Multispecies design: 3D-printed biomimetic structures to enhance humidity levels

Abstract

The paper changes the focus of the design debate from a human-centered design methodology to a posthuman design that takes both human and nonhuman agents into account. It examines how designers might use a multispecies perspective to produce projects with distinguished intelligence and performance. To illustrate this, we describe a project of structures for plants that started on a course in an academic setting. The project methodology begins with “Thing Ethnography”, investigating the movement of a water bottle inside a house and its interaction with other objects. The correlation between water and plants was decided to be further expanded, considering how water might enhance the environmental humidity and create a cooler microclimate for indoor plants. According to their effectiveness, 3D-printed biomimetic structures were designed and manufactured as water droplet supports considering different materials, and positioned in various configurations around a plant. Humidity levels and temperature of the structures were measured. As a result, this created a novel method for mass customization and working with plants. The paper discusses the resultant evidence-based design and the environmental values related to it.

1 Introduction

For more than three decades, the human-centered paradigm has dominated design. Because of the effects of technological and environmental transformations, designers are today faced with the task of working on complex socio-technical systems (Forlano, 2017). The research shifts the focus of the design discussion from human-centered design (Norman, 2013) to posthuman design (Forlano, 2017), which considers both human and nonhuman agents. It questions how designers may utilize “design for all-life” (Boradkar, 2015) and multispecies approaches (de Ruiter et al., 2005) to create effective projects.

The paper offers a posthuman interpretation of the term “user,” moving away from anthropocentrism (Crutzen & Stoermer, 2021) and toward biocentrism (Lanza & Berman, 2010). It exemplifies emergent design techniques that highlight the post-humanism discourse (Braidotti, 2013) and makes a case for including nonhuman lifeforms as partners in design research, either as informants and co-designers or as users. As a novel contribution to the field, the work extends traditional understandings of the “user” to nonhumans and questions the field of action for the contemporary design practitioner. To demonstrate this, it shows a project that started on an academic course and involved designing a set of structures for plants. So, the project’s objective was to build structures that would act as supports to store sprayed water, resulting in a cooler and more humid microclimate for indoor plants, primary users, and humans.

The project methodology begins with “Thing Ethnography” (Giaccardi et al., 2016) to examine the movement of a water bottle inside a home and its interaction with various objects. Given that plants are impacted by low humidity and heat excess in indoor contexts, with the discoloration and brown-colored tips of certain leaves, and that water may be utilized as a material to create a cooler and more moisturized microclimate, the link between water and plants was chosen to be further explored. Especially in hot climates, constant air conditioners decrease the low humidity levels even more. According to the biocentric viewpoint, all living things are morally equivalent and deserve the same respect. Biocentrism forces individuals to reconsider how humans and nature interact, contending that neither humans nor other living things are inherently more valuable than the other. It suggests that humans are only one interconnected species that depend on other species for survival and development (Lanza & Berman, 2010). So, humans are considered in a biocentric scenario, but they are not in the center of the chain, such as in an anthropocentric view.

The paper expands on that idea and analyzes indoor plants’ ergonomics, the ideal conditions for them to thrive, their relation to humans, and how plants and people establish a mutualistic relationship in a win–win scenario. Ideal humidity levels are essential for both species to survive; therefore, improving one will surely benefit the other. Especially in dry climates, people already have the habit of spraying indoor plants’ leaves with it; it is a standard and interesting procedure (Robinson, 2022) that helps the plant to thrive and the two species bond. Also, some plant species don’t thrive at all if the internal environment is with low humidity and high temperatures. The question might be how indoor plants and humans could enhance their interdependence condition in a future scenario, especially considering that currently, we spend ninety percent of our time in indoor environments (Sturgeon, 2017).

Therefore, water was introduced into the project to intensify humidity using 3D-printed biomimetic structures as water droplet supports. These design choices improved with time and changed in response to their performance. The structures can be joined and placed in many configurations around the plant as architectural features staged around the plant specimen, as long as they do not block the sunlight from reaching the leaves. These arrangements were significant because they enabled the creation of an evidence-based design optimized for plant health and performance. An indoor hygrometer, the Inkbird ITH-20, and a thermal camera, Thermal Imaging IR0018 resolution 35,200 px, were used to measure the structures’ humidity levels and surface temperature change.

