Organic interfaces

Proceedings of TMCE 2014, May 19-23, 2014, Budapest, Hungary, Edited by I. Horváth, Z. Rusák  Organizing Committee of TMCE 2014, ISBN 978-94-6186-177-1

ORGANIC INTERFACES

Wim Poelman

Fac. of Industrial Design Engineering Delft University of Technology

w.a.poelman@tudelft.nl Erik Tempelman Fac. of Industrial Design Engineering

Delft University of Technology e.tempelman@tudelft.nl

ABSTRACT

This paper deals with the consequences for product designers resulting from the replacement of traditional interfaces by responsive materials. Part 1 presents a theoretical framework regarding a new paradigm for man-machine interfacing. Part 2 provides an analysis of the opportunities offered by new materials technology for interaction styles. Part 3 discusses the consequences regarding design practice. Conclusion is that the design of product semantics based upon change of colour, form, texture, etcetera, will become an essential aspect of product development.

KEYWORDS

Semantics, smart materials, organic interfaces, man-machine interaction

1. INTRODUCTION

The title of this paper introduces the concept of ‘Organic Interfaces’. The word ‘Organic’ is used in different contexts, e.g. organic food, organic growth and organic forms [12]. With respect to this paper, ‘organic’ relates to “forms, methods and patterns found in living systems” (WIKI). Traditional product interfaces do not occur in nature and the reason is clear. They are not necessary. The richness in nature for interfacing is enormous. Just look at how flowers communicate with the world through physical expression, colour, sound and smell. For man-made artefacts, technology did not offer too many affordable potentialities until recently. Therefore, product interfaces relied on limited media, such as beeps, blinking LED’s, text displays and ‘on-off’ input media such as buttons and (more recently) touch-screens.

Because of the limited media, it was necessary to apply abstract semantics. There was no direct relation between the message and the way it was

communicated. A red blinking LED has no direct relation with the fact that something is wrong. We had to learn (often through inaccessible ‘user manuals’) to give this meaning to a red light in a certain context [13]. There are, however, many other ways of telling that a machine does not function properly. For instance, organic ways would rely on unusual sounds or intense vibrations. Or perhaps it would be possible that the part of a machine which causes trouble changes colour. All this options where not feasible based on traditional technology. However, modern responsive materials make it possible – and affordable. Now it is up to designers how to use this technology effectively. The importance of design of product communication will increase substantially because of the introduction of more responsive materials.

2. PART 1 THEORETICAL FRAMEWORK

2.1. Interaction styles

For every responsive material systems counts that there is an input, resulting in an output.

Input can be light, pressure, movement, heat, electrical power, chemical reaction, etc., possibly mediated by time. Output can be the same as input; in the context of man-machine interfacing, output only makes sense when it is observable by and understandable for the user. Output should be attuned to the senses of humans. Traditional categories of senses are tactility, sight, sound, taste and smell, but for human man-machine interface design, this classification is not very useful. Rather, the question should be 'what would we like or expect to perceive and how products could realize that perception'. Reflection on this question may lead to other forms of output, such as movement, shape change, vibration, colour change, changing reflection and texture, sounds, etc., again mediated by time

(consider: rapidly blinking lights versus softly pulsating glows).

In fact, these kinds of outputs are quite usual in existing products; however, they are seldom built in consciously by the designer. Some examples:

We recognise a flat tire by vibration, different feeling of the steering wheel, difference in movement and sound of the car and shape change of the tyre. However, we do not regard this as an interfacing issue, probably because of the fact that the output is not explicitly designed. It was not necessary to design it because the output was obvious.

Only rarely the questions are posed: what does a product communicate about its status itself? Does this provide enough information, or should the designer create extra output? For instance, we notice that a copier may not work properly, but because of the red signal we know it for sure.

It is not necessary for an adjustable chair to communicate its seat level by a display. You just see it.

You don't need a display to see that your vacuum cleaner is working. You just hear it is, and see the result on the floor.

Direct communication by a product to the user about its status can have many forms, and these forms are subject for design. The opportunities for giving form to status output have been spectacularly increased by modern materials, but still the actual solutions provided by designers are poor. The reason is probably that designers let themselves be limited by the existing components, such as LED’s, beepers and text displays.

