Motivation

Since the COVID-19 pandemic lockdown, tangible prototyping and quick idea validation at home environment with limited resources has been challenging. Cardboard has been commonly-used for crafting and quickly validating an idea in a tangible way . Inspired by the cardboard prototyping approach, we were interested in enriching the prototyping process at home where has limited material source and tools, and utilizing wasted materials other than a cardboard box.  

We asked the following research questions; 

How can we help the development of a tangible interface at home where has limited material source and tools?  Can we utilize any wasted materials other than a cardboard box? How can we recreate the wasted materials to be adaptable to functioning prototyping materials? What would be a way to rapid prototyping shape-changing materials at home? 

Observing a material consumption behavior of household that produced lots of wasted plastic packages, we inspired from the concept of upcycling–preventing wasting potentially useful materials by making use of existing ones– which was first solidified by McDonough and Braungart [Cradle to Cradle: Remaking the Way We Make Things, 2002].

Contributions

1. Exploration of a new design space of using wasted materials from thermoplastic bags with applying of FFF 3D printer without requiring modification of the printer to create interactive tangible materials and inflatable structures.
2. Providing a material library by characterizing 8 different thermoplastic materials wasted from daily household and a 3D printer setup optimized for each material to be upcyled as a functioning material for TUI, and evaluation of its durability in response to pressure.
3. Demonstrations of design primitives and use-cases that could contribute to playful learning, rapid prototyping and idea validation.

Method and Design Space

Therms-Up! DIY upcycling method allows users easily idealize and validate their ideas using a 3D printer without any customization or using clothing iron at home.

The FFF-type 3D printer can be applied not only for heat-sealing the wasted thermoplastics but also texture patterning, embossing, origami crease patterning as shown below.

(a) Multistable origami pattern created on the cereal bag. (b) Expandable origami cylinder
pattern for (h). Mountain (C) and Valley (b) folding line, (e) patterning the both of mountain and valley folding line is completed in a HDPE shipping envelope (used for fabricating the Fig. 6) Origami inflatables made of a cereal bag: (f) Multistable origami inflatable inspired (g) Miura-fold inflatable, (h) Expandable origami structure while twisting.

We explored a new design space as illustrated above using of wasted plastic bags combined with FFF 3D printer. Thermoplastic bags are easily found from household product consumption, such as food packaging, shipping, food delivery, and grocery shopping. Using the heat responsive characteristic of the thermoplastic, stiffness, and the plastic package’s unique layered-structure, we explored a design space that can create a new function out from the wasted material to be a tangible interactive interface such as inflatable, sensor, fluidic interface, and prototyping material. The benefits of using the wasted plastic bags are that we can apply the existing colors and printed images of the plastic bags, and choose various sizes that have already heat-sealed edges which minimize the fabrication time. By controlling the multiple parameters of 3D printer, we were able to create different patterns on the surface of the wasted plastic bag as demonstrated in the following section.

Mor et al. [Venous Materials, 2020] introduced a interactive fluidic mechanism made of Polydimethylsiloxane engraved with micro fluidic channels. The method we showed in Fig. 7 can be applied to quickly create the interactive fluidic mechanism at an affordable level for general people at home. Also, the zipper of the Ziploc allows users to replace the injecting fluid material whenever they want so that might be applicable to try the fluidic mechanism multiple times with different colors, and viscosity, and to test the design prior to directly producing the final prototype to reduce the waste of expensive materials.

Material Characterization

Table shown below shows 8 different thermoplastic bags that mostly wasted from grocery stores and home and corresponding settings of 3D printer and iron. We have collected thermoplastic bags consumed by a 4-person family over 3 weeks. All the material examples presented in this paper were from this collection. We first categorized the thermoplastic bags into 6 types based on its source product’s purpose. These were mostly from food and product packaging (Ziploc (a),
retort food container (h)) snack bags like chips and cereal (f)), shipping (package envelopes (d, e), bubble wraps (g)), plastic bags for food take-out, delivery, and grocery shopping (b, c). Then we categorized them depending on its sealing layer material. Thermoplastic bags we used here are identified as either high-density polyethylene (HDPE) or low-density polyethylene (LDPE), except for Ziploc which is made of polypropylene (PP). Other than the snack bags (f) and retort food package (h) which are consist of multiple layer, all the material shown in the Table are single layer of PP/PE. The material of plastic bags can be identified by the recycle code  that is labeled on the product package.

Characterization of different thermoplastic packages based on temperature (right), and the corresponding material example photos (left). 3D printer setting shows the required extruder temperature, extruder height from a printing bed, travel speed, usage of cardboard underneath the material and aluminum foil on top of it. Whenever using an iron, we recommend to place a aluminum foil between the plastic bag and the iron to prevent the melting of material and sticking to the iron, and to evenly distribute the heat. Detailed instructions can be found in GitHub

Examples of Inflatables and Materials

(a) 3D printer setup for heat-sealing ((b) in case of using a aluminum foil). (c) A actuator made of HDPE shipping envelope in bending motion referenced a folding pattern from [25]. (d) HDPE shopping bag inflatable with pre-folded layer to achieve a larger volume change. (e, f) inflatables having a bending mechanism introduced in [aeroMorph, 2016]; made of a chocolate cookie bag (e), and (f) bubble wrap heat-sealed with a HDPE shopping bag. (g) Soft actuator made of Ziploc and actuated by injecting water/air, (h) Cushioning patterns heat-printed on a LDPE shopping bag.

Applications

Creating Sensors

The aluminium layer of multilayered plastic bag, such as a retort food package, can be applied to fabricating a sensor. We created a capacitive based sensors as shown in above. The advantage of using the thermoplastic material is that we can stick the sensor path or trace to any other plastic materials by applying heat. To demonstrate this idea, we cut the walnut plastic package in two identical square shapes and sticked them to a HDPE shopping bag using a iron (Fig. below.(a.1)).
We created a simple inflatable with the sensor patch on each side, which detects its shape-deformation by capacitive variance due to the varying distance between layers (Fig. below.(a.4)). Also, by using the zipper attached on the walnut package, the pressure sensor’s material property can be adjusted by adding a sponge inside of the sensor bag.

Two use-cases of retort food package (a package of walnuts) for capacitive sensor application: (a) Monitoring of shape-deformation of inflatable pouch, (a.4) Capacitive response depending on the shape-deformation of the plastic air pouch. (b) Pressure sensitive touch sensor with a adjustable stiffness

Quick idea and concept validation 

Designing a smartphone stand with lamp: Use-case scenario of a designer who needs to quickly prototype and validate his/her idea by actuating cardboard prototype using HDPE plastic shopping bag inflatable.

Developing a Playful Educational Program Kit 

Learning a human anatomy and muscle and bone mechanism through upcycling a plastic shopping bag to create inflatables