Current State of Applying Smart Materials in Consumer Durables: A Literature Survey

Current State of Applying Smart Materials in Consumer Durables: A

Literature Survey

Azrol Kassim

_{, Imre Horváth}

_{and Bart Gerritsen}

1_{Faculty of Industrial Design, Delft University of Technology, the Netherlands} 2_{Faculty of Design and Architecture, Universiti Putra Malaysia}

a_{A.Binkassim@tudelf.nl,} b_{I.Horvath@tudelf.nl,} c_{B.H.M.Gerritsen@tudelft.nl}

Keywords: Smart materials, consumer durables, applications, product design

Abstract. Smart materials have drawn substantial attention and interest in a broad range of

applications, due to their unique and superior characteristics. However there is a blurry image over the potential applications of smart materials in consumer durables. This has stalled further research and decision making in initiating the development of consumer durables based on smart material technologies. This literature survey investigates the applications of smart materials in consumer durables in a retrospective manner. It formulates a conceptual foundation for exploring potential application areas and opportunities. In this paper, publications revealing to the applications of smart materials are structurally reviewed. The publications have been categorized based on seven classes of smart materials. The analysis revealed the frequency distribution of the publications based on the reported application of smart materials in ten consumer durable categories. The results show that shape changing smart material is the most frequently used and widely distributed class of smart material. Moreover the publications informed us that the knowledge on shape changing smart materials are more ‘readily accessible’ then that on other classes of smart material. Nonetheless, shape changing smart materials applications in consumer durables are still limited. On the basis of our main findings we discussed about the new opportunities and directions for future research and application in consumer durables. As conclusion to this research, cross-disciplinary research between the domain of material engineering and product design were proposed in order to improve the situation. Furthermore it could be done through dedicated methods and software tools, which allows the exploration of relationship between the requirements of specific applications regarding the characteristics of shape changing smart materials.

Introduction

Over the past decades, advancements in the domain of engineering materials have been spectacular. This is certainly true for nano-infused materials, bio-engineering materials, smart materials, and combinations of such materials. Various favorable societal and technological conditions have contributed to these rapid developments: at a societal level, the perceived need to transfer from a fossil-based into a bio-based society has sparked massive research programs that start to deliver a wide range of bio-based engineering materials. Nano-sciences have delivered technologies allowing the manipulation of materials at molecular and atomic scales in industrial processes. This led material manufacturers to explore the design and manufacturing of engineering materials of which properties can be manipulated and controlled within tiny conditional envelopes, in response to external stimuli. By removing, controlling, or installing these stimuli, the material behavior can be controlled, typically to a much wider extent compared to traditional materials. In their design of smart materials, material engineers seek to provide materials with clearly distinct controlled behavioral states. For instance, by providing a stimulus, a shape changing smart material can thus flip from a state of high stiffness into a state of reduced stiffness, or from a state of high deformation into a state of zero-deformation, effectively retaking a preferred shape.

In this paper, smart materials can appropriately be defined as ‘purposely designed’ engineering materials, which in response to one or more predefined stimuli, can be brought from one controlled

conditional and behavioral state into a next, in a controlled manner, and which do not flip states otherwise. Examples of smart materials are: shape memory alloys (SMA), piezoelectric ceramics, photovoltaic cells and thermo-chromic ink. Contemporary applications of smart materials include sensors, actuators and transducers in the first place. Their programmable behavioral state or ‘smartness’ is immediately linked to the functionality of the sensor, actuator or transducer, in similar vein with the link between the classical bi-metal strip material behavior and its function. Further applications of smart materials have been reported from the domains of aerospace [1], robotics [2], and medical [3].

Despite their prospective opportunities and meaning for the development of consumer durables, the application of smart materials by product designers, has been daunting [4]. We had to come to the conclusion that the studied literature does not outline the root-causes of this phenomenon. However there is some consensus that additional streams of knowledge are needed to convey the details of applying smart materials to product designers. Explorative and orienting discussions with experts in the field revealed that knowledge transfer is necessary, but additional factors have to be considered. For instance additional epistemological, business, technological and methodological issues seem to play a role too.