2.2. The product IS the interface [13]

The view on man-machine interfaces is changing. In the past, interfaces were regarded as entities which were positioned between a product and a user. It could be physically attached to the product, but it could also be a stand-alone product (e.g. a remote control). Nowadays, gesture recognition makes it possible to operate products without any device at all. Interfaces have become immaterial. All you need

is cameras, microphones and a lot of software on a computer chip.

The question is if the design problem of interfaces is solved by just applying this technology. The answer is “no”. Instead, a new series of design problems is revealed by the enormous potential of technology and the spectacular growth of the amount of functions a product can take charge of.

In the past products mainly took over physical functions from the user. In this information era, mental functions are taken over as well. A product is not anymore defined by just design requirements, but also by a man-machine “contract” in which the rules for cooperation between them are recorded [1]. It is not anymore the user who operates a product through an interface, but a user and a product cooperating by perceiving each other and both deciding for action, based on the interpretation of the perceived information related to the goals of the cooperation.

Users and products will not relate to each other anymore as master and slave but as partners aiming for an objective, which is generally decided for by the user, or possibly even by the supplier of the device (an objective of the supplier could be to avoid law suits because of accidents).

Concluding, we argue that the relation man-machine is changing from a paradigm in which the interface is acting as an intermediary between user and device to a paradigm in which man and machine communicate directly.

2.3. Extension of human capabilities

Donald Schön [3] and others defined “extension of human capabilities” as a main goal of technology. Philosopher Peter-Paul Verbeek [2] added to that idea the principle that technology is not something that humans work with, but something that is part of being human. The technology used by humans is part of their being.

In fact there is nothing new about that. A pair of spectacles is an extension of your sense of sight. Your clothes are an extension of your capabilities to manage body temperature, as well as an extension of you capabilities to express yourself.

Already thousands of years, a horse was an extension of our capabilities to move. The difference between spectacles and clothes on the one hand and horses on the other hand is the fact that horses are smart

‘products’, perhaps the first we ever used. As the phenomenon of smart products is booming, it is time to learn from them.

2.4. A restricted analysis of horse riding

The question is whether a horse, as a ‘product’, has an interface. Of course we could regard the reins as an interface, but the reins only provide a control, regarding the principles of man-machine systems in figure 1, which is as well applicable to a man-horse system.

When we regard the horse as a product, we can discern several displays. The horse provides the rider with information about its status mainly by body language, movement and sound. The receptors we use to perceive the information of the horse are not just eyes and ears, but our whole body.

Experienced horse riders have a complete set of heuristics and automated responses to their disposal in their brains. They use their hands, buttocks and legs as effectors to provide the product/horse with instructions. Controls of the product/horse are mainly the mouth and the side, but also the neck for expressing satisfaction with its behaviour. It is impressive to see how sensible a horse is to extremely subtle inputs.

The product/horse processes this information and decides what to do. And here we see the most important difference compared to traditional man-machine systems. The horse can refuse to take action, or it can give its own interpretation to it.

So, a horse is a smart ‘product’ that does not obey its user slavishly. A horse refuses when an instruction leads to too much danger. But, in addition, a horse ‘feels’ the mood of the rider and takes this into account in its responses. Consciously or unconsciously, the horse may protect its user by deciding not to walk under a low hanging branch. It may be impossible to imitate all the expressive potential of a horse into a product. This is not the objective of this analogy. The purpose is to learn ourselves think differently about interfacing.

The analogy presents a new paradigm for interface design in which the purpose is not anymore that of controlling the artefact. Instead, the goal is optimising the cooperation between artefact and user.

Figure 2 Man machine system

Figure 3 Ankie van Grunsven

3. TECHNICAL OPPORTUNITIES FOR

THE NEW INTERACTION PARADIGM

3.1. Introduction

It is impossible to present a complete overview of technologies available to realize organic interfaces. However, the goal is to illustrate that there are many technologies which are based on a set of principles. These principles are based on three levels:

- New material systems on molecular level - New material systems on particle level - New material systems on structural level

Another classification which is of importance is if the responsiveness is combined with a sensing function.

3.2. Molecular level

Some responsive properties of materials are based on mechanisms on molecular level. In this paper the technologies will not be explained in detail, but some examples are presented briefly.

