CN111543665B

CN111543665B - Microwave-induced 4D printer and application thereof

Info

Publication number: CN111543665B
Application number: CN202010387087.8A
Authority: CN
Inventors: 张慜; 郭超凡
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2020-05-09
Filing date: 2020-05-09
Publication date: 2021-04-20
Anticipated expiration: 2040-05-09
Also published as: CN111543665A

Abstract

The invention discloses a 4D printer induced by microwaves and application thereof, and belongs to the technical field of food processing. The microwave bin positioned on the 4D printing platform mainly comprises a microwave leakage-proof bin made of microwave shielding materials and a microwave field generating device arranged on the lower portion of the platform. Wherein, the microwave leak-proof bin can move along with the printer nozzle and is connected through the soft microwave leak-proof material. Microwave energy generated by the microwave solid-state source is transmitted to a rotating antenna arranged on the side of the microwave leakage-proof bin through a coaxial cable to coat the microwave energy. The microwave power is adjustable, and the temperature of the object is controllable. The printed article can be induced by a microwave field in the microwave bin, and real-time 4D spontaneous change occurs in the printing process. Meanwhile, a prediction model of 4D spontaneous change is established to realize controllable change. The printer can be used for realizing 4D printing of spontaneous changes of food color, fragrance and shape under microwave induction. And the accuracy of the prediction model can reach 90-95%.

Description

Microwave-induced 4D printer and application thereof

Technical Field

The invention relates to a microwave-induced 4D printer and application thereof, and belongs to the technical field of food processing.

Background

So-called 4D printing, precisely a material that is capable of automatic deformation, with only specific conditions (such as temperature, humidity, etc.) and without any need to connect any complex electromechanical devices, allows a fourth dimensional change to be made according to the product design, which usually involves color, flavor and shape. Khoo et al (2015) propose 4D printing as a process of building physical objects using appropriate additive manufacturing techniques, laying down a series of stimulus responsive composite or multi-materials with different properties. After construction, the object reacts to stimuli from the natural environment or through human intervention, resulting in changes in the physical or chemical state over time.

Heat treatment, an essential processing means in food processing, is an ideal stimulation condition for 4D printing of food. Microwave field heating is more efficient and heats more uniformly than conventional heat sources. The microwave field has more interaction mechanisms as a stimulation condition with the corresponding dielectric stimulus responsive material. The microwave field in combination with the dielectric material can provide more, more precise "programming" and control space than conventional thermal stimuli. Therefore, the introduction of the microwave field into the 4D printing of the food as a stimulus provides new ideas and means for the high efficiency and controllability of the 4D printing of the food. In the invention, the microwave field generating and controlling device is attached to a printing platform of a food printer, and provides a stable and continuous microwave field for an object printed by the printer to be used as a 4D change stimulus source, so that the printed object is prompted to generate real-time spontaneous 4D change again on the basis of 3D printing, and the concept of 4D printing is met.