The scientific treatises on smart materials are primarily written by material scientists, who have a differing background from product designers. Their epistemological approach, structuring and reasoning differs significantly from that of product designers [5]. We assume that this as an epistemological barrier. Secondly, material knowledge may be of strategic importance to materials manufacturers, giving them a unique market position; this is a strategic business barrier. Thirdly, there is the technological barrier: in a product design context, many aspects play a role that cannot be considered and weighted solely by material engineers. Finally, methodological issues are also influential, as smart materials require a different form of design decision making, based on different types of design knowledge, and typically at a much earlier stage in the product design process compared to conventional materials. In the analysis of our research problem and our research approach, we wish to explore these additional factors.

However, we also realized that different classes of smart materials may pose different application issues to the product application [6]. As the applications of smart materials are present in many consumer durables categories, a careful assessment of the phenomena needs to be done from an operative level. Therefore, it is necessary to know the state-of-the-art of the domain. The aim of this contribution is therefore to present a systematic review of the publications from the literature covering the applications of various classes of smart materials in consumer durables.

In this paper, we performed a systematic assessment on the publications regarding to the applications of smart materials in consumer durables. The publications were organized in a compliance matrix based on their fitting classes of smart material and to the applications of consumer durable category they belonged to. Based on the compliance matrix, we analyzed the frequency distribution of the publications. For our discussions we explicate the findings towards suggesting the most prominent areas for future research in the applications of smart materials. As a conclusion to this paper, we formulate propositions for future research.

The paper is organized as follows. Section 1 introduces our approaches to systematically asses the literatures. Here we reveal the classes of smart materials and identify the different categories of consumer durables. Next in section 2, we introduce the methods that were used in this literature survey. In section 3, we present the results of the literature survey. Section 4 is dedicated to discuss the findings. Finally in section 5, we proposed recommendations for future research.

Systematic Approach to Reviewing Applications of Smart Materials

Research in smart materials has robustly stimulated both the academia and the industries to develop improved material compositions and functionality, to explore potential applications possible for these novel materials. However the knowledge on how to apply smart materials is still slowly disseminating especially in the research and development of new products [7]. In the product design practice, we assume that designers have less awareness and knowledge on smart materials. The mainstream material selection and evaluation tools, conventional methodologies or textbooks used by product designers hardly mentioned about the properties and behavior of smart materials. Furthermore, the knowledge on smart materials is not easily available for direct usage in their design practices and restrictedly accessible for product designers. As a strategy for product design to successfully enter the domain of smart materials, there is a need to identify the root causes of the phenomenon. However it is also not easy because there are considerable types and various classes of smart materials that have been developed by material engineers. Each of them may own to unique properties and specific application requirements. As a starting point, we proposed to manage the complexities of the phenomenon by reviewing different classes of smart materials. Existing classifications of smart materials classification can serve as a quick starting point to support this literature survey and the review of the publications.

Several works had been done in the past to classify smart materials from the design perspective. The studies intended to identify the most useful and advantageous characteristics of smart materials, which could inspire the generation and embodiment of ideas for designing products. Generally, smart materials have been classified based on the principle of responses to stimuli, for instance light, electricity or magnetism [8]. Other scholars have also proposed smart material classification based on function similarities, where specific changes on materials can be physically observed or sensed. Further on the classification sorts smart materials into three main classes which are (1) property changing (consisting of color and optical changing, adhesion changing, and shape changing), (2) energy exchanging: (consisting of light emitting and energy generating, energy exchanging and (3) matter exchanging [4] and [9]. For this literature survey, we were inspired by the latter classification scheme. However we decided to disregard the use of the three main classes of smart materials. Instead, we suggest classifying smart materials into seven classes which are presented in the following Table 1. The proposed classification of smart materials enables us to discover various keywords which will be used to search the academic databases for relevant publications. These keywords were referred from several leading literatures in the smart material domain, for instance [4], [8] and [9]. The keywords used for searching on the various smart material classes are also presented in Table 1. Having a repository that links smart materials to its consumer durables application can only be effective if the contents are relevant to the intended product designers. There needs to be a fundamental parameter which will enable better communication and reference to discuss whether existing contents are relevant. For example, product designers are rarely involved, for instance, in the design of microprocessor or detergent. Typical products designed by product designers which are (a) tangible, (b) man-made, (c) series or mass-produced, (d) made predominantly for consumers and (e) durable [10]. Subsequently inspired by this reasoning, we sort that in general product designers have been extensively involved and contributing significantly in the development of consumer durables in ten categories. We investigated the applications of smart materials in ten consumer durables categories namely: consumer electronics (CE), automotive (AU), medical and healthcare (MH), household appliances (HA), household hardware (HA), wearable apparel (WA), furniture (FU), toys (TY), sports and recreation (SR), and packaging (PC)