Shape memory metals are one of the oldest examples and some decennia’s ago also shape memory polymers were introduced. Both material types are

controlled by temperature. Shape memory metals are active. This means that they can be used as an actuator. Temperature makes them change shape. Shape memory polymers are good in keeping shape. At a defined temperature they can be deformed and after cooling they keep this form. Heating them up again brings the material in the original shape. An important group of responsive materials on the molecular level are piëzo electric materials. These materials produce an electric potential under pressure. The system is reversible. As a result of an electric potential it deforms. The material is widely applied in sensors, keyboards, microphones etcetera. Especially interesting are the Electro Active Polymers (EAP). They form a relatively new class of "smart material" that deform in the presence of an applied electric field, much like piëzo-electric actuators.

However, unlike piezoelectric actuators, EAPs operate on fundamentally different principals and produce force / strain / deflections more similar to that of biological muscles. There are two types: ionic and dielectric. The ionic EAPs operate through the movement of ions within a polymer, as shown in the diagram below.

They are essentially an elastomeric capacitor -- electrostatic forces cause charged electrodes to squish an intermediate polymer layer causing it to expand, as shown in the diagram below. The entire process is also reversible, which can be used to generate electricity or be used as a sensor (much like piëzo electrics). Dielectric EAP’s form the basis of the electro-active polymer artificial muscle (EPAM) "spring roll" actuators developed by SRI International.

Colour changing surfaces

Colour changing is possible based on e.g. reduction and oxidation of PEDOT:PSS/PAH films, that

Figure 5 Principle of Electro Active Polymers [5]

changes their light transmission and absorption values. Two polymers are used. A cathodically colouring polymer and an anodically colouring polymer, deposited onto transparent electrodes and separated by a electrolyte (PAMPS gel) to allow ion transport. The anodically colouring polymer appears transmissive in its neutral state. Upon oxidation it colours absorbing light in the visible region. The cathodically colouring polymer is coloured in its neutral state, becoming transmissive upon oxidation. When both polymers are combined together in several multilayers and a voltage is applied, the device switches between a coloured state and a transmissive state.

3.3. Responsive materials on particle

level

Many responsive materials function on particle level. Particles are added to elastomers to realize certain functions, such as changing colour or elasticity. A very interesting one is adding magnetic FE powder to an elastic foil [7]. As soon as the material is placed in a magnetic field the foil contracts and stiffens. This technology can be applied for speaker systems or interfaces. A keyboard could just be a foil. Parts of the keyboard could be blocked off if necessary. [6] The latest development is the addition of nanotubes with about the same objective.

Even more functionality is provided with piëzo powder in polymers. The result is a piëzo system that, different from piëzo elements is free in its form and flexible. In principle a whole product can be sensitive, because piëzo systems provide electrical signal under pressure. One of the alternatives is

adding piëzo particles to paint. Piëzo electric paint can be used for many applications

3.4. Responsive materials on system

level

The most interesting applications are developed on system level. Three of these applications are explained below.

Adaptive Building Components

A researcher in Delft, Charlotte Lelieveld [8] developed a material system based upon a combination of shape memory Alloy (SMA) and shape memory polymer (SMP). The SMA is embedded in the SMP sheet, as well as heating wires. When the system is heated, the SMM changes form, as well as the flexible SMP.

As soon as the SMP is cooled it freezes the form. The goal of the research is to realize functional changing surfaces in architecture.

Figure 7 Demonstrator with lifting mechanism made of elastomer foil

Figure 8 Electric Activation of the smart composite

Electronic Origami with the Color-Changing Function [15]

Tatsuya Kaiho and Akira Wakita experiment with the possibilities of a foldable, paper like, colour – changing material, so-called “electronic origami. The principle is the combination of thermo chromatic material at the one side and conductive ink at the other side.

Figure 10 Structure of color-changing Origami paper

The conductive ink can be heated by electricity, resulting in colour change.

Electronic possibilities have inspired many artists for origami applications. Muscle wires are added to paper just as LED’s and sensors. It turns out to be difficult to find break-through applications, although paper is one of the most intensively used materials. One of the applications is in education, but they can be regarded as pure technology push. The question is if the technology can be integrated in existing products to enrich the interfacing functions.