It is important to clarify that the term “structure” in the paper is approached regarding not the material performance of sustaining a load, with established structural testing, but as a recipient for the water droplets. The 3D-printed meshes were observed and evaluated: the ones that were too fragile or rigid were discarded, and the one with a better water retention performance was chosen. Also, it is essential to highlight the term biomimetic, which means that inspirations are elicited from nature to design practical materials and systems that can imitate the structure and function of native biological systems (Sarikaya et al., 2003). In this project, a study on biomimicry (Benyus, 2002) was carried out to understand better how to create a cooler and more humid indoor microclimate using a sustainable passive strategy (Khelil and Zemmouri, 2019) without relying on electricity and how the structures could be connected effectively using the same material and manufacturing technology. Three biomimicry case studies were used in the design process of the 3D-printed structures: the Darkling beetles in the Namib desert (AskNature, n.d.), Warka Tower and Bird’s Feathers Interlocking Systems (AskNature, 2018).

Consequently, this created a unique and unconventional approach to working with plants as nonhuman actors and recognizing the potential of “other-than-human” perceptual capabilities and mass customization. The findings suggested that we better understand nonhuman design, ergonomics, and design performance to obtain insight into desirable nonhuman scenarios. In this case, it included understanding the ergonomics of the plants: shape and sizes of the structures, their gripping mechanism to the different stems’ sizes and formats of varying plant sizes and typologies, arrangement and placement of these structures, and possible materials—also, design performance related to the mesh water retention, mesh condition (lightweight or heavy) and the structure’s joints, to be able to bend and connect. The main idea was to extend to nonhumans the same care and attention that people have when interacting with their bodies.

2 Posthuman design and multispecies theory

Technology breakthroughs are causing a blurring of the conventional dualistic systems of natural and artificial, human and animal, and human and machine. They highlight the new sorts of agency that nonhumans, environmental or technological, have in the world. A growing body of social theory has developed around ideas that try to explain this boundary-blurring and introduce relational, hybrid, and non-dual modes of thinking (Forlano, 2017). This paper focuses on one of these hybrid modes of thought, specifically the posthuman, for a design practice that significantly improves our comprehension of the numerous agencies, dependencies, entanglements, and relationships that follow current issues and questions facing the design field (Forlano, 2017).

The human-centered design approach is a practice where designers target human needs (Norman, 2013). However, the human species is merely one of many elements that shape our environments, and its agency is established through relational processes rather than predetermined. As design enters the social sector and handles problems in complex socio-technical systems, it is essential to switch to a larger perspective, such as posthuman design, which considers both human and nonhuman players. The work being done in post-humanist and post-anthropocentric disciplines argues that to understand the transitions on our planet better, we should start thinking of manufactured systems as networks that include a variety of living creatures and the agency structures that act in and around them.

In addition, design does not have to be seen as an affirmative discipline but rather as a process-oriented analytical tool. One area open to investigation concerns the design of re-interpreting man’s connections with other species and the environment, proposing future multispecies cohabitation scenarios. To explore multispecies worlds and learn about environmental challenges, designers must become acquainted with different methodologies, which are intended to be more than just a set of techniques but also distinct ways of behaving, thinking, and experiencing (Gatto & McCardle, 2019).

More than ten years ago, the term “multispecies” appeared in the context of biology and ecological sciences to designate patterns of co-construction of environmental niches and wildlife management (de Ruiter et al., 2005). New interpretations of the idea have been made possible by its relatively recent introduction to the field of anthropology. The idea of multispecies offers a foundation for rethinking the participation of nonhumans in design and related processes. It also broadens the definition of sustainability because investigating environmental problems from nonhuman viewpoints can produce different results from those predicted by technocentric approaches (Gatto & McCardle, 2019).

The research discussed in this paper suggests a speculative design incorporating the views of humans and plants to create a multispecies reading of humidity and temperature in interior spaces. From a biocentric point of view, all species are part of a system of interdependence. In this project, based on the concept of co-performance, we are posing the relationship between plants and human as mainly a symbiotic, mutualistic relationship in which the association created between plants and humans are much stronger than the sum of the parts. This project intends to understand how different interspecies relationships and reciprocities could be enhanced and cultivated. In this context, the terms “interdependent” and “inseparable” are used to characterize work that acknowledges the interconnection and inseparability of people and other living things, striving to expand the scope of ethnography beyond the limitations of the human experience (Locke & Ursula, 2015).