Method of Literature Survey

This survey research has been done to the research publications concerning to the applications of smart materials in consumer durables. The method has been to screen the publications in search of papers mentioning the potential applications, experimentation, or utilization of smart materials in relevance to the selected categories of consumer durables. In this review process, a large number of papers were excluded because they do not belong to the categories of consumer durables. For instance we did not look into the publications belonging to robotics, industrial machinery and aerospace. As a result to the publication screening method, only 220 publications were selected for this survey. Figure 1 shows the number of publications that were selected concerning the seven classes of smart materials.

Table 1. Classes of smart materials, their definition, and keywords used in database search

Smart material class Definition Keywords used

Color or optical changing (COC)

Materials that change their color and/or optical properties in response to certain stimuli

Photochromic, thermochromic, mechnochromic, electrochromic, chemochromic

Electricity generating (EG)

Materials that produce electric current after contact with stimuli

Photoelectric, thermoelectric, Piezoelectric, chemoelectric, photovoltaic

Energy-exchanging (EE)

Materials that are capable of transforming, storing and releasing energy from one state to another upon contact with stimuli

Hydrogen storing, phase change, paraffin, heat storing, light storing, electricity storing

Shape changing (SC) materials that have the capability to change shapes and recover after stimulated

Shape memory alloy (SMA), shape memory polymer (SMP), shape memory composite, electroactive polymer, thermobimetals

Light emitting (LE) Material that converts input energy to radiation energy in the visible spectrum after stimulated

Photoluminescent, electroluminescent, bioluminescent, hemoluminescent, crystalloluminescent, radioluminescent, radiophotoluminescent, triboluminescent Matter-exchanging (ME)

Materials are able to reversibly take up and/ or in, to bind and release matter either in the form of molecules, gas, liquid or solid components by various physical or chemical processes

Particle, gas, water storing

Adhesion changing (AC)

Materials that changes the attraction forces of adsorption or absorption of atoms or molecules of solid, liquid or gaseous components after stimulated

Bioadhesive, hydroadhesive, electroadhesive, themoadhesive, photoadhesive

Figure 1 Number of publications selected concerning the classes of smart materials

0 20 40 60 80 100 120 COC EG EE SC LE ME AC

The selected publications were later organized in a compliance matrix based on the classes of smart materials and the consumer durable categories they referred to. The compliance matrix enabled us to analyzed the frequency distribution of the publications, and identify thought-provoking areas where comprehensive review on the publications is needed. By analyzing the distribution of frequency of occurrence, we identified the most important class of smart materials based on the compliance matrix. Furthermore, we perceived the dominant consumer durable categories that were covered by the smart materials.

Current State of the Publications

Results of the compliance matrix

We present the result of organizing the publications in the compliance matrix in table 2. In order to support the analyses of the result, we converted the frequency of publications in percentage. We observed that almost half or 49.9% of the publications are covered by SC smart materials. This is followed by COC (17.7%), EG (16.8%), in LE (7.2%), EE (6.8%), ME (1.36%) and AC (0.9%). The situation of application differs among the 7 classes of smart materials. Based on the results, three classes of smart materials which are SC, COC and EG were of distinctive interest for further review in this paper. As we found out from the compliance matrix, the three classes of smart materials were well presented in the sample of publication. Moreover, the range of applications extends to more consumer durable categories in comparison with the other classes of smart materials.