Figure 11 A scene from a workshop

Light Touch Matters [9]

The Light.Touch.Matters (LTM) project is an EU-funded FP7 collaborative research project initiated and coordinated by Delft University of Technology with 17 partners in 9 EU member states. The project

started in February 2013 and will run for 3.5 years, promising to deliver three key results: a new family of smart interface materials, several ‘technology demonstrators’ that showcase the potential of these materials, and a methodology for so-called design-driven materials innovation (Miodownik and Tempelman. 2013).

Traditionally, innovation in the domain of industrial product design has been limited to the product level, i.e. to the generation of new product designs, with only occasional excursions by product designers into the field of manufacturing engineering, and virtually no attention for new material development. And even when designers address manufacturability or material innovations, it is to overcome a specific challenge posed by their product design: in this respect, the Panton chair represents a good example, with the designers and manufacturing engineers collaborating closely for years to realise this ground-breaking design.

Consequently, materials R&D is normally conducted more or less independent of envisioned applications in product design – or increasingly, with a set of target material properties in mind that are considered essential for certain key applications: here, the development of high strength steels for the automotive industry comes to mind, but many other examples can be found.

As an alternative, the LTM project, along with two similar EU projects under the same research call, explores design-driven materials innovation: the joint development of new materials through the deliberate interplay of designers and materials researchers. Key to this exchange is that not only objective material properties are addressed (e.g. strength, cost, thickness), but also subjective, experiential properties (e.g. aesthetics, tactility, evoked meanings). This way, the EU hopes to shorten the time-to-market of new materials and to combine the innovative forces of product design and material R&D.

Such ambitious targets can only be realised by narrowing down onto a specific, well-defined focus. For the LTM project, this focus is first and foremost the ‘technology suite’ that is taken along. The project aims to make thin, flexible and formable materials that combine touch sensitivity with luminous response, suited for product interface design. The materials themselves are hybrids, combining so-called piëzo plastics (themselves a composite of polymers and piëzo-active particles: these are the result of a recent breakthrough at Delft University of

Technology) with flexible OLEDs (see Figure 10): the former provides touch sensitivity, the latter luminosity. To add a certain ‘richness’ to the mix, the OLEDs will be equipped with a specific coating to provide colour effects (existing OLED colours are effectively aimed at either displays or lighting: the LTM project is more interested in ‘signage’ applications, which invite other outputs) and with a tactile top layer; a fourth layer on the bottom provides control, for instance, to distinguish simple on-off tapping from swiping, or to sense different levels of touch intensity.

A second way of focusing is the selection of the application area. Although no specific products are in- or excluded per se, the main attention goes out to products for care & well-being. Not only is this a key growth market, with e.g. the aging society requiring more and more products that allow seniors to live independently, and with obesity and other affluence-related afflictions generating a need for specific products to monitor health, eating patterns and so on, but it is also an area where intuitive-to-use, attractive and non-stigmatizing products can make a real difference. (A third reason for selecting a specific niche such as this is that it allows building up an equally-specific consortium: indeed, all design partners in the LTM project have a strong track record in products related to care and/or well-being.) At the time of writing, the LTM project is just getting underway. However, some immediate findings are of interest here already, such as the key role of early material samples to feed into the design stream, the need to express target material properties clearly in terms that designers can understand and relate to, and especially the ambiguous meaning of the word

‘material’: what designers can consider as a smart interface material is usually seen by the material researchers as a structure, device or similarly more encompassing term. Clearly, looking ‘outside in’ i.e. taking the designers POV presents a different picture than looking ‘inside out’ i.e. seeing as the material researchers do. In a similar vein, what the designers may consider as a ‘material’ property (e.g. touch location sensitivity) can purely technologically perhaps better be seen as a result of how the smart materials are integrated into- or onto a product.

www.light-touch-matters-project.eu [14] Air pressure interfaces [10]

The preceding examples were based on high-end materials technology. This last example of interactive material systems is based upon traditional elastomers, pneumatics and dynamics. However, these technologies are combined in the framework of modern design- and manufacturing technology. Computer aided design and simulation are combined with layered manufacturing technologies.

The dynamics theories were necessary to develop several basic forms which lead to a certain shape change under pressure. With special software these deformations could be simulated. It was important to

Figure 12 Layers of the LTM system

achieve that a physical object would react exactly the same as the virtual object. By producing the physical objects in layered technology, using flexible materials this could be realized.

Next step was to build in these forms in more complex shape changing objects, built with the same material. Change changing components and air ducts could directly be integrated. Also these objects could be virtually manipulated by special software.