37154, wintersweet et al (2018) invented a printing device (publication number: CN109049675A) for 3D food models, which solves the problem of low applicability of the prior art. The device includes frame, compounding mechanism and printing mechanism, and above-mentioned compounding mechanism and printing mechanism all connect in the frame, compounding mechanism can carry the printing raw materials after mixing to printing mechanism department, and 3D food model of setting for the shape can be printed out to above-mentioned printing mechanism. This 3D food model's printing device suitability is than higher. Zhanhong et al (2018) disclose a 3D food printing system (publication No. CN109042788A), the 3D food printing system comprises a feeder, a tray feeding conveyor, a 3D printer, a moving assembly and a tray discharging conveyor, when in use, the feeder continuously conveys raw materials into the 3D printer, the tray feeder conveys a tray to the moving assembly below the 3D printer, and when the tray is conveyed to the moving assembly through the tray feeding conveyor, the 3D printer prints the raw materials conveyed from the feeder into a specific three-dimensional shape on the tray. After printing, the tray is conveyed out by the tray-out conveyor belt, so that the full-automatic printing process of food forming is realized. This 3D printing system can accomplish a series of processes such as feed, send the dish, print and play dish in the food production process, and the course of working need not shut down reinforced, consequently can realize the continuous processing to food raw materials, has improved food machining efficiency and processingquality. Zhanhong et al (2018) disclose a collaborative precision nutritional food 3D printing system and method (publication No.: CN 109007945A). This 3D printing system includes conveyer, many 3D food printer, spare parts subassembly and six robots. The invention relates to a collaborative accurate nutritional food 3D printing system and a collaborative accurate nutritional food 3D printing method, wherein the system is a food 3D printer system cooperatively matched with six-axis robots, and the six-axis robots can complete automatic replacement of multiple charging barrels and automatic discharging of food models according to preset memorized positioning points, so that balanced food nutrition collocation and full automation of food 3D printing production are realized. Simultaneously, adopt many food 3D printers of conveyer belt cooperation to form the assembly line operation that accurate nutrition food 3D printed processing to can require layering subregion according to the raw materials ratio of accurate nutrition food and flow line preparation in proper order, realized the automated processing that the accurate nutrition 3D printed food was constructed by multiple food raw materials. Different from the above inventions, the printer in the invention is a 4D printer with microwave cooperation. The printer can realize real-time 4D spontaneous change through microwave field induction while 3D printing is carried out.

The petrology intelligence (2018) discloses a microwave-assisted 3D food printing device and method (publication number: CN109363221A), and the microwave-assisted 3D food printing device comprises a 3D printing box body, wherein a scanning area and a mixing area are respectively arranged above the inside of the 3D printing box body, a cooling area and a printing area are respectively arranged below the scanning area and the mixing area, an abrasive device and a storage tank are respectively arranged on two sides of the upper end of the 3D printing box body, a feeding port of the storage tank is arranged above the mixing area, and a computer digital control panel is arranged on one side of the 3D printing box body. The scanning district of setting, can scan food, wait for object external structure shape, can imitate according to the scanning shape and print in printing, the compounding district of setting can carry out the homogeneous mixing to the material that falls into in the storage tank, promote printing efficiency, the cooling space of setting is used for food to print the back, carry out cooling treatment to food as required, the food surface after making the printing solidifies, prevent to warp, the computer digital control panel of setting is used for setting for printing the parameter, this device, moreover, the steam generator is simple in structure, high durability and convenient operation, and is suitable for extensive popularization. Different from the invention, the material extrusion unit is an extrusion unit based on a piston principle, and can be linked with the microwave shielding unit to ensure that the material can avoid damaging the machine body and the control unit while receiving the interference of a stable microwave field.

Yanhao Li (2018) discloses an intelligent thermoelectric heating spray head (publication number: CN209346074U) of a food 3D printer, which comprises a nozzle, a CPU central control system, a feed delivery pipe, an extrusion device and a semiconductor refrigerating and heating device, wherein the feed delivery pipe, the extrusion device and the semiconductor refrigerating and heating device are respectively connected with the CPU central control system, the extrusion device is connected with the top of the feed delivery pipe, the bottom of the feed delivery pipe is connected with the semiconductor refrigerating and heating device, the nozzle is arranged at the inner side of the bottom of the feed delivery pipe, the semiconductor refrigerating and heating device comprises semiconductor refrigerating sheets arranged around the bottom of the feed delivery pipe, the semiconductor refrigerating sheets comprise a refrigerating end, a semiconductor cold end guide strip, an N-type semiconductor area, a P-type semiconductor area, a semiconductor hot end guide strip and a heating end which are sequentially arranged, the heating end is connected with the feed delivery pipe, and the. Compared with the prior art, the utility model has the advantages of solved shower nozzle heating problem, accelerated the cooling of printing the model after the nozzle ejection of compact, reduce the energy consumption, improve the cost of printing the precision, reducing food output. Different from the invention, the invention mainly relates to a microwave generating device which is a 4D food printer and has a heat source of 20-200W, and is continuously and linearly controllable at 2450 MHz.