Because daily encounters between people and nonhumans occur mainly indoors, within a house, as opposed to in an open space, that was chosen as the research site for this project. The idea of multispecies opens up fresh insights into how nonhumans fit into the design and practices surrounding it. It can be challenging when participants aren’t actual persons because participation in design can be seen as a discourse between numerous users (Lawson, 2005). Before we can acknowledge the agency of other-than-humans, we must first experiment with design solutions that can help us hear what other-than-humans want to “say” and, considering that, come up with alternatives to our social, cultural, and economic models (Gatto & McCardle, 2019). Nonhumans can engage in the design process and greatly impact how it’s done.

3 Theoretical underpinnings for methodology

3.1 “Thing ethnography” – water

A design approach known as ethnographic research involves learning about the people who will use the designed things adopting observational methods, and interviewing procedures. The core idea is that better products or, at the very least, more pertinent design suggestions might result from a thorough grasp of people’s lives, habits, motivations, and difficulties. Anthropologists and ethnographers spend much time interacting with and living among the people they study. They engage in various actions to build academic credibility, including observing, taking pictures, recording, taking notes, interviewing, etc., and producing theories, texts, and publications based on these efforts (Nova & Léchot-Hirt, 2016). Designers utilize this information and ethnographic tools to generate new concepts, develop ideas, and implement them (Van Dijk, 2012).

Nevertheless, beyond traditional ethnographic research, this project was based on “Thing Ethnography”, introduced by Elisa Giaccardi and other authors describing ethnographic research done with nonhumans (Giaccardi et al., 2016). They argue that humans shape objects and that objects likewise shape humans. For that, it is necessary to use anthropological and design methodologies that give both people and objects an equal voice to recognize their ongoing interaction. They also claim that the objects that live in our homes exhibit varying levels of dynamism and positioning. In the project illustrated here, “Thing Ethnography” was made by examining the movement of a water bottle inside a house and its interconnection with other objects (Fig. 1). Water was chosen because it is essential to both human and nonhuman life. A water bottle is also one of the most active items in our houses because it moves around and inhabits many ecosystems.

Fig. 1

“Thing Ethnography”: studying the movement of a water bottle inside a house and its relationship with various objects

“Thing Ethnography” also asserts that observing movement exposes how things interact: they exist in communities of things and behaviors that are occasionally unique or overlapping. This information invites questions regarding their operating environments. The difference between our research and Giaccardi’s was that ours involved a simple investigation of the movement of a water bottle throughout the day. However, it was intriguing to learn which items a water bottle regularly interacts with and might eventually build stronger bonds with—specifically, the space between the plant and a water bottle. Therefore, the project’s initial question was: how to improve the interaction between plants and water?

The idea of co-performance is also included in this research. Kuijer and Giaccardi (2018) assert that co-performance understands artifacts as having the capacity to learn from and perform with people. From this viewpoint, co-performance acknowledges the dynamic differences in capabilities between people and objects and stresses the intrinsically cyclical relationship between the design of the object and its use. In our project, it was decided to focus on the coexistence of plants and humans. Both plants and humans develop a mutualistic relationship within situations where everyone benefits. Since nonhumans and humans depend on water and light to thrive, enhancing one will inevitably improve the other. According to the theory, co-performance enables both species to flourish and fosters more harmony between people, other animals, and the environment. Lovelock expands on this idea by claiming that the Earth is a self-regulating system (Lovelock, 2016).

3.2 Biomimicry strategies

The “Thing Ethnography” and the link between plants and water inspired the initial concept of building 3D-printed structures embedded with water that would provide the plant with a more moisturized and cooler environment indoors. This design requirement was observed due to the yellowing of some leaves caused by a lack of humidity in some indoor circumstances. Three biomimicry strategies were used in the design process of the 3D-printed structures.

The first and second were related to how to retain and save water. To collect water, some species of darkling beetles in the Namib desert have unique points and bumps on their wing scales. Air condenses on the tips, forming water droplets that fall off the bumps and into the beetle’s mouth (AskNature, n.d.). Similar to the beetle, Warka Tower collects atmospheric water vapor from rain, fog, or dew that condenses on the cold surface of the polyester mesh, creating droplets of liquid water that flow into a reservoir at the bottom of the tower (AskNature, 2017).