The results of this project are amazing. Conclusions are:

- Applying this technology it is possible to realize in a cheap way complex shape changing objects.

- The control is realized using computer controlled cheap air pumps and valves. - The object has become a sensor. Pressure on

a spot leads to pressure in one or more air-ducts, which could be translated by the computer in a response.

The overall impression of the result is that of a living character. When translated to robotics the realization of systems with rich expression will be possible.

4. SMART MATERIAL INTERFACES

AND DESIGN PRACTICES

The potential of smart materials could lead to a principally different way of designing interfaces. Until now, designers were, with respect to interfacing, dependent on the limited possibilities of affordable technologies and components. Because of the rapidly growing possibilities, designers now have much more choice, which makes the design process more complex. The question is not just what information the user and the product should exchange, but also how the user would like to communicate with the product. So, expectations, meanings and affordances all come into play. A

simple action of turning on a product will be subject of design. With smart materials, combined with modern sensing technology, there are hundreds of ways thinkable for doing this. In case of the vacuum cleaner we could just say “vacuum cleaner on”, point to it with our finger, give it a hug or put our foot on it.

In this light, important research is carried out by Philip Ross [11] in his PhD project “Ethics and aesthetics in intelligent product and system design”. Ross: “Intelligence in products and systems challenges design in terms of ethics, but also in terms of aesthetics. An essential characteristic of intelligent products and systems is that they portray behaviour in interaction. Designing such products and systems requires a language that relevance and motivation goes beyond ‘traditional’ static form aspects: It requires a new language of form that incorporates the dynamics of behaviour. What could this language be?”

Ross developed a method for designing the interface, based on analysis of activities as showed in figure 15. However, the learning process should be playful and, more important, mutual. The user learns about the product, but on the other hand the intelligent product learns about the user and his/hers preferences. Another aspect is that the learning process leads to an

Figure 14 Creepon the baby devil

emotional relation with the product which protects the product against dumping too early and supports sustainability.

The Fonckel, a product which resulted from the PhD work of Philip Ross, follows these ideas. Management of the light is realized by moving your fingers over the pleasantly formed ‘back’ of the lamp. With different finger settings different parameters can be controlled like brightness, focus and direction. Learning how to operate is a nice experience.

Important is the fact that Ross gives priority to designing the social activity. From that the dynamic form is derived and after that translated to the sensory-motor activity.

The result, the Fonckel lamp was successfully introduced in the market.

The ideas of Ross are applicable to all kinds of products.

4.1. Products will be like horses

Chapter 2.4 suggests that, for the design of smart products, horse riding can teach us a lot. Horse and rider form a team, communicating with a rich set of media. To test this proposition, a master student, Arnout de Bruin, was invited to project to apply the metaphor to the design of a vacuum cleaner. [4] De Bruin concentrated his research on communication by the device of a set of parameters:

- Dust bag level (How full is it)

- Product malfunction (Does not clean) - Power cord length (How far can I go)

- Direction of wheels (Do I pull in the right direction?)

- Vacuuming task (Is the surface clean?) - Are bristles out or in (Adaptable to flooring) In this paper we will not go into detail, but some relevant results will be discussed. The fact that the

user would like to know if vacuum cleaning on a certain spot still makes sense, had never been an issue for manufacturers. It turned out to be possible. A particle sensor in the nozzle was integrated. Some examples of means of communication are illustrated below:

Figure 16 Fonckel of Philip Ross

Figure 19 Air is moving, device is working (moving bubbles)

Figure 17 Cleaning versus not cleaning

With help of an internet consumer research site, it was investigated if users would understand this form language. The result was that the semantics were understood well.

From an ergonomic side it was interesting to notice that the communication about the cleaning process should not be on the device itself, but on the nozzle. That is where you look at during the cleaning process (compare: the true controls of a horse are not the reins but the saddle, as every experienced rider knows).

Not every proposed medium was feasible yet, but, as an example, the change of colour in the nozzle was realized as a proof of principle. As an industrial design student, de Bruin worked for some weeks in the laboratories of nano technology at the University of Twente. It was the first time that a project was carried out in that laboratory aimed at a practical product development.

Our thanks go to Arnout de Bruin, but also to, Dr. Dhaval Vyas as his coach and the laboratory of Prof. Dr. Julius Vancso where the experiments with colour changing materials were carried out.