Fig. schel K shaa (2018) discloses a method of treating a three-dimensionally printed object using microwave radiation (publication No.: CN 106794628A). The method for processing a three-dimensional printed object in such a method may include: the method includes providing a three-dimensional printed object formed from a printing mixture comprising a solidifiable matrix and a microwave absorber dispersed in the solidifiable matrix, and applying a focused input of microwave radiation to the printed object at one or more locations. Application of microwave radiation heats the microwave absorber at one or more locations and promotes consolidation of the printing mixture within the printed object. First, the method is mainly applied to non-food materials, and thus can disperse a microwave absorber in a printing material. On the contrary, the printing material in the method is a food material which can originally absorb the microwave, and the invention discloses a 4D printer and application, not a simple application method.

Vandamin et al (2019) disclose a food microwave three-dimensional printing method and a printer (publication number: CN 109820224A). the invention realizes the effect of instant curing of extruded materials by releasing microwaves at the front end through a microwave heating probe embedded in the inner wall of a charging barrel and combining the size setting of non-wave-absorbing materials; the heating efficiency of the product is effectively improved and microwave leakage and diffusion are prevented by designing the bell mouth and the choke groove of the leakage-proof unit and combining with the wave-absorbing material design of the printing platform; the microwave is generated by the microwave solid-state source and is conducted by the transmission line, so that the microwave output is stable, the power and the frequency can be adjusted according to the printing requirement, and the microwave solid-state source is small in size and convenient to integrate; the mode of heating curing makes the product structure mechanical strength who prints out high through the limit printing, can realize the preparation of cavity unsupported spatial structure, and the product molding is difficult for collapsing. Different from the invention, the microwave field is integrated on the printing platform of the 3D printer, and the microwave field can be stably and continuously provided for printing materials. The microwave shielding unit of the present invention is different from the microwave leakage preventing unit of the present invention in the operation mechanism. The microwave field in the present invention is mainly applied to the whole printing platform, and the microwave in the present invention is mainly applied to the vicinity of the nozzle. Therefore, the microwave field on the 3D printer platform has the capability of realizing the real-time 4D spontaneous change of the printed object.

Zhang 24924et al (2019) disclose a microwave-assisted three-dimensional printing device and an accurate and efficient printing method for a plant gel system (application number: 2019110028646), wherein the device comprises a three-dimensional printer, a built-in real-time microwave heating and curing device, a flexible microwave shielding box body, an embedded online microwave real-time controller and the like. The microwave source is a solid microwave source, and the power is continuously adjustable within the range of 20-200W. Microwave energy feedback is realized by adopting a rotary antenna mode, and the microwave can be uniformly absorbed by the material layer in the printing process. The device can realize the real-time heating solidification of printing in-process microwave at 3D, reaches the fast curing and improves and print the precision, shortens 3D under the full flow and prints the efficiency of production food. According to the material properties (such as rheological property and dielectric property), a matching relation is established between the printing extrusion speed of the material and the microwave real-time heating power in the 3D printing process, so that the material is cured at a proper speed, the printing precision of more than 95% is realized, and the material is not deformed in the subsequent process. Different from the reported device, the microwave field generated by the microwave solid-state source is transmitted to the lightweight rotary antenna positioned on the side surface of the fixed microwave shielding case through the coaxial cable and is uniformly coated in the whole microwave shielding case, so that the printing precision can be ensured to the maximum extent while the movement of the platform in the Y-axis direction is not influenced. The invention also discloses three microwave-catalyzed 4D printing methods, including deformation 4D printing, color-changing 4D printing and aroma-changing 4D printing, which are different from the purposes and implementation means of high-efficiency curing mentioned in the report.

Disclosure of Invention

The invention provides a stable microwave field for a printing platform on the basis of an extrusion type food 3D printing system to catalyze the real-time 4D spontaneous change of a printed object.