The third biomimicry case study discusses natural interlocking systems such as the ones existing on the birds' feathers, in which filaments of birds’ feathers connect with interlocking hooks and work as a “natural” zipper. A feather’s central shaft has around a hundred filaments on either side, each fringed by a hundred additional filaments known as barbules. The birds’ beaks comb the disordered and pushed-together feather filaments. The barbules’ hooks reengage like zip fasteners teeth, reestablishing a uniform and smooth surface (AskNature, 2018). These four biomimicry case studies were contemplated for the shape, geometry, and material to design the structures for better performance (Fig. 2).

Fig. 2

In the upper row on the left is a Darkling Beetle, in the center a scanning electron micrograph of the textured surface of the depressed places on Stenocara surface, and on the right an illustration of atmospheric water vapor condensed on the surface of the Warka Tower mesh. In the lower row, the birds' feathers interlocking system

4 Methodology

4.1 Shape and geometry

The project’s methodology began with a study based on “Thing Ethnography” and how the connection between plants and water would give the plant a cooler atmosphere and a more moisturized environment in indoor spaces. This requisition appeared because certain indoor plants’ leaves may become discolored due to a lack of humidity in certain situations (Iowa State University, n.d.). Low humidity is harmful to a lot of people and animals, especially in dry climates. Therefore, the interaction between people, indoor plants, and humidity levels was investigated. The recommended humidity range for humans is 30% to 50% (Koster, 2016), but the recommended range for indoor plants is 40% to 60% (Young, 2020). The range of ideal humidity levels for both indoor plants and people is between 40 and 50%. According to the idea of co-performance, while designing to improve one’s performance related to humidity levels, the other will immediately increase (Kuijer & Giaccardi, 2018). This research led to the concept of developing 3D-printed structures for plants that would produce a more moisturized environment and a cooler microclimate inside habitats that would be advantageous to both nonhumans and people.

The first stage of the design involved deciding on the external shape of the structures, which needed to be easy to assemble but also durable enough not to bend or break. Hence, the external shape was created using arrangements of triangles because they are stronger than rectangular shapes and may fold in a non-orthogonal manner. One technique for Buckminster Fuller to show the strength difference between the triangle and the rectangle is applying pressure to both. The triangle is far more rigid than the rectangle and can withstand pressure without folding up or becoming unstable. In fact, it is twice as strong as the rectangle (Buckminster Fuller Institute, n.d.).

The initial structure was composed of six triangles connected to a hexagonal core thanks to a “v” shape join design. Half triangles were twisted up and half down in an alternated fashion (Fig. 3). The connections between them, which were meant to be on the extensions of the edges of two triangles, suggested several design typologies. The structures were 3D printed using Polylactic Acid (PLA). An object interacting with the plant should be made of organic, degradable materials, just like the plant. In this case, PLA and water. Additionally, they must be lightweight to fit the plant’s ergonomics better. For effective storage and transport, they were produced as flat constructions that could be folded.

Fig. 3

First 3D printed structures: planar, folded, and other typology showing the connection

Textures based on Warka Tower (AskNature, 2017) and Darkling beetles (AskNature, n.d.) were analyzed to comprehend how water droplets might be kept within a mesh. But unlike the instances cited earlier, the 3D-printed biomimetic structures wouldn’t be able to collect water from the air. The suggested structures would act as supports to hold and store sprayed water, resulting in a cooler microclimate for indoor plants, primary users, and humans.

Parametric definitions were created with Grasshopper and Rhinoceros. Several meshes were tested to calibrate the pattern and layering. Initially, 2.5D sinusoidal and meander curve patterns were used in overlapping and non-overlapping layers. Cases with overlapping layers performed better, storing water between the waves due to surface tension. Testing other meshes with 1, 2, and 3 layers of 3D-printed PLA revealed that the two-layered mesh worked the best for this initial experiment (Fig. 4). The three-layered mesh could contain more water droplets but was rigid and heavy, while the one-layered mesh was insufficient to store enough water droplets. The two-layered mesh was tested on an Epipremnum aureum to verify ergonomic and design aspects, such as ease of aggregation, adaptability, and the ability to cling to the plant (Fig. 5). A first attempt to evaluate the capacity to enhance the water retention and the humidity condition was conducted measuring humidity level inside a cardboard box large enough to contain the plant. Twenty-five structures using the 2.5D patterns were measured alone, without and with water, and then applied to the plant (Fig. 6). This first configuration gave some interesting results. Still, it was decided to explore an alternative approach to configure the mesh to avoid laminar water retention, because this configuration is more effective if soaked in water rather than sprayed with water.

