Preparation method of three-layer self-healing flexible strain sensor

Abstract

A preparation method of a three-layer self-healing flexible strain sensor includes steps of: preparing an encapsulating layer composite, so as to obtain a concentrated solution; preparing a strain sensitive layer composite, so as to obtain a thick liquid; dropping the thick liquid on a glass substrate, and statically curing at a room temperature; dropping the concentrated solution on a cured film obtained in the S3, and statically curing at the room temperature; striping a cured filmed obtained in the S4 from the glass substrate, and drawing out two wires as electrodes; and dropping the concentrated solution on the other surface of the cured film obtained in the S3 with a same amount of S4, and statically curing at the room temperature for obtaining the three-layer self-healing flexible strain sensor. The three-layer self-healing structure strain sensor can be prepared without using a repair agent, but can achieve rapid self-repair.

Claims

1. A method of producing a three-layer self-healing flexible strain sensor comprising a first encapsulating layer, a strain sensitive layer, and a second encapsulating layer, the method comprising: S1: preparing an encapsulating layer composition; S2: preparing a strain sensitive layer composition; S3: dropping the strain sensitive layer composition on a glass substrate and statically curing the strain sensitive layer composition at room temperature to produce the strain sensitive layer having a first surface and a second surface; S4: dropping a first amount of the encapsulating layer composition on the first surface of the strain sensitive layer, and statically curing the first amount of the encapsulating layer composition at room temperature to produce the first encapsulating layer; S5: removing the strain sensitive layer and the first encapsulating layer from the glass substrate; and S6: dropping a second amount of the encapsulating layer composition on the second surface of the strain sensitive layer and statically curing the second amount of the encapsulating layer composition at room temperature to produce the second encapsulating layer, wherein: the first amount of the encapsulating layer composition and the second amount of the encapsulating layer composition are the same; the first encapsulating layer, the strain sensitive layer, and the second encapsulating layer each have self-healing function; preparing the strain sensitive layer composition comprises: S201: preparing a conductive composite solution or a doped carbon material solution, and S202: heating the conductive composite solution or the doped carbon material solution to 60-90° C., then stirring for 20-30 min to evaporate solvent and thicken the conductive composite solution or the doped carbon material solution, so as to produce the strain sensitive layer composition; preparing the conductive composite solution comprises: adding 40-50 ml of tetrahydrofuran into a reaction flask, then adding 0.1-0.2 g polydopamine (PDA) and 0.05-0.1 g ferric chloride (FeCl.sub.3) in sequence, putting a magnetic stir bar into the reaction flask, and placing the reaction flask on a magnetic stirrer to stir with 400-500 r/min for 8-12 h, or adding 40-50 ml of tetrahydrofuran into a reaction flask, then adding 1 g polyacrylic acid (PAA), 0.2-0.33 g hydroxy-terminated polydimethylsiloxane, 0.1-0.2 g polydopamine (PDA), and 0.05-0.1 g ferric chloride (FeCl.sub.3) in sequence, putting a magnetic stir bar into the reaction flask, and placing the reaction flask on a magnetic stirrer to stir with 400-500 r/min for 8-12 h; and preparing the doped carbon material solution comprises: adding 40-50 ml tetrahydrofuran into a reaction flask, then adding 0.8 g-1 g polyacrylic acid (PAA), 0.1-0.2 g polydopamine (PDA) and 0.02-0.05 g carbon material in sequence, putting a magnetic stir bar into the reaction flask, and placing the reaction flask on a magnetic stirrer to stir with 400-500 r/min for 8-12 h, or adding 1 g polyacrylic acid (PAA), 0.2-0.33 g hydroxy-terminated polydimethylsiloxane (PDMS), 0.1-0.2 g polydopamine (PDA) and 0.02-0.05 g carbon material in sequence, putting a magnetic stir bar into the reaction flask, and placing the reaction flask on a magnetic stirrer to stir with 400-500 r/min for 8-12 h.

2. The method as recited in claim 1, wherein preparing the encapsulating layer composition comprises: S101: adding 40-50 ml tetrahydrofuran into a reaction flask, then adding 0.8-1 g polyacrylic acid (PAA), 70-86 mg N,N′-dicyclohexylcarbodiimide (DCC) and 50-56 mg 4-(dimethyl)aminopyridine (DMAP) in sequence; putting a magnetic stir bar into the reaction flask and placing the reaction flask on a magnetic stirrer to stir with 400-500 r/min for 1-2 h; S102: adding 0.2-0.33 g hydroxy-terminated polydimethylsiloxane (PDMS) into the reaction flask, sealing, and magnetically stirring at room temperature for 8-12 h to produce a solution; and S103: heating the solution to 60-90° C., then stirring for 20-30 min to evaporate solvent and concentrate the solution, so as to produce the encapsulating layer composition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a sectional view of a three-layer self-healing flexible strain sensor of the present invention.