The technical scheme of the invention is as follows:

A4D printer induced by microwaves comprises a printing Cartesian coordinate driving unit, a material extruding unit, a microwave field output unit, a microwave field leakage preventing unit and a control unit 13; the material extrusion unit comprises a charging barrel, a charging barrel microwave shielding sleeve 7 and a microwave shielding printing nozzle 6; the microwave field output unit comprises a microwave solid source 1 and a rotary antenna coating rod 3; the microwave field leakage prevention unit comprises a fixed microwave shielding cover 4, an X-axis movable microwave shielding cover 8 and a Z-axis movable microwave shielding cover 5; the control unit 13 includes a microwave output power controller, a temperature measuring device, and a temperature controller.

Further, in the material extrusion unit, the charging barrel microwave shielding sleeve 7 is of a 304 stainless steel hollow structure, and can be placed in the charging barrel and shield a microwave field; the microwave shielding printing spray head 6 is in a 304 stainless steel structure, can be connected with the charging barrel through a screw, and has selectable nozzle diameters of phi 0.8, 1.2 and 1.5 mm.

Further, the microwave field output unit is arranged outside the 4D printer; wherein, the power supply power of the microwave solid source 1 is 500VA, 220V/50Hz, the output frequency is 2450MHz, the microwave energy can be accurately controlled, the continuous linear adjustment of the power of 20-200W can be realized, the control is accurate, and the reproducibility is good; the rotary antenna coating rod 3 is a microwave output device which is positioned on the side surface of the fixed microwave shielding case 4, and a stable and uniform microwave field is ensured to be provided in the microwave shielding bin where the printed object is positioned. Microwave energy generated by the microwave solid state source 1 is transmitted to the rotating antenna coating rod 3 via the coaxial cable 16.

Furthermore, the microwave field leakage-proof units are all made of 304 stainless steel, wherein the fixed micro-structure is arranged in the microwave field leakage-proof unitsThe wave shield 4 is fixed on the food 4D printer base; the Z-axis moving microwave shielding cover 5 is fixed on an X-axis moving slide bar 11 of the 4D printer and can move along the X-axis moving slide bar 11; the X-axis movable microwave shielding cover 8 is fixed on a material extrusion unit sliding block 10 and can move along the X axis with the material extrusion unit; adopting a structure for resisting current and preventing microwave leakage between different shielding cases (<1mw/cm²) And the influence of microwave leakage on other units and the damage to operators are avoided.

Furthermore, the microwave output power controller in the control unit 13 can realize that the microwave output power is continuously, linearly and accurately adjustable within 20-200W; the temperature measuring device 17 adopts an infrared online temperature measuring sensor, can display the temperature of the printed workpiece in real time, and has a temperature measuring range of 0-500 ℃; the control unit 13 is connected with the temperature measuring device 17 and the microwave source 1, and can realize the regulation and control of the microwave output of the microwave source within the control range of temperature.

The invention also provides a food 4D printing method using microwave induction, which comprises the following steps:

1) selecting proper printing parameters and the diameter of the microwave shielding printing nozzle 6 according to the rheological property and the type of the material to be printed;

2) setting the microwave output power and induced spontaneous change processing time of the microwave field output unit;

3) and 4D printing is carried out on the material to be printed according to the printing model.

A third object of the present invention is to provide a 4D printed prediction model of microwave-induced spontaneous deformation, discoloration and aroma, comprising:

1) temperature calculation of the printed article in the microwave field: calculating the temperature of each layer of the printed object in the microwave field according to an electromagnetic wave equation and a heat conduction equation, and calculating the value of the temperature T according to the following formula:

wherein, P is the power received by the printed object in the microwave field; epsilon₀Is the relative dielectric constant of electromagnetic waves in vacuum; ε' is the dielectric loss factor of the printed material; e is the electric field strength; omega is angular frequency; ρ is the print density, c_pIs the specific heat capacity of the printed material; t is the temperature of the printed object; t is time; k is the thermal conductivity of the printing material; f is the frequency of the microwaves generated by the microwave source.