Review on important applications of smart materials

Concerning shape changing smart materials, applications were observed covering all 10 consumer durable categories, particularly in CE, MH, WA, and AU. A substantial number of publications have also mentioned other consumer durable categories. An in depth review on literature suggest that the most important applications of SC smart materials includes actuators, sensors and deploying structures. In WA, SC smart materials were used in electronic textile, smart-comfort garments, and shape-memory sportswear [11] and [12]. In MH, applications includes stent graft, biopsy forceps, and medical patch sensors [13], [14], [15] and [16]. In general, these functionalities of SC smart materials were used for the purposes of energy saving, recycling and safety features in the applications. In terms of COC smart materials, applications were found centering in AU and HA. Thermochromic and electrochromic materials are primarily applied for energy saving function in smart glazing window and as sensors [17], [18] and [19]. A limited number of publications were also observed in CE, WA and PK. In regards to EG smart materials, applications were reported mainly in CE, HH, HA and AU. Here, photovoltaic and piezoelectric materials have been important in the control of temperature and generating electrical power [20] and [21].

A number of SC, COC and EG based smart materials have already been available for the market, thus contributing in better access to the technology, for researchers and the industries. Some examples of commercialized smart materials in SC, COC and EG that were found in literature are presented in Table 5. These smart materials are produced for the uptake of the consumer durables developers. Differently, there are other cases where companies are involved in the co-development of smart materials and their consumer durables application. For example, He et al. reported the applications

Table 2. The frequency distribution of publications in a compliance COC EG EE AC LE ME SC CE 3 22 0 0 4 3 50 AU 21 7 1 0 0 0 15 WA 4 0 10 0 12 0 21 HH 0 12 5 0 2 1 8 MH 0 2 0 2 2 0 26 HA 8 7 3 0 1 0 8 TY 0 0 0 0 0 0 1 PK 3 0 0 0 0 0 2 SR 0 1 0 0 0 0 1 FU 0 0 0 0 0 0 2

of SMP for snap-fits in Nokia mobile phones [22], while Hayashi et al., reported their SMP applications within Mitsubishi Heavy Industries Ltd. [23]. To induce, publications have suggested that co-developments have been driving the applications of shape changing smart materials in consumer durables.

Table 2 Example of commercialized smart materials in literature

Discussion

Findings based on studying the literature

Based on this systematic investigation, it can be stated that in general the publications concerning the applications of smart materials is still limited and scarcely available. The survey demonstrates that the applications of smart materials have been explored in many consumer durable categories. However, the extent of applications was different in each class of smart materials. We did not found any underpinning theory that explains why a number of consumer durables are more supported by smart materials while not in the others. Nevertheless, there are indicators suggesting that specific application situations may pose special requirements on smart materials [36]. Obviously, the solutions for spreading the applications of smart materials cannot be expected without an explicit study in each class of smart materials.

There has been very limited number of publications concerning the LE, EE, ME and AC classes of smart materials. This indicates that the fundamental understanding on these classes of smart materials is still superficial. In case of many consumer durables, we are still expecting for realistic and commercialized applications of smart materials. Nevertheless, literatures have revealed that the applications of smart materials is still limited because of several disadvantages which includes their higher cost for production, limitations in material behavior and properties, or restrictions on environmental and manufacturability [36], [38] and [39]. Furthermore, there are also other disadvantages associated to the restriction of function and use of smart materials for fitting specific product requirements [4], and [40]. For the time being, fundamental research on various classes of smart materials have been attempting to deal with the technical disadvantages [41] and [42]. Apparently there is not enough information such as material properties, material stability and cost of applying, which prevents product designers from increasing their awareness and knowledge on most of the classes of smart materials.