(2) FIG. 2 is a sketch view of a self-healing flexible strain sensor according to an embodiment 3 of the present invention applying to a wrist in a relax state.

(3) FIG. 3 is a sketch view of the self-healing flexible strain sensor according to the embodiment 3 of the present invention applying to the wrist in a bending state.

(4) FIG. 4 illustrates a three-time repair test of the self-healing flexible strain sensor according to the embodiment 3 of the present invention.

(5) Element reference: 1—self-healing encapsulating layer, 2—self-healing sensitive layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(6) Referring to FIGS. 1-4 of the drawings, the present invention will be further illustrated.

(7) A three-laver self-healing flexible strain sensor is provided, comprising: a self-healing sensitive layer 2, wherein a self-healing encapsulating layer 1 is respectively placed on an upper surface and a lower surface of the self-healing sensitive layer 2. The self-healing encapsulating layer 1 comprises: 0.2-0.33 parts by weight of hydroxyl-terminated polydimethylsiloxane (PDMS), 0.8-1 parts by weight of polyacrylic acid (PAA), 0.070-0.086 parts by weight of N,N′-dicyclohexylcarbodiimide (DCC) and 0.050-0.056 parts by weight of 4-(dimethyl)aminopyridine (DMAP).

(8) The self-healing sensitive layer comprises a doped carbon material or a conductive composite.

(9) The doped carbon material comprises 0.8-1 parts by weight of polyacrylic acid (PAA), 0.1-0.2 parts by weight of polydopamine (PDA), and 0.02-0.05 parts by weight of a carbon material; or 1 part by weight of polyacrylic acid (PAA), 0.2-0.33 parts by weight of hydroxyl-terminated polydimethylsiloxane (PDMS), 0.1-0.2 parts by weight of polydopamine (PDA), and 0.02-0.05 parts by weight of the carbon material. The carbon material is selected from a group consisting of graphene, reduced graphene oxide, graphene quantum dots, graphene nano-platelets, carbon nano-tubes, and carbon nano-fibers.

(10) The conductive composite comprises 0.8-1 parts by weight of polyacrylic acid (PAA), 0.1-0.2 parts by weight of polydopamine (PDA) and 0.05-0.1 parts by weight of ferric chloride (FeCl.sub.3); or 1 part by weight of polyacrylic acid (PAA), 0.2-0.33 parts by weight of hydroxy-terminated polydimethylsiloxane, 0.1-0.2 parts by weight of polydopamine (PDA), and 0.05-0.1 parts by weight of ferric chloride (FeCl.sub.3).

(11) The present invention also provides a preparation method of a three-layer self-healing flexible strain sensor, comprising steps of:

(12) S1: preparing a self-healing encapsulating layer composite, so as to obtain a concentrated solution;

(13) wherein the S1 specifically comprises steps of:

(14) S101: adding 40-50 ml tetrahydrofuran into a reaction flask, then adding 0.8-1 g polyacrylic acid (PAA), 70-86 mg N,N′-dicyclohexylcarbodiimide (DCC) and 50-56 mg 4-(dimethyl)aminopyridine (DMAP) in sequence; putting a magnetic stir bar into the reaction flask and placing the reaction flask on a magnetic stirrer to stir with 400-500 r/min for 1-2 h;

(15) S102: adding 0.2-0.33 g hydroxy-terminated polydimethylsiloxane (PDMS) into the reaction flask, sealing and magnetically stirring at the room temperature for 8-12 h; and

(16) S103: heating a solution obtained in the S102 to 60-90° C., then stirring for 20-30 min for evaporating a solvent till the solution is concentrated, so as to obtain the concentrated solution;

(17) S2: preparing a self-healing sensitive layer composite, so as to obtain a thick liquid;

(18) wherein the S2 specifically comprises steps of:

(19) S201: preparing a conductive composite solution, which comprises steps of adding 40-50 ml tetrahydrofuran into a reaction flask, then adding 0.1-0.2 g polydopamine (PDA) and 0.05-0.1 g ferric chloride (FeCl.sub.3); or 1 g polyacrylic acid (PAA), 0.2-0.33 g hydroxy-terminated polydimethylsiloxane, 0.1-0.2 g polydopamine (PDA) and 0.05-0.1 g ferric chloride (FeCl.sub.3) in sequence; putting a magnetic stir bar into the reaction flask and placing the reaction flask on a magnetic stirrer to stir with 400-500 r/min for 8-12 h;