2) Deformation model: and (4) adopting a Matlab tool and calling a BP neural network module to establish a three-layer BP neural network model. Setting algorithm parameters: the number of concealment layers is 10, and the training method is Levenberg-Marquardt. Setting an input layer as 1) to obtain the derived object temperature and microwave heating time; the output layer is a deformation bending angle. Inputting the selected training sample into a BP neural network, training the BP neural network, comparing the output value of the BP neural network with an actually measured value until the mean square error of the BP neural network training meets the requirement, and determining the weight and the threshold value of each layer of the BP neural network.

3) Color change model: and (4) adopting a Matlab tool and calling a BP neural network module to establish a three-layer BP neural network model. Setting algorithm parameters: the number of concealment layers is 10, and the training method is Levenberg-Marquardt. Setting an input layer as 1) to obtain the derived object temperature and microwave heating time; the output layer is the Lab color difference value compared to the original color. Inputting the selected training sample into a BP neural network, training the BP neural network, comparing the output value of the BP neural network with an actually measured value until the mean square error of the BP neural network training meets the requirement, and determining the weight and the threshold value of each layer of the BP neural network.

4) Fragrant change model: and programming by adopting Matlab language, and calling a BP neural network module to establish a three-layer BP neural network model. Setting algorithm parameters: the number of concealment layers is 10, and the training method is Levenberg-Marquardt. Setting an input layer as 1) to obtain the derived object temperature and microwave heating time; the output layer is the signal value of the target flavor substance measured by GC-MS. Inputting the selected training sample into a BP neural network, training the BP neural network, comparing the output value of the BP neural network with an actually measured value until the mean square error of the BP neural network training meets the requirement, and determining the weight and the threshold value of each layer of the BP neural network.

The invention has the beneficial effects that:

the invention provides a 4D printer and a method utilizing microwave induction, which can effectively realize the 4 th dimensional change of a food printing object under the catalysis of a microwave field; the microwave printing system integrates a small-dose microwave generating device and a coating system on a traditional food printing platform, and realizes a stable microwave field in a microwave shielding cabin which can move along with a Cartesian coordinate driving unit of a printer so as to test that a printed object can generate real-time 4D spontaneous changes (color, fragrance and type spontaneous changes). And the 4D spontaneous change in the invention can be predicted by a model, so that the programmable 4D printing is realized.

Drawings

FIG. 1 is a schematic illustration of the present invention.

In the figure: the device comprises a microwave solid source 1, a printing platform 2, a rotary antenna coating rod 3, a fixed microwave shielding cover 4, a movable microwave shielding cover 5Z axis, a shielded printing nozzle 6 microwave, a microwave shielding sleeve of a charging barrel 7, a movable microwave shielding cover 8X axis, a printed object 9, an extrusion unit slider 10, a movable sliding rod 11X axis, an extrusion piston 12, a control unit 13, a charging barrel A14, a charging barrel B15, a coaxial cable 16 and a temperature measuring device 17.

Detailed Description

The following is a further description of the invention with reference to specific examples.

Example 1: multi-layer spontaneous deformation 4D printing of wheat dough and oat fiber dough