SC is currently the most dominant class of smart materials applied in consumer durables. The result of the survey shows that half of the publications studied SC smart materials. On the other hand this relatively high number of publications indicates that there is a significant interest in SC smart materials and it can be expected that they will grow into mature technologies. This state of matureness can lend itself to a more extensive application in various consumer durables categories. In order to support the applications of the shape changing smart materials, several approaches have been proposed by researchers including application strategies, material selection methods and simulation

Smart material class Type and

commercial name of SM

Company References

SC

COC

EG

technologies [43] and [27]. Hu et al. for instance proposed a strategy for the applications of SMP study in textile products [6]. Meanwhile Huang outlined the parameters for selecting SMA for designing actuators [44]. On the contrary, reports on these approaches were seen very less available in the publications of other smart material class. This observation suggest that there are sufficient knowledge available in shape changing compared to other classes of smart material. However, since we did not take into account other sources such as books, patents and website in the survey, we could not confirmed our claim. Nevertheless, the publications used in this survey may have at least point out otherwise.

In our survey, we discovered that the applications of shape changing smart materials extents to all categories of consumer durables, in particular to CE, AU, WA, and MH. Early applications have shown that shape changing smart materials offers the opportunity of achieving higher functional utility and economic value [45]. Nevertheless, further efforts are to be made to study the success factors of previous applications and transfer this knowledge to new application areas [11]. It is still unclear which factors are the strongest enablers or obstacles of application of SC smart materials in various categories of consumer durables. The relationships amongst the functional, technical, environmental, economic, and manufacturing factors should be better understood before broadening the range of applications.

The majority of publications concerning SCSM have been published in material engineering journals. The publications were found in material engineering journals such as Materials Design, Polymers, Materials Letter and, Science and Technology of Advance Materials. Hence, the publications are expected to provide information from the material engineering’s point of view. Publications from material engineering are believe to be less attractive and not easily transferable to the product design domain [4]. The experiments from the material engineering publications reveal empirical results by using technical terms, which are often difficult to be perceived by product designers [46]. Hence, the product design domain could not react accordingly to the information prepared by material engineers [47].

On the contrary there were only a limited number of publications that address product design issues. This fact entails that product design aspects and requirements have yet not been addressed sufficiently in the literature. In order to improve the involvement of product design in smart materials research, it seems to be necessary to conduct cross-disciplinary research in order to extend the current one sided, materials engineering view on the applications of SC smart materials with specific design knowledge that facilitates their use in consumer durables. In fact, cross-disciplinary research between the two fields have been suggested in material engineering publications such as [6] and [48]. In addition to that new methods and tools are also needed to make designing with SCSM a creative and productive daily practice in the near future.

Key recommendations from the literature survey

From the literature review, the following propositions are proposed for future studies. They concern both academia and industry. The recommendation shall support the link between fundamental research in material engineering and application research in product design engineering. The future perspective should be valuable for industry, as many organizations are still struggling to commercialize their smart materials. For academia, the recommendations can be used to develop novel research to improve the applications of smart materials in consumer durables. The following propositions are therefore proposed:

1. As a first step we proposed to elaborate a holistic reasoning model (including both theoretical and methodological) for application of SCSMs.

2. A holistic approach is needed, which combines the knowledge and methodologies of material engineering and product design in the above context based on cross-disciplinary abstractions. 3. The relationship (the interplays and complexities) between the requirements of specific

4. In order to be able to apply SCSM creatively and successfully in consumer durables, the integral knowledge from materials engineering and consumer durable design should be embedded in dedicated methods and software tools.

Conclusions

The aim of this study was to provide an overview of the current status of the applications of smart material in consumer durables. For this goal, it was necessary to make a systematic study on the literatures covering this domain of interest. The survey covered a representation of publications from 7 classes of smart materials. We reviewed the frequency distribution of the smart materials in 10 consumer durable categories. We have proposed 4 propositions for future research uptake, hence to improve the applications of smart materials in consumer durable design.

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