(20) or preparing a doped carbon material solution, which comprises steps of adding 40-50 ml tetrahydrofuran into a reaction flask, then adding 0.8 g-1 g polyacrylic acid (PAA), 0.1-0.2 g polydopamine (PDA) and 0.02-0.05 g carbon material; or 1 g polyacrylic acid (PAA), 0.2-0.33 g hydroxy-terminated polydimethylsiloxane (PDMS), 0.1-0.2 g polydopamine (PDA) and 0.02-0.05 g the carbon material in sequence; and

(21) S202: heating a solution obtained in the S201 to 60-90° C., then stirring for 20-30 min for evaporating a solvent till the solution is thick, so as to obtain the thick liquid;

(22) S3: dropping the thick liquid on a glass substrate, and statically curing at a room temperature;

(23) S4: dropping the concentrated solution on a cured film obtained in the S3, and statically curing at the room temperature;

(24) S5: striping a cured filmed obtained in the S4 from the glass substrate, and drawing out two wires as electrodes; and

(25) S6: dropping the concentrated solution on the other surface of the cured film obtained in the S3 with a same amount of S4, and statically curing at the room temperature for obtaining the three-layer self-healing flexible strain sensor.

Embodiment 1

(26) The present invention uses the doped carbon material to form the self-healing sensitive layer, and a preparation method of the three-layer self-healing flexible strain sensor comprises specific steps of:

(27) S1: adding 40 ml tetrahydrofuran into a first reaction flask, then adding 0.8 g polyacrylic acid (PAA), 70 mg N,N′-dicyclohexylcarbodiimide (DCC) and 55 mg 4-(dimethyl)aminopyridine (DMAP) in sequence; putting a magnetic stir bar into the first reaction flask and placing the first reaction flask on a magnetic stirrer to stir with 400-500 r/min for 2 h; adding 0.2 g hydroxy-terminated polydimethylsiloxane (PDMS) into the first reaction flask, sealing and magnetically stirring at the room temperature for 12 h; and heating the solution to 90° C., then stirring for 20 min for evaporating a solvent till the solution is concentrated, so as to obtain the concentrated solution;

(28) S2: adding 40 ml tetrahydrofuran into a second reaction flask, then adding 0.8 g polyacrylic acid (PAA), 0.25 g polydopamine (PDA) and 0.1 g carbon nano-tubes (CNTs); putting a magnetic stir bar into the second reaction flask and placing the second reaction flask on a magnetic stirrer to stir with 400-500 r/min for 12 h; heating a solution obtained to 90° C., then stirring for 20 min for evaporating a solvent till the solution is thick, so as to obtain the thick liquid;

(29) S3: dropping the thick liquid on a clean glass substrate, and statically curing at a room temperature for 1 h;

(30) S4: dropping the concentrated solution on a cured film obtained in the S3, and statically curing at the room temperature for 1 h;

(31) S5: striping a cured filmed obtained in the S4 from the glass substrate, and drawing out two wires as electrodes; and

(32) S6: dropping the concentrated solution on the other surface of the cured film obtained in the S3 with a same amount of S4, and statically curing at the room temperature for obtaining the three-layer self-healing flexible strain sensor.

(33) The three-layer self-healing flexible strain sensor prepared in the embodiment 1 has good tensile properties and conductive properties, which can be quickly repaired after being destroyed under room temperature conditions, and maintain good performance of the original sensor.

Embodiment 2

(34) The present invention uses the conductive composite to form the self-healing sensitive layer, and a preparation method of the three-layer self-healing flexible strain sensor comprises specific steps of:

(35) S1: adding 40 ml tetrahydrofuran into a first reaction flask, then adding 1 g polyacrylic acid (PAA), 86 mg N,N′-dicyclohexylcarbodiimide (DCC) and 60 mg 4-(dimethyl)aminopyridine (DMAP) in sequence; putting a magnetic stir bar into the first reaction flask and placing the first reaction flask on a magnetic stirrer to stir with 400-500 r/min for 2 h; adding 0.2 g hydroxy-terminated polydimethylsiloxane (PDMS) into the first reaction flask, sealing and magnetically stirring at the room temperature for 12 h; and heating the solution to 90° C., then stirring for 20 min for evaporating a solvent till the solution is concentrated, so as to obtain the concentrated solution;