Mixing wheat flour with water according to the weight ratio of 2.5: 1, mixing uniformly to prepare a wheat dough layer material, and filling the wheat dough layer material into a charging barrel A14. Mixing oat fiber powder, wheat starch and water according to the weight ratio of 2.5: 1: 2.5 mixing uniformly to prepare the oat fiber dough layer material, and filling the oat fiber dough layer material into a charging barrel B15. Selecting a microwave shielding printing nozzle 6 of a charging barrel A14 with the diameter of 1.2 mm; the diameter of the microwave shielding print head 6 of the cartridge B15 was selected to be 1.5 mm. The printing distance was set to 1.5mm and the moving speed of the head was set to 30 mm/s. The input printing model can control the two materials to be alternately stacked in the printing process. Performing model prediction according to a designed target 4D deformation result, and setting the output microwave power of a microwave field generating device (a microwave solid-state source 1 and a rotary antenna coating rod 3) to be 120W according to input parameters of a prediction model; the temperature of the control unit 13 was set to 80 ℃. Because the wheat dough layer can be dehydrated and shrunk during the microwave field treatment, the oat fiber dough layer can not be shrunk due to dehydration. Under the induction of 120W microwave field, the temperature of the printed article is controlled by the control unit 13 to float within the range of 80 +/-3 ℃. The printed wheat dough/oat fiber dough alternately superposed printed article can be subjected to layer-by-layer real-time spontaneous 4D deformation bending within 20min due to shrinkage difference of each layer, and bending deformation within a range of 15-90 degrees can be realized. Finally, the overall deformation precision can reach more than 90% of the model predicted value.

Example 2: wheat dough spontaneous color-changing 4D printing

Mixing edible soybean oil and pigment oil according to the weight ratio of 9: 1, mixing uniformly to prepare the diluted pigment oil. 1% gum arabic aqueous solution, 1% gelatin aqueous solution and diluted pigment oil were mixed in a 50: 50: 1, and dispersing at 3000 rpm for 3 min. After dispersing evenly, adjusting the pH value to 4 by using 1% acetic acid aqueous solution, and then stirring at constant speed for 30min in a water area at 4 ℃. Standing after stirring, and layering. Taking out the precipitate, and freeze-drying at-80 deg.C under 220Pa for 22 hr to obtain the color-changing powder.

Mixing wheat flour with water according to the weight ratio of 2.5: 1, mixing uniformly to prepare a wheat dough layer material, and filling the wheat dough layer material into a charging barrel A14. Mixing wheat flour with water according to the weight ratio of 2.5: 1, mixing, adding 1% color-changing powder (w/w), and filling into barrel B15. Selecting a microwave shielding printing nozzle 6 of a charging barrel A14 with the diameter of 1.2 mm; the diameter of the microwave shielding print head 6 of the cartridge B15 was selected to be 1.2 mm. The printing distance was set to 1.2mm and the moving speed of the head was set to 25 mm/s. The input printing model can control the two materials to be alternately stacked in the printing process. Performing model prediction according to a designed target 4D color change result, and setting the output microwave power of a microwave field generating device (a microwave solid-state source 1 and a rotary antenna coating rod 3) to be 180W according to input parameters of a prediction model; the temperature of the control unit 13 is set to 90 deg.c. The temperature of the material is controlled by the control unit 13 to stably float within the range of 90 +/-3 ℃ during the printing process. Because the color-changing wheat dough layer contains the color-changing powder sensitive to microwaves, the color-changing powder is damaged to release pigments under the microwave field treatment, so that the color of the color-changing wheat dough layer spontaneously changes layer by layer within 2min layer by layer along with the printing process in the printing process. The printer can realize the color change of the delta E value (compared with the color difference value of the original sample) within the range of 1.80-9.79. The final color change precision can reach more than 95% of the predicted value of the model. The color-changing area in the printed object can be regulated and controlled by a printing model established in advance, and controllable 4D real-time spontaneous color changing is realized.

Example 3: self-fragrance-emitting 4D printing method for fruit and vegetable dough

Mixing edible soybean oil and flavor oil according to a ratio of 4: 1, uniformly mixing to prepare the diluted flavor oil. 1% gum arabic aqueous solution, 1% gelatin aqueous solution and diluted pigment oil were mixed in a 50: 50: 1, and dispersing at 3000 rpm for 3 min. After dispersing evenly, adjusting the pH value to 4 by using 1% acetic acid aqueous solution, and then stirring at constant speed for 30min in a water area at 4 ℃. Standing after stirring, and layering. Taking down the precipitate, and freeze-drying at-80 deg.C under 220Pa for 20 hr to obtain fragrant powder.