Fig. 4

2.5D mesh structures. In the upper row on the left is the planar configuration, in the center is the folded version, and on the right is the structures' aggregation. In the lower row, the first and second pictures are the structure with water; the third picture is a close-up of the structures’ interlocking system,  and in the last one, the structures arranged on an Epipremnum aureum

Fig. 5

2.5D mesh structures arranged on an Epipremnum aureum

Fig. 6

Photos of the 2.5D mesh structures without water (39% of humidity) and with spayed water (53% of humidity); structures arranged around an Epipremnum aureum without water (39% of humidity) and with sprayed water (62% of humidity)

The second strategy involved calibrating the toolpath geometry and extrusion settings to transform the pattern into a 3D arrangement. In this case, water is kept in the three-dimensional structure as droplets, ideal for sprayed water. The single layer outperformed the others (Figs. 7 and 8; Table 1). A significant volume of water can be stored in the one-layer 3D arrangement while keeping its strength and lightness, and the ones with two and three layers were rather heavy and hardly pliable. Consequently, the one-layer 3D configuration—P4-1—was chosen as the mesh for the final structures (Fig. 8; Table 1).

Fig. 7

Meshes with 2.5D and 3D configurations

Fig. 8

Square samples of the meshes with 3D configuration testing different stratifications and densities

Table 1 Performance chart of the meshes with 3D configurations. The meshes with a dry weight over 2.5 g or critical condition of the interlacement were discarded. The remaining samples were tested to identify the water retention in grams at ten sprays. The ratio between the water retention and dry weight allowed us to calculate a performance factor. The best performance was recorded from the meshes P4-1 and P4-2, and P4-1 was selected for the final structure

It was crucial to employ sprayed water throughout the process since people already use it to spray water on the leaves of indoor plants; therefore, it is a common and interesting method that aids in bonding the two species. Using these structures would improve water retention in this instance.

After noticing during the first pattern configurations (Figs. 4 and 7) that the mesh had undulations on the outer part that might be used to connect the structures, it was decided that only one typology would allow for multiple connections. So, the undulations on its outer half were emphasized to make the interlocking system more stable, and another biomimicry strategy was used related to the birds' feather interlocking system (AskNature, 2018).

The interlocking systems of the structures were designed according to a fractal-like organization and configured considering their performance and grip ability on the plant’s stem. An open-ended possibility of combinations was created using an interlocking system of a standard module employing the same material and process used for the mesh (Fig. 9).

Fig. 9

Interlocking systems are organized in a fractal-like manner and customized based on their performance and grip ability on the plant stem. The center one in the first photo, right on the second and third photos, performed better and was used for the final structure

After the above experiments, the structure’s design was condensed to a rhombus made of two triangles instead of two rhombuses made of four triangles. In the initial tests, the joint that connected the two triangles of the structure was part of the sinusoidal weaving pattern. It proved challenging to bend and occasionally broke, endangering the system’s stability. So, the joint on the 3D mesh-based structure was changed to a square wave to facilitate bending in various directions. The space between the triangles was lowered in the final configuration to improve stability and continuity between the modules (Fig. 10).

Fig. 10

Various joint kinds and sizes; test for the grip-ability to the plant’s stem; structures with different meshes

To better accommodate the various types and anatomical parts of plants, the structures were 3D-printed using the P4-1 mesh in two sizes: a smaller one measuring roughly 8 cm by 6 cm and a bigger one measuring around 10 cm by 7 cm. The small structure has a dry weight of 1.2 g; with three sprays, it passes to 1.5 g, and after fifteen sprays, it stabilizes to 2.8 g. The big one has a dry weight of 2.0 g; with three sprays, it passes to 2.3 g; after fifteen sprays, it goes to 3.6 g and stabilizes at 4.1 g after twenty-five sprays (Figs. 11 and 12).

