Flexible finger photoelectric hardness sensor

Abstract

The utility model provides a kind of flexible finger photoelectric hardness sensor, including chip, flexible finger and substrate, chip includes the lower substrate layer being arranged on the upper surface of substrate, LED light ray emitting module being arranged on the lower substrate layer, PD light ray receiving module being arranged on the lower substrate layer, P electrode, N electrode and sapphire upper substrate layer;LED light ray emitting module, PD light ray receiving module are respectively conducted with corresponding P electrode and N electrode, and PD light ray receiving module is distributed in the circumference of LED light ray emitting module, and sapphire upper substrate layer is arranged on the upper surface of LED light ray emitting module and PD light ray receiving module;Flexible finger is arranged on the upper surface of substrate, and chip is located between flexible finger and substrate.PD light ray receiving module receives and feedback photoelectric current intensity in close range, utilizes the linear relationship between the hardness of object and photoelectric current intensity, test accurate, equipment volume is small, and anti-interference ability is strong.

Description

Technical Field

[0001] This utility model relates to the field of hardness testing, and in particular to a photoelectric hardness sensor for flexible fingers. Background Technology

[0002] Tactile perception is an essential way for humans to acquire information about the external environment and the properties of objects, and the perception of object hardness is an extremely important method of information acquisition. The human body has very limited ability to perceive and distinguish hardness, and human skin has limited resistance to bacteria and contaminants in the external environment, making it impossible to freely touch all objects and accurately, quickly, and effectively determine their hardness. Hardness sensors can replace human fingers and skin, quickly and accurately acquiring object hardness information and feeding it back to humans, helping them perceive the hardness properties of objects and avoid potential harm. As a highly important type of sensor, hardness sensors play a crucial role in food safety testing, intelligent robots, and medical and health diagnostics, demonstrating promising application prospects.

[0003] Currently, research on hardness sensors is limited. Dedicated hardness testers are expensive to produce, and commercial Shore hardness testers, for example, rely solely on the pressure generated by gravity, resulting in low measurement accuracy. Traditional piezoresistive sensors have a wide detection range but are greatly affected by external temperature. Electromagnetic sensors are susceptible to external magnetic fields and exhibit poor stability. Some existing fiber-optic-based hardness sensors can address the problems of traditional pressure sensors, offering advantages such as small size, light weight, electrical insulation, and immunity to environmental interference. However, the fabrication process and structure of optical fibers are relatively complex, leading to high production costs. Furthermore, the fiber only serves as a light transmission channel; separate light emission and reception modules are required for complete detection functionality, resulting in a large overall device size and hindering integration with other devices. Therefore, there is an urgent need for a precise, compact, flexible finger photoelectric hardness sensor. Utility Model Content

[0004] In order to overcome the shortcomings of the existing technology, the purpose of this utility model is to provide a flexible finger photoelectric hardness sensor that is accurate in testing and small in size.

[0005] The objective of this utility model is achieved through the following technical solution:

[0006] A flexible finger photoelectric hardness sensor includes a chip, a flexible finger, and a substrate. The chip includes a lower substrate layer disposed on the upper surface of the substrate, an LED light emitting module disposed on the lower substrate layer, a PD light receiving module disposed on the lower substrate layer, a P electrode, an N electrode, and a sapphire upper substrate layer. The LED light emitting module and the PD light receiving module are respectively connected to the corresponding P electrode and N electrode. The PD light receiving modules are distributed around the LED light emitting module. The sapphire upper substrate layer is disposed on the upper surface of the LED light emitting module and the PD light receiving module. The flexible finger is disposed on the upper surface of the substrate, and the chip is located between the flexible finger and the substrate.

[0007] Preferably, the substrate is provided with a power input interface and a light intensity signal output interface, and the P electrode and N electrode are electrically connected to the power input interface.

[0008] Preferably, a cavity is left between the flexible finger and the sapphire substrate.

[0009] Preferably, the flexible finger is made of PDMS material.

[0010] Preferably, an ITO current spreading layer is provided on the upper surface of the lower substrate layer.

[0011] Preferably, a Bragg reflector is provided on the lower surface of the substrate layer.

[0012] Preferably, the PD light receiving modules are arranged in a ring shape, and the LED light emitting module is located in the middle of the ring-shaped PD light receiving modules.

[0013] Preferably, a mask pattern is provided between the PD light receiving module and the LED light emitting module.

