Claims:1. A device to measure mechanical stretch (100), with a capacitance range of between 50pF and 1,500pF and a sensitivity of 4pF/mm, comprising:

at least one dielectric film layer (101), said at least one dielectric film layer (101) being a dielectric elastomer made of Silicone material and being sandwiched between fabric electrode layers (102a and 102b), said fabric electrode layers (102a and 102b) being silver coated fabric electrodes, with the device (100) being mounted with a fabric (103) on both its ends; and a coaxial cable (104) that is associated with the device (100) and facilitates the sending/receiving of signals to/from the device (100), with the at least one dielectric film layer (101) being configured to be stretchable up to 400% and the fabric electrode layers (102a and 102b) being configured to be stretchable up to 300%.

2. The device to measure mechanical stretch (100), with a capacitance range of between 50pF and 1,500pF and a sensitivity of 4pF/mm, as claimed in claim 1, wherein the Silicon material is Silicone rubber.

3. The device to measure mechanical stretch (100), with a capacitance range of between 50pF and 1,500pF and a sensitivity of 4pF/mm, as claimed in claim 1, wherein the fabric used in the electrode layers (102a and 102b) and the fabric (103) used to mount the device (100) are spandex based fabrics.

4. The device to measure mechanical stretch (100), with a capacitance range of between 50pF and 1,500pF and a sensitivity of 4pF/mm, as claimed in claim 1, wherein the length of the device (100) is 9 centimetres, the thickness of the device (100) is 2 centimetres, and the length and width of the fabric (103) used to mount the device (100) on either side are 3 centimetres and 5 centimetres, respectively.
, Description:TITLE OF THE INVENTION: A DEVICE TO MEASURE MECHANICAL STRETCH
FIELD OF THE INVENTION
The present disclosure is related to a device to measure mechanical stretch.
BACKGROUND OF THE INVENTION
A sensor is a device that is used to detect events or changes in its environment and send the information to other electronic devices. Conventionally, sensors are classified based on the parameter they sense. Sensors may also be classified based on the transduction mechanisms they employ. The commercially available sensors include temperature sensors, pressure sensors, flow sensors, stress/strain sensors, accelerometers, dielectric sensors, conductivity sensors, shock sensors, and vibration sensors.
Similarly, a wide range of sensor technologies like Piezo-resistive sensors, accelerometers/gyros, and Camera systems, are available for measuring the mechanical stretch. Devices capable of measuring larger strains or displacements are usually much more complex.
All these technologies have many drawbacks. Piezo-resistive sensors lack precision and are highly environmentally sensitive, and accelerometers drift at low frequency. Camera systems require structured environments with controlled lighting. Great inroads can be made with sensor fusion, for example global positioning systems or camera systems for dynamic calibration, drift of accelerometers can be mitigated using magnetometers. But these are complex and potentially obtrusive and bulky to wear.
There is, therefore, a need in the art for a device to measure mechanical stretch, which overcomes the aforementioned problems and drawbacks.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a device to measure mechanical stretch, in accordance with an embodiment of the present disclosure.
Figure 2 illustrates the dimensions of construction of a device to measure mechanical stretch, in accordance with an embodiment of the present disclosure.
Figure 3(a) and Figure 3(b) illustrate a device to measure mechanical stretch in relaxed state and stretched state, respectively, in accordance with the present disclosure.
Figure 4 illustrates the change in capacitance on stretching a device to measure mechanical stretch, in accordance with the present disclosure.
SUMMARY OF THE INVENTION
A device to measure mechanical stretch, with a capacitance range of between 50pF and 1,500pF and a sensitivity of 4pF/mm is disclosed. Said device comprises at least one dielectric film layer, said dielectric film layer being a dielectric elastomer made of Silicone material and being sandwiched between fabric electrode layers, said fabric electrode layers being silver coated fabric electrodes. The device is mounted with a fabric on both its ends. A coaxial cable is associated with the device and facilitates the sending/receiving of signals to/from the device.
The dielectric film layer is configured to be stretchable up to 400% and the fabric electrode layers are configured to be stretchable up to 300%.
The Silicone material used is Silicone rubber with: tensile strength 6.2 N/mm2; tear strength 10N/mm; elongation at break 470%; operating temperature range -50°C to 220°C; permittivity 3; dielectric strength 90 V/µm to 105 V/µm; volume resistivity 1014 ohm/cm, and thickness of 50 µm.
The fabric used in the electrode layer and the fabric used to mount the device are spandex based fabrics.
The device is highly stretchable; repeatable; easy to integrate with any real-time system; flexible; delivers rapid response; highly sensitive; economical; robust; wireless capable; washable; thin and lightweight; durable; requires low operating power; comfortable; and perfect for wearable devices.
The device can be used in human-activity monitoring; medical diagnostics; health monitoring; wearable devices; smart garments; virtual/augmented reality systems; soft robotics; entertainment; sports and fitness industry for tracking human motions.
DETAILED DESCRIPTION OF THE INVENTION
Throughout this specification, the use of the word "comprise" and “include” and variations such as "comprises "comprising", “includes”, and “including “implies the inclusion of an element or elements not specifically recited.
Throughout this specification, the disclosure of any range is to be construed as being inclusive of the lower limit of the range and the upper limit of the range.
A device to measure mechanical stretch (100) is disclosed. As illustrated in Figure 1 and Figure 2 the device to measure mechanical stretch (100) comprises at least one dielectric film layer (101) that is sandwiched between fabric electrode layers (102a and 102b), said device (100) being mounted with a fabric (103) on both its ends; and a coaxial cable (104) that is associated with the device (100) and facilitates the sending/receiving of signals to/from the device (100).
In an embodiment of the present disclosure, the at least one dielectric film layer (101) is a dielectric elastomer made of Silicone material. Said Silicone material is highly elastic, and has very low viscoelastic and stress relaxation effect. The Silicone material used is Silicone rubber with: tensile strength 6.2 N/mm2; tear strength 10N/mm; elongation at break 470%; operating temperature range -50°C to 220°C; permittivity 3; dielectric strength 90 V/µm to 105 V/µm; volume resistivity 1014 ohm/cm, and thickness of 50 µm.
In another embodiment of the present disclosure, the fabric electrode layers (102a and 102b) are silver coated fabric electrodes, which do not lose conductivity even after washing. Silver is compliant with movable silicone particles. It has favourable contacts with the dielectric elastomer surface. Another advantage of using silver coated fabric electrodes is that of good conductivity at cheap and commercially viable prices. Softness (low hardness), and high resistance to oxidation make silver an excellent choice for contact materials. The silver coated fabric electrodes have the characters of radiation protection, antisepsis, and pollution suppression, and, hence, protect human health.
In yet another embodiment of the present disclosure, the fabric used in the electrode layer (102a and 102b) and the fabric (103) used to mount the device (100) are spandex based fabrics.
In yet another embodiment of the present disclosure, both the at least one dielectric film layer (101) and the fabric electrode layers (102a and 102b) are made of flexible and stretchable materials. The at least one dielectric film layer (101) is configured to be stretchable up to 400% and the fabric electrode layers (102a and 102b) are configured to be stretchable up to 300%.
In yet another embodiment of the present disclosure, the thickness of the at least one dielectric film layer (101) is 2 centimetres.
In yet another embodiment of the present disclosure, the thickness of each fabric electrode layer in the fabric electrode layers (102a and 102b) is 0.2 centimetres.
In yet another embodiment of the present disclosure, the length and width of the fabric (103) used to mount the device (100) on either side are 3 centimetres and 5 centimetres, respectively.
In yet another embodiment of the present disclosure, the length of the device (100) is 9 centimetres and the thickness is 2 centimetres.
In yet another embodiment of the present disclosure, the capacitance range of the device (100) is between 50pF and 1,500pF and the sensitivity of the device (100) is 4pF/mm.
The working principle of the device (100) shall now be explained with the help of Figure 3(a) and Figure 3(b).
As the at least one dielectric film (101) is strained, it thins and expands in area, increasing its capacitance, which increases its energy capacity in just milliseconds. As illustrated in Figure 3(a) and Figure 3(b) the capacitance of the device (100) varies on stretching, due to change in area and thickness.
The capacitance of the device (100) can be calculated from below mentioned formula:

Where,
er is dielectric constant
e0 is permittivity of free space
A is active polymer area
t is the thickness of the at least one dielectric film (101)
Cparasitic is the capacitance caused by contact (can be neglected)
The electrical specifications of the disclosed device (100) are as follows:

Parameters Value Unit Notes
Base Capacitance 860 pF Capacitance at relaxed state
Linearity 99.9 % R2 value of data conformation to linear trend line
Sensitivity 4 pF/mm -
Cable Length 500 mm Coax cable
The change in capacitance on stretching the device (100) is illustrated in Figure 4.
The device (100) disclosed in the present disclosure is highly stretchable; repeatable; easy to integrate with any real-time system; flexible; delivers rapid response; highly sensitive; economical; robust; wireless capable; washable; thin and lightweight; durable; requires low operating power; comfortable; and perfect for wearable devices.
The device (100) disclosed in the present disclosure can be used in human-activity monitoring; medical diagnostics; health monitoring; wearable devices; smart garments; virtual/augmented reality systems; soft robotics; entertainment; sports and fitness industry for tracking human motions.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations and improvements without deviating from the spirit and the scope of the disclosure may be made by a person skilled in the art. Such modifications, additions, alterations and improvements should be construed as being within the scope of this disclosure.
LIST OF REFERENCE NUMERALS:
100 – A Device to Measure Mechanical Stretch
101 – At least One Dielectric Film Layer
102(a), 102(b) – Fabric Electrode Layers
103 – Device Mounting Fabric
104 – Coaxial Cable