Design And Research Of Intelligent Tamper-evident Packaging Materials Based On Printing Electronic Technology

The greenization and security issues of packaging industry have always been social concern topics and hot points in academic research.Judging from the development process of packaging industry at home and abroad,the research of packaging industry in the fields of security and intelligence has still been in the exploration and initial stage.Along with the development of society and technology,printed electronics(PE)technology has gradually attracted the attention form packaging researchers all over the world.The trait of PE is fabricating electronic components or sensors on flexible substrates in large quantity by printing method so that it can overcome the shortcomings of traditional silicon-based electronic products(such as high price,poor rigidity,high pollution and etc.)Because of that,PE has great application potential in many fields.Ag nanowire(Ag NW),as one of metal nanomaterials with excellent flexibility and conductive performance,is an important component in the preparation of conductive inks in PE.From the discovery of experiment,the V-shaped Ag NWs have better electrical properties than linear Ag NWs so that they are seemed to have broad application prospect in PE technology.Therefore,V-shaped Ag NWs are selected as a main research target in this project,and the controllable preparation methods,growing mechanism and application of V-shaped Ag NWs are studied.As for printing technology,screen printing is used in this project,which has some advantages of simple operation,low cost,and large-volume reproduction.It can be used to prepare patterned Ag NWs flexible electrodes and flexible sensors.Intelligent packaging is a new packaging type by combining intelligent technologies with packaging application.The tamper-evident packaging is one of the security packaging types which belong to intelligent packaging.And the tamper-evident packaging can be applied to many product packaging fields,such as precious products,high range goods,secret files,etc.Existing present tamper-evident packaging usually adopts special structure or digital password to achieve the function of tamper-evident,which is generally not intelligent.However,PE offers technical supports and possibilities to design and manufacture of intelligent tamper-evident packaging.The conductive ink can be transformed to flexible substrate to fabricate flexible sensors by PE technology.And the sensors can also be applied to the opening parts of packaging to manufacture the intelligent tamper-evident packaging.In this paper,the controllable preparation method and growing mechanism of Vshaped Ag NWs are studied.Then,Ag NWs with excellent properties are prepared and used to fabricate high-performance conductive ink.After that,the conductive ink is printed onto flexible substrates to prepare flexible electrodes and sensors.Finally,the intelligent tamper-evident packaging is manufactured by combine flexible sensor and packaging.The research contents and innovations in this paper mainly include the following four parts:(1)V-shaped Ag NWs are prepared by polyol method.And the effects of additives,concentration of additives,reaction temperature,oxygen content,centrifugal treatment,ultrasonic treatment to the morphology and structure of V-shaped Ag NWs are studied.More importantly,the growing mechanism of V-shaped Ag NWs is proposed.The results of experiments show that Ag NWs with good quality can be prepared using CuCl2(2.22mM/L)at 160 ?.And the less oxygen,the higher quality of Ag NWs products.The type of centrifugal agent has no effect on the morphology of Ag NWs.Moreover,the larger centrifugal speed,the shorter the length of obtained Ag NWs.Studies have found that ultrasonic treatment is the dominant factor that leads to the growth of Ag NWs from "linear" to "V-shaped",and the growing mechanism of Vshaped Ag NWs is proposed: linear Ag NWs break under the ultrasonic treatment with new(111)crystal surface formed on the cross-section,and atomic channels are formed after the new crystal planes contact each other.Then two linear Ag NWs grow into one V-shaped Ag NW by cold welding.(2)The water-based conductive ink is prepared with absolute ethanol and deionized water as solvent,PVP as binder and V-shaped Ag NWs as conductive filler.In this paper,the viscoelasticity and thixotropy of the ink are tested.The printability of conductive ink on the surfaces of PET,paper and textile are also tested.The conductivity of the ink is tested with different sintering time and sintering temperature.The testing results show that the rheological property of the conductive ink is suitable for screen printing.What's more,the average contact angles of the ink on PET,paper and textile are 39.34°,45.30° and 65.48°,respectively.And the printing products also have flat printing surfaces and clear edges,which indicates that the ink has good wettability and printability on these three substrates.After sintering at low temperature,the printed flexible electrode has good conductivity and stability,and can make the LED lamp emit light stably in both flat and bending states.(3)Flexible sensors with different patterns are fabricated by screen printing method.The influence of printed pattern shape,width and bending angle to the electrical performance of sensor is studied.The mechanical stability and change mechanism of sensing performance of the flexible sensor is tested.The experimental results indicate that the linear type sensor with 2 mm line width has the best performance.Pre-bending treatment makes micro-cracks appear in the bend area of sensor,and micro-cracks promote a stable rule of the resistance change of the sensor during bending cycles.Based on this,a preparing method of flexible bending sensor with high sensitivity and stability is proposed to meet the needs of packaging application.(4)The motion states of flexible sensors "from straight to bend" and "from bend to straight" are consistent with the two movement states of the box(opening and closing).And two types of intelligent tamper-evident packaging are designed by combine the flexible sensors and the swing cover of the packaging: the swing cover type intelligent tamper-evident packaging(including airplane box and hinge cover intelligent tamper-evident packaging)and intelligent peel-off tamper-evident packaging.In order to verify the performance of tamper-evident packaging,resistance changing signals of sensors are collected during the opening process of two types tamper-evident packaging.The results demonstrate that the airplane box with sensor can steadily monitor the signals when the shaking cover is opened at 90°.The hinge cover tamper-evident packaging can steadily monitor the signals when the packaging cover is opened at 45°,90°,and 135°,respectively.And the peel-off type packaging can also monitor the signal when the PET-based flexible sensor on the packaging is peeled off.Finally,we summarize and analyze the work mode and application of intelligent tamper-evident packaging,and we propose the application prospect of intelligent tamper-evident packaging in the field of cultural relics packaging and related fields.