[0014] Compared with existing flexible finger photoelectric hardness sensors, the flexible finger photoelectric hardness sensor of this invention has the following advantages:

[0015] By integrating the PD light receiving module with the LED light emitting module, an object presses on a flexible finger, changing the contact area between the flexible finger and the sapphire substrate. This alters the effective refractive index at the interface between the flexible finger and the sapphire substrate. The PD light receiving module receives and feeds back the photocurrent intensity at close range. Utilizing the linear relationship between the object's hardness and the photocurrent intensity, the test is accurate, the device is small in size, and has strong anti-interference capabilities. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the chip for the flexible finger photoelectric hardness sensor of this utility model.

[0017] Figure 2 This is a schematic diagram of the structure of the flexible finger photoelectric hardness sensor of this utility model.

[0018] Figure 3 This is a schematic diagram illustrating the working principle of the flexible finger photoelectric sensor of this utility model.

[0019] Figure 4 This is a standard curve showing the relationship between photocurrent intensity and hardness.

[0020] Figure 5 This is a schematic diagram of the distribution structure of the LED light emitting module and the PD light receiving module. Wherein: 10, chip; 101, sapphire upper substrate layer; 102, LED light emitting module; 103, PD light receiving module; 104, lower substrate layer; 105, P electrode; 106, N electrode; 20, substrate; 201, power input interface; 202, light intensity signal output interface; 30, flexible finger; 40, object. Detailed Implementation

[0021] To make the technical problem solved by this utility model, the technical solution adopted, and the technical effect achieved clearer, the technical solution of the embodiments of this utility model will be further described in detail below. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0022] like Figure 1-4 This embodiment provides a flexible finger photoelectric hardness sensor, including a chip 10, a flexible finger 30, and a substrate 20. The chip 10 includes a lower substrate layer 104 disposed on the upper surface of the substrate 20, an LED light emitting module 102 disposed on the lower substrate layer 104, a PD light receiving module 103 disposed on the lower substrate layer 104, a P electrode 105, an N electrode 106 disposed on the lower substrate layer 104, and a sapphire upper substrate layer 101. The LED light emitting module 102 and the PD light receiving module 103 are respectively connected to the corresponding P electrode 105 and N electrode 106. The PD light receiving modules 103 are distributed around the LED light emitting module 102. The sapphire upper substrate layer 101 is disposed on the upper surface of the LED light emitting module 102 and the PD light receiving module 103. The flexible finger 30 is disposed on the upper surface of the substrate 20, and the chip 10 is located between the flexible finger 30 and the substrate 20. The substrate 20 is provided with a power input interface 201 and a light intensity signal output interface 202. The P electrode 105 and the N electrode 106 are electrically connected to the power input interface 201. A cavity is left between the flexible finger 30 and the sapphire substrate layer 101.

[0023] Working principle: The substrate 20 of the photoelectric hardness sensor is fixed to the moving shaft of the stepper motor. The object to be tested 40 is placed on the platform of the stepper motor and aligned with the center of the cavity. The LED light emitting module 102 and the PD light receiving module 103 are powered on and start working. The stepper motor is started, and the moving shaft of the stepper motor drives the photoelectric hardness sensor to move down gradually until the surface of the flexible finger 30 contacts the object 40, and the interaction force between the two reaches 2N. At this time, the photocurrent detected by the PD light receiving module 103 is 32uA. The stepper motor continues to move down, and the cavity of the flexible finger 30 is compressed. The inner side of the flexible finger 30 contacts the surface of the sapphire substrate layer 101. The effective refractive index of the light emitted by the LED light emitting module 102 changes at the contact surface between the flexible finger 30 and the sapphire substrate layer 101, and the light is emitted. The PD light receiving module 103 receives the corresponding reflected light and feeds back the photocurrent intensity. By comparing it with the pre-derived standard curve of photocurrent intensity and hardness, the hardness of the object 40 can be obtained. When in contact with objects 40 of different hardness, the contact area between the flexible finger 30 and the sapphire substrate layer 101 is different, and the effective refractive index of light at the contact surface is also different.

[0024] The power input interface 201 and the light intensity signal output interface 202 on the substrate 20 are respectively connected to the power supply and the light intensity signal display.

[0025] To improve the deformation accuracy of the flexible finger 30 and the sapphire substrate 101, the flexible finger 30 is made of PDMS material. The PDMS flexible finger 30 deforms quickly and accurately when stress changes.

[0026] An ITO current spreading layer is provided on the upper surface of the lower substrate 104.

[0027] A Bragg reflector is provided on the lower surface of the substrate 104. To improve testing accuracy, the light from the LED light emitting module 102 is reflected by the Bragg reflector and then reflected onto the sapphire upper substrate 101, ensuring the consistency of optical parameters in the testing environment.

[0028] like Figure 5 As shown, in order to fully capture the reflected light, the PD light receiving module 103 is arranged in a ring structure, and the LED light emitting module 102 is located in the middle of the ring-shaped PD light receiving module 103.