5. CONCLUSIONS

The aim of this paper is to introduce a new paradigm for product interface design under the label “organic interfaces”.

First of all, the consequences of intelligence in products for the relation between man and product were discussed. An important conclusion is that products should not be defined anymore by requirements of a product, but by a ‘contract’ in which the cooperation between user and product is described – with technology and design now allowing this contract to be unwritten, i.e. fully intuitive interaction..

Secondly, a limited inventory is made of the technologies which make organic interfaces possible. It can be concluded that interesting technologies are in the pipeline of research or even emerging from it, but that only a few are mature enough to apply in mass products. However industrial designers should anticipate the possibilities of these technologies by developing of a vision and design methods and tools – indeed, by actively getting involved in the materials research, as happens in the Light.Touch.Matters project.

Thirdly, attention was paid to design practice. A case study of Philip Ross’ lamp was presented, as was a vacuum cleaner by Arnout de Bruin. It can be concluded that there is no shortage of ideas about how to deal with the development of smart material interfaces.

Does it really make sense to use horse riding as a source for inspiration to develop ‘organic’ interfaces? In case of the vacuum cleaner it seems so. The nozzle provides information about pressure and dust flow. Not only does it provide the user with this information, but it can also make its own decisions based on this sensing, for example to optimize electrical power. It not disobeys like a horse can, but maybe this will exploited in future concepts.

However, this vacuum cleaner has started to look a little bit like a horse. It communicates with body language and manages an own agenda. For products to be expressing ‘body language’, a lot of technology still has to be developed. Passive colour changing materials are proven to be possible, but are not yet applicable on a large scale. The same counts for shape changing materials. In a horse this technology is present but it is difficult to imitate. Then again, the potential pay-off for ‘organic interfaces’ is huge: essentially, every product on the planet.

REFERENCES

[1] Poelman, W.A. 2005, Technology Diffusion in

Product Design. PhD thesis, Delft University of

Technoloy, The Netherlands, Design for Sustainability Program, publication 11

[2] Verbeek, Peter-Paul, 2005 [De daadkracht der dingen. English], What things do: philosophical

reflections on technology, agency and design:

translated by Robert P. Crease, ISNN 0-271-02539-5 [3] Schön , D., 1967, "Technology and Change--The

New Heraclitus" Delacorte Press,

[4] Vyas, Dhaval and Poelman, Wim and Nijholt, Anton and De Bruijn, Arnoud 2012 Smart material

interfaces: a new form of physical interaction. In:

ACM SIGCHI Conference on Human Factors in Computing Systems, CHI 2012, 5-10 May 2012, Austin, TX, USA.

[5] http://electrochem.cwru.edu/encycl/

[6] http://www.cesma.de/Applications.544.0.html?&L=1 [7] C Yang and C-P Fritzen 2012 Smart Mater. Struct.

[8] Lelieveld, Ch. 2011, Smart Material Systems for Architectural Applications, PhD thesis, Delft University of Technology, The Netherlands

[9] www.light-touch-matters-project.eu

[10] R. Slyper and J. Hodgins, 2010, Prototyping Robot

Appearance, Movement and Interactions Using Flexible 3D Printing and Air Pressure Sensors

Disney Research Pittsburgh, 4720 Forbes Ave Ste 110, Pittsburgh PA 15213 and Carnegie Mellon University, 4000 Forbes Ave, Pittsburgh PA 15213 [11] Ross, Philip, 2008 Ethics and aesthetics in

intelligent product and system design PhD Thesis

Eindhoven University of Technology, ISBN: 978-90-386-1474-8

[12] Ball, Philip, 2009, Shapes, Flow, Branches –

Nature’s Patterns, a Tapestry in Three Parts, Oxford

University Press, Oxford, UK

[13] Frens, Joep, 2006, Rich Interaction, PhD Thesis, TU Eindhoven, the Netherlands

[14] Erik Tempelman and Mark Miodownik, 2013,

Light.Touch.Matters – The Product IS The Interface,

Materials Matter VII, Material ConneXion, New York, USA

[15] Tatsuya Kaiho and Akira Wakita 2013, Electronic

Origami with the Color-Changing Function,

Proceedings of the 2013 ACM Workshop on Smart Material Interfaces, Sydney, Australia.