(36) S2: adding 40 ml tetrahydrofuran into a second reaction flask, then adding 0.8 g polyacrylic acid (PAA), 0.2 g polydopamine (PDA) and 0.1 g ferric chloride (FeCl.sub.3); putting a magnetic stir bar into the second reaction flask and placing the second reaction flask on a magnetic stirrer to stir with 400-500 r/min for 12 h; heating a solution obtained to 90° C., then stirring for 20 min for evaporating a solvent till the solution is thick, so as to obtain the thick liquid;

(37) S3: dropping the thick liquid on a clean glass substrate, and statically curing at a room temperature for 1 h;

(38) S4: dropping the concentrated solution on a cured film obtained in the S3, and statically curing at the room temperature for 1 h;

(39) S5: striping a cured filmed obtained in the S4 from the glass substrate, and drawing out two wires as electrodes; and

(40) S6: dropping the concentrated solution on the other surface of the cured film obtained in the S3 with a same amount of S4, and statically curing at the room temperature for obtaining the three-layer self-healing flexible strain sensor.

(41) The three-layer self-healing flexible strain sensor prepared in the embodiment 2 has good tensile properties and conductive properties, which can be quickly repaired after being destroyed under room temperature conditions, and maintain good performance of the original sensor.

Embodiment 3

(42) The present invention uses the conductive composite to form the self-healing sensitive layer, and a preparation method of the three-layer self-healing flexible strain sensor comprises specific steps of:

(43) S1: adding 40 ml tetrahydrofuran into a first reaction flask, then adding 1 g polyacrylic acid (PAA), 86 mg N,N′-dicyclohexylcarbodiimide (DCC) and 50 mg 4-(dimethyl)aminopyridine (DMAP) in sequence; putting a magnetic stir bar into the first reaction flask and placing the first reaction flask on a magnetic stirrer to stir with 400-500 r/min for 2 h; adding 0.25 g hydroxy-terminated polydimethylsiloxane (PDMS) into the first reaction flask, sealing and magnetically stirring at the room temperature for 2 h; and heating the solution to 90° C., then stirring for 20 min for evaporating a solvent till the solution is concentrated, so as to obtain the concentrated solution;

(44) S2: adding 40 ml tetrahydrofuran into a second reaction flask, then adding 1 g polyacrylic acid (PAA), 0.1 g polydopamine (PDA) and 0.04 g ferric chloride (FeCl.sub.3); putting a magnetic stir bar into the second reaction flask and placing the second reaction flask on a magnetic stirrer to stir with 400-500 r/min for 12 h; heating a solution obtained to 90° C., then stirring for 20 min for evaporating a solvent till the solution is thick, so as to obtain the thick liquid;

(45) S3: dropping the thick liquid on a clean glass substrate, and statically curing at a room temperature for 1 h;

(46) S4: dropping the concentrated solution on a cured film obtained in the S3, and statically curing at the room temperature for 1 h;

(47) S5: striping a cured filmed obtained in the S4 from the glass substrate, and drawing out two wires as electrodes; and

(48) S6: dropping the concentrated solution on the other surface of the cured film obtained in the S3 with a same amount of S4, and statically curing at the room temperature for obtaining the three-layer self-healing flexible strain sensor.

(49) The three-layer self-healing flexible strain sensor prepared in the embodiment 3 has good tensile properties and conductive properties, which can be quickly repaired after being destroyed under room temperature conditions, and maintain good performance of the original sensor.

(50) The strain sensor in embodiments 1-3 were cut into two sections with a blade after being tested and cut with a blade, wherein the two sections were placed in a fitted state, and the repair effect was observed and recorded (as in the following table).

(51) TABLE-US-00001 conductivity stretchability repairability embodiment 1 2.1 MΩ ~140% within 30 s sufficient at room temperature embodiment 2 320 KΩ ~150% within 30 s sufficient at room temperature embodiment 3 530 KΩ ~180% within 30 s sufficient at room temperature

(52) The embodiment 3 was applied to the real-time monitoring of the human body movement state before and after the repair (as shown in FIG. 2-3). According to experimental results, the Keithley 4200-SCS signal collector was used to collect the resistance data, so as to monitor resistance change response diagram of wrist bending after different repair times. Referring to test curves of three different repair times in FIG. 4, the repaired three-layer self-healing flexible strain sensor still maintains good performance such as stability, response, and reproducibility. In addition, the three-layer self-healing flexible strain sensor can be used for real-time monitoring of the human body's small deformation physical activity (i.e. breathing or pulse) and movement state (i.e. joint bending).

(53) One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.

(54) It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.