[0029] To prevent the light emitted by the LED light emitting module 102 from being captured by the PD light receiving module 103 without being reflected by the sapphire substrate 101, a mask pattern is provided between the PD light receiving module 103 and the LED light emitting module 102 to block the side light of the LED light emitting module 102.

[0030] Fabrication method of flexible finger photoelectric hardness sensor:

[0031] S1. A 6μm thick LED epitaxial structure composed of InGaN / GaN multiple quantum wells (mqw) was grown on the lower surface of a 4-inch sapphire substrate 10110 using metal-organic chemical vapor deposition (MOCVD) technology, and an LED light emitting module 102 and a PD light receiving module 103 were set accordingly.

[0032] S2. A 0.12 μm thick indium tin oxide (ITO) layer was deposited on the p-GaN surface as a current spreading layer;

[0033] S3. Define a mask pattern with a spacing of 10μm between the LED light emitting module 102 and the PD light receiving module 103, and etch the exposed GaN spacing onto the sapphire substrate layer 10110 using ICP.

[0034] S4. P electrode 105 and N electrode 106 with a thickness of 1.65 μm were evaporated on the exposed current spreading layer and n-GaN, respectively.

[0035] S5. A 0.36 μm thick SiO2 passivation treatment is performed using plasma-enhanced chemical vapor deposition to form the lower substrate layer 104.

[0036] S6. A 3.16 μm thick SiO2 / TiO2 Bragg mirror was prepared using an optical coating machine.

[0037] S7. After rapid annealing, the sapphire substrate 101 is thinned to 150μm by grinding and polishing to form chip 10.

[0038] S8. To make a PDMS grooved membrane with a cavity, the ratio of curing agent to PDMS (polydimethylsiloxane) is 1:7.5 (high hardness). Pour the prepared PDMS gel into a small sample box. After the PDMS is spread evenly in the sample box, use a dropper to drop water droplets into the PDMS and heat to cure. The water droplets will evaporate during the heating process. After curing, a grooved PDMS membrane will be formed.

[0039] S9. Use double-sided tape to fix the substrate 20 onto the sample box, take out the PDMS film obtained in the first step, align the groove structure with the chip 10 and flip it onto the substrate 20.

[0040] S10. Cut the tip of the dropper to make a finger-shaped mold shell and fit it onto the substrate 20 with the PDMS groove film.

[0041] S11. Fill the sample box with PDMS gel again (the ratio of curing agent to PDMS is 1:7.5), then heat and cure it. After the PDMS is completely cured, perform the demolding process to obtain the flexible finger photoelectric hardness sensor.

[0042] The above embodiments are only some preferred embodiments of this utility model and should not be used to limit the scope of protection of this utility model. Any non-substantial changes and substitutions made by those skilled in the art based on this utility model shall fall within the scope of protection claimed by this utility model.

Claims

1. A flexible finger photoelectric hardness sensor, comprising a chip, a flexible finger, and a substrate, characterized in that, The chip includes a lower substrate layer disposed on the upper surface of the substrate, an LED light emitting module disposed on the lower substrate layer, a PD light receiving module disposed on the lower substrate layer, a P electrode, an N electrode, and a sapphire upper substrate layer; the LED light emitting module and the PD light receiving module are respectively connected to the corresponding P electrode and N electrode, the PD light receiving modules are distributed around the LED light emitting module, and the sapphire upper substrate layer is disposed on the upper surface of the LED light emitting module and the PD light receiving module; the flexible finger is disposed on the upper surface of the substrate, and the chip is located between the flexible finger and the substrate.

2. The flexible finger photoelectric hardness sensor according to claim 1, characterized in that, The substrate is provided with a power input interface and a light intensity signal output interface, and the P electrode and N electrode are electrically connected to the power input interface.

3. The flexible finger photoelectric hardness sensor according to claim 1, characterized in that, A cavity is left between the flexible finger and the sapphire substrate.

4. The flexible finger photoelectric hardness sensor according to claim 1, characterized in that, The flexible finger is made of PDMS material.

5. The flexible finger photoelectric hardness sensor according to claim 1, characterized in that, An ITO current spreading layer is provided on the upper surface of the lower substrate layer.

6. The flexible finger photoelectric hardness sensor according to claim 1, characterized in that, The lower surface of the substrate layer is provided with a Bragg reflector.

7. The flexible finger photoelectric hardness sensor according to claim 1, characterized in that, The PD light receiving modules form a ring structure, and the LED light emitting module is located in the middle of the ring-shaped PD light receiving modules.

8. The flexible finger photoelectric hardness sensor according to claim 7, characterized in that, A mask pattern is provided between the PD light receiving module and the LED light emitting module.

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