Mixing fruit and vegetable powder, wheat flour and water according to the weight ratio of 1: 25: 10 are mixed evenly to prepare the wheat dough layer material which is filled into a charging barrel A14. Mixing fruit and vegetable powder, wheat flour and water according to the weight ratio of 1: 25: 10, mixing uniformly, adding 1% of flavor-changing powder (w/w), uniformly preparing into a flavor-changing wheat dough layer material, and filling into a charging barrel B15. Selecting a microwave shielding printing nozzle 6 of a charging barrel A14 with the diameter of 1.5 mm; the diameter of the microwave shielding print head 6 of the cartridge B15 was selected to be 1.5 mm. The printing distance was set to 1.5mm and the moving speed of the head was set to 30 mm/s. The input printing model can control the two materials to be alternately stacked in the printing process. Performing model input prediction according to a designed target 4D color change result, and setting the output microwave power of a microwave field generating device (a microwave solid-state source 1 and a rotary antenna coating rod 3) to be 140W according to prediction model parameters; the temperature of the control unit 13 was set to 70 ℃. The temperature of the material is controlled by the control unit 13 to be stabilized in a range of 70 +/-3 ℃ during the printing process. Because the flavor-changed wheat dough layer contains the flavor-changed powder sensitive to microwaves, the flavor-changed powder is damaged to release flavor oil under the microwave field treatment, so that the flavor release occurs layer by layer within 3min layer by layer along with the printing process during the printing process of the flavor-changed wheat dough layer. The printer can realize spontaneous release of target flavor substances by the flavor-changing layer, and the percentage of the released flavor substances in the total flavor substances can reach 33.79-35.51% through GC-MS detection. Compared with the aroma variation degree obtained by a prediction model, the aroma variation precision can reach more than 95%. The odor-changing area in the printed object can be regulated and controlled by a printing model established in advance, and controllable spontaneous 4D fragrance change is realized.

Claims

1. The application of the microwave-induced 4D printer is characterized in that the 4D printer comprises a printing Cartesian coordinate driving unit, a material extruding unit, a microwave field output unit, a microwave field leakage-preventing unit and a control unit (13); the material extrusion unit comprises a charging barrel, a charging barrel microwave shielding sleeve (7) and a microwave shielding printing nozzle (6); the microwave field output unit comprises a microwave solid source (1) and a rotary antenna coating rod (3); the microwave field leakage prevention unit comprises a fixed microwave shielding cover (4), an X-axis movable microwave shielding cover (8) and a Z-axis movable microwave shielding cover (5); the control unit (13) comprises a microwave output power controller, a temperature measuring device and a temperature controller;

utilize the 4D printer carry out 4D to food material and print, specifically include:

(1) selecting proper printing parameters and the diameter of the microwave shielding printing nozzle (6) according to the rheological property and the type of the material to be printed;

(2) setting the microwave output power and induced spontaneous change processing time of the microwave field output unit;

(3) and 4D printing is carried out on the material to be printed according to the printing model.

2. Use of a microwave-induced 4D printer according to claim 1, characterized in that in the material extrusion unit, the cartridge microwave shielding sleeve (7) is a hollow 304 stainless steel structure, into which the cartridge can be placed and shielded from the microwave field; the microwave shielding printing spray head (6) is in a 304 stainless steel structure, can be connected with the charging barrel through a screw, and has selectable nozzle diameters of phi 0.8, 1.2 and 1.5 mm.

3. The application of the microwave-induced 4D printer according to claim 1, wherein the microwave field output unit is disposed outside the 4D printer; wherein, the power supply power of the microwave solid source (1) is 500VA, 220V/50Hz, the output frequency is 2450MHz, and the continuous linear adjustability of the power of 20-200W can be realized; the rotary antenna coating rod (3) is a microwave output device and is positioned on the side surface of the fixed microwave shielding case (4) to ensure that a stable and uniform microwave field is provided for the microwave shielding bin where the printed object is positioned, and the microwave energy generated by the microwave solid state source (1) is transmitted to the rotary antenna coating rod (3) through the coaxial cable (16).

