and 103B are connected to the external controlling module having the supply voltage (201), a resistance (202), and a LED - light emitting diode (203). The figure 2(b) also shows the side view of the holes in the PDMS spacer (106), necessary for the preparation of the touchpad device. The accompanying figure 2(c) schematically shows how the graphite coated inner surfaces (103T and 103B) came in contact with each other when the outer PDMS films (102T) are pressed by a fingertip, which led to switching of the LED (203).

The assembly of the components with typical dimensions is shown in the figure 3. The figure shows the top paper layer (101T) with a conductive graphite coating in the inner surface (103T), a PDMS thin film coating on the outer surface (102T), and a copper connect (104). In this figure, the non-conducting PDMS film (102T) with targeted square spaces (301) intended for the touch locations. The holes in the inner PDMS spacer (105) were placed exactly underneath these zones. One corner of the fabricated touchpad is zoomed in and the top and bottom PDMS layer (102T and 102B) are shown along with the spacer layer (105) sandwiched in between component 102T and 102B.
Reference is next invited from the accompanying figure 4, which shows a preferred electronic circuit embodiment the present controlling module to facilitate controlling of corresponding electronic application based on touching of different region of the present touchpad device. In the present circuit representation, the LEDs are used to explain the generation of the electrical signal corresponding to the touch location in the touchpad device for controlling the cooperative electronic application based on touching of different region of the present touchpad. In actual application, the LEDs can be replaced with the operational input means of the cooperative electronic application.
As shown in the accompanying figure 4 (a), the external controlling module, which is enabled for varying of the amount of flowing current in accordance with the locations of ‘touch’ in order to differentiate the ‘touch’ zone and accordingly control the cooperative electronic application, is a resistive circuit. The circuit embodiment of the accompanying figure 4 (a) includes variable resistances R1 to R4 connected to the LEDs L1 to L4, respectively, which are tuned according to the touch area resistances R5 to R8 of the touchpad. The switches S1 to S4 represent each touch area in the touchpad for which the touch area resistances are R5 to R8. The supply voltage VS is connected in-between touchpad and LED, as shown in circuit.
As mentioned in above each touch location has a particular output resistance and each touch location is connected to LEDs using some variable resistances. When anyone touch one location, current flows from power supply to the target LED(s) from the touch locations to the variable resistances. If the combined resistance of a touch location and the corresponding target variable resistance are high then less current would flow through that channel. The external variable resistance is tuned in such a manner that minimum required current flows through the circuit in order to turn on the target LED.
To illustrate the tuning of the resistance further, an example of touchpad having two touch locations A and B (Figure 4(b) and (c)) may be considered. If the minimum current to lit a LED is 0.3 mA and the circuit as shown in Figure 4(b) and 4(c) is designed in such a manner so that when touch area S1 is pressed as shown in Figure 4(b), then LED L1 glows and LED L2 remains turned off and when touch area S2 is pressed as shown in Figure 4(c) then both the LEDs glow and to achieve this, the resistances R1 and R2 are tuned in such a manner that, R1 = 5 k? and R2 = 10 k?. The resistance of the different touch locations are RA = 10 k?, RB = 5 k? and the supply voltage is VS = 9 V. It is assumed that the LEDs do not have any internal resistance in order to reduce the complexity.
From circuit theory, the total current through RA when S1 is pressed can be given by,
Similarly for the S2 the current
Now, when S1 is pressed, thus the total current is I1.
Now in this condition the current through R1 is
Similarly the current through R2 is,
If all the values of the above mentioned resistance are put in the above equations then I1 = 0.675 mA, I11 = 0.45 mA and I12 = 0.225 mA. Thus, in this case only the L1 LED is turned on. Again, if the S2 is pressed then I2 = 1.08 mA, I21 = 0.72 mA and I22 = 0.36 mA. Thus in this case both the LEDs are turned on.

Experimental images in the figure 5 show that the LED glows depending on ‘touch’ position.
• Case 1 shows the setup and 4 touch positions namely a, b, c, and d.
• Case 2 shows that all LEDs are turned on once touch is made in first location.
• Case 3 shows that only 3 LEDs are turned on once touch is made in the second location.
• Case 4 shows that only 1 LED is turned on once touch is made in the third location.
• Case 5 shows that all LEDs are turned off once touch is made in fourth location.
The optical microscopic and FESEM images are shown in the Fig. 6. The thickness of the conductive layer which is chosen to be graphite here, on paper is ~10 µm as shown in optical microscopic image in Fig. 6(A).The FESEM image of graphite coating on paper is also shown in Fig. 6(B).
A preferred embodiment of the present touchpad device can be used as force or weight sensor because its output resistance changed with the application of force on the touchpad substrate. The present resistive touchpad device embodiment, which is configured for sensing force or weight may include said pair of flexible touchpad substrates having conductive and dielectric coating on either side and integrated together by stacking one touchpad substrate over another touchpad substrate such that the conductive material coated surfaces of the touchpad substrate pair faces each other. The resistive touchpad device embodiment for sensing force or weight further includes the dielectric spacer decorated with holes in between the conductive coated surfaces to host the air gap between the conductive coated surfaces and a sensor for measuring output resistance of the touchpad device and change in the output resistance upon application of force / weight on the outer surface of the touchpad device to determine the force / weight since the applied force on outer surface increases contact area of the conductive material coated inner surfaces causing monotonic reduction in the output resistance.
It may be noted here that the sensitivity of the touchpad device depends on the material of touchpad substrate and the thicknesses of the touchpad substrate. The thickness of the touchpad substrate can be adjusted to set the range of detectable force or weight. Calculation of force can also give the stress or pressure applied, which is defined as the force per unit area. The accompanying figure 7 shows force sensitivity for different kind of (A) paper based touchpad substrate where the resistance (R) is changing with the applied weight (W) and image (B) shows how output resistance (R) also changes with applied weight (W) for different touchpad thickness.
The present touchpad device can also be applied as bio-medical device for detecting the pulse rate or heartbeat. Since, the present touchpad device is capable of detecting force as discussed earlier and to apply this in bio-medical devices for detecting the pulse rate or heartbeat, the touchpad device is modified so that the dielectric spacer in between the inner conductive coated surfaces of the touchpad substrates includes only one hole corresponds to a single touch location on the touchpad which is used to measure the pressure generated by radial artery near the wrist location. During the heart contraction a wave is generated due to the pumping of blood from heart under pressure. The wave travels along the walls of arteries, which appears as a soft pulse near the wrist and can be measured. This pressure can push one of the conducting layers to make contact with the other similarly as described in Figure 2(C) and thus it can generate output resistance changing signal at the output which can be measured and correlated to the pulse rate or strength by using a sensor.
This innovation also can be applied in detecting neurological diseases like Parkinson’s disease. With suitable modifications, the grabbing force or maximum pressure exerted by the fingers can be monitored through the reported methodology once a person press or grabs it. The single touch location of the touchpad as discussed previously is operative connected to a holding surface. If a person holds the holding surface with his/her fingers then the pressure generated from the fingers can be detected by measuring the output resistance changing signal. If there is any tremor in the fingers of the user then there will be fluctuation of pressure and the pressure fluctuation will be reflected in the output electrical resistance measured by the sensor. Thus the neurological disorders can easily be detected by measuring the variation of the holding pressure or output resistance of the sensors.