Fig. 11

In the upper row, the small structure (8 × 6 cm) dry weight and wet weights with 3 and 15 sprays of water. In the lower row, the big structure (10 × 7 cm) dry weight and wet weights with 3 and 15 sprays of water

Fig. 12

Comparison of the maximum amount of water retained (g) between the small structure (8 × 6 cm) and the big one (10 × 7 cm). The maximum amount of water retained stabilizes after fifteen sprays for the smaller structure and after twenty-five sprays for the bigger one

5 Material development – 3D-printed organic materials

As the project progressed, the possibility of developing an alternative material for the foldable structures emerged. As previously indicated, the structures were 3D-printed using PLA. PLA is a bio-based plastic that is biodegradable under controlled composting conditions (Cosate de Andrade et al., 2016), making it a more environmentally friendly choice than oil-based plastics, which could take centuries to decompose and create microplastics. However, in the search for a more integrated system and to avoid relying on external end-life treatments, the research moved on using biodegradable, water-soluble organic materials that are at the same time nutrient-rich slow-release fertilizers for the plant. Working with the material system would enable the structures to better integrate their end-of-life with a smaller cycle, such as the plant’s life and growth. The structures made with these materials might encourage plant growth through deeper humidity and nutrient-boosting integration.

The study of different types of deficiencies in houseplants set the ground to identify a series of substances the plants need to have a healthy life. Nitrogen deficiency, for example, could be overcome with coffee grounds, tea, or other nitrogen-rich plants like beans and peas. Potassium deficiency, which causes leaves with brown spots, brown or yellow veins, or yellow edges, could be defeated with banana peels and calcium deficiency by using crushed eggs. Other substances, like cinnamon, can act as a natural insect repellent and be anti-fungal (Kowalska et al., 2020). In addition, it promotes root growth and overall plant health. The research will be further expanded, including different substances that form the nutrient sources necessary for plant growth, ideally recycling food waste and avoiding harmful chemicals.

The material tests were developed considering the use of Direct Ink Writing (DIW) 3d printing, an extrusion-based method using a highly viscous paste filament at room temperature (Chen et al., 2019). This technique is utilized for a broad range of liquid or semi-liquid materials, such as ceramics, polymers, and food. Therefore, the initial tests were conducted with extrusions using a 60 ml piston-based syringe with a nozzle of 2 mm. This method anticipates using the same syringe mounted on a three-axis 3D printer for CNC testing of the material. It is also considered the use of a Liquid Deposit Modeling (LDM) extruder equipped with a screw system capable of regulating the output flow of the material. In this way, it is possible to have a rapid flow interruption and good retraction control, which is difficult to achieve with the syringe-base extruder.

The goal of generating a biodegradable material that embeds nutrients led the research to focus on biological polymers, particularly polysaccharides, as they are abundant carbohydrates. Corn starch, cellulose, chitosan, and xanthan were the main substances tested to create different recipes for the printing paste (Fig. 13). This initial series of tests were conducted to evaluate three principal aspects. The first regards the preparation procedure, considering the difficulty of the steps, the timing, and the easiness of moving the paste to the syringe. The second concerns the behavior of the paste during the extrusion, more precisely, the difficulty of the material’s ejection and its capacity to keep the shape of the nozzle, creating a sort of filament from it. The last and probably most important aspect regards the curing time when the material solidifies. This drying phase was conducted with the sample at room temperature, and after 24 h, the paste reached a stable consistency. This phase was crucial concerning possible shrinkage that could alter the printed shape.

Fig. 13

Green tea and xanthan, green tea and starch, xanthan, sunflower seeds and xanthan, cinnamon and xanthan, cinnamon and starch, green tea and xanthan

Next, it was decided to work with recipes defining binder and filler, where the binder is one or a combination of the previously mentioned polysaccharides, and the filler constitutes the nutrient for the plant. Four testing ingredients were selected as fillers: cinnamon, green tea, coffee, and sunflower seeds. The coffee and cinnamon were already in a very fine powder; the green tea and the seeds were instead processed several times using an electric food chopper and a fine mesh strainer to reduce them to a fine powder. The powder format facilitated the mixing with the binder, creating a homogeneous paste, easy to extrude using the 2 