4. The application of the 4D printer utilizing microwave induction as claimed in claim 1, wherein the microwave field leakage preventing unit is made of 304 stainless steel, wherein the fixed microwave shielding case (4) is fixed on the 4D printer base; the Z-axis movable microwave shielding cover (5) is fixed on an X-axis movable sliding rod (11) of the 4D printer and can move along with the X-axis movable sliding rod (11); the X-axis movable microwave shielding cover (8) is fixed on a material extrusion unit sliding block (10) and can move along the X axis with the material extrusion unit; a flow-resistant microwave leakage-proof structure is adopted among different shielding cases,<1mw/cm²and the influence of microwave leakage on other units and the damage to operators are avoided.

5. The application of the microwave-induced 4D printer as claimed in claim 1, wherein the microwave output power controller in the control unit (13) can achieve the microwave output power of 20-200W continuously, linearly and precisely adjustable; the temperature measuring device (17) adopts an infrared online temperature measuring sensor, can display the temperature of the printed workpiece in real time, and has a temperature measuring range of 0-500 ℃; the control unit (13) is connected with the temperature measuring device (17) and the microwave solid-state source (1), and can realize the regulation and control of the microwave output of the microwave solid-state source within the control range of temperature.

6. The application of the microwave-induced 4D printer is characterized in that a microwave-induced spontaneous deformation, color change and aroma change prediction model is established in the process of 4D printing of food materials, and specifically comprises the following steps:

(1) temperature model of printed article in microwave field: calculating the temperature of each layer of the printed object in the microwave field according to an electromagnetic wave equation and a heat conduction equation, and calculating the value of the temperature T according to the following formula:

wherein, P is the power received by the printed object in the microwave field; epsilon₀Is the relative dielectric constant of electromagnetic waves in vacuum; ε' is the dielectric loss factor of the printed material; e is the electric field strength; omega is angular frequency; ρ is the print density, c_pIs the specific heat capacity of the printed material; t is the temperature of the printed object; t is time; k is the thermal conductivity of the printing material; f is the frequency of the microwave generated by the microwave source;

(2) deformation model: adopting a Matlab tool and calling a BP neural network module to establish a three-layer BP neural network model; setting algorithm parameters: the number of hidden layers is 10, and the training method is Levenberg-Marquardt; setting the input layer as (1) solving the derived object temperature and microwave heating time; the output layer is of a deformation bending angle; inputting the selected training sample into a BP neural network, training the BP neural network, comparing the output value of the BP neural network with an actually measured value until the mean square error of the BP neural network training meets the requirement, and determining the weight and the threshold of each layer of the BP neural network;

(3) color change model: adopting a Matlab tool and calling a BP neural network module to establish a three-layer BP neural network model; setting algorithm parameters: the number of hidden layers is 10, and the training method is Levenberg-Marquardt; setting the input layer as (1) solving the derived object temperature and microwave heating time; the output layer is a Lab color difference value compared with the original color; inputting the selected training sample into a BP neural network, training the BP neural network, comparing the output value of the BP neural network with an actually measured value until the mean square error of the BP neural network training meets the requirement, and determining the weight and the threshold of each layer of the BP neural network;

(4) fragrant change model: adopting Matlab language to program, and calling a BP neural network module to establish a three-layer BP neural network model; setting algorithm parameters: the number of hidden layers is 10, and the training method is Levenberg-Marquardt; setting the input layer as (1) solving the derived object temperature and microwave heating time; the output layer is the signal value of the target flavor substance measured by GC-MS; inputting the selected training sample into a BP neural network, training the BP neural network, comparing the output value of the BP neural network with an actually measured value until the mean square error of the BP neural network training meets the requirement, and determining the weight and the threshold value of each layer of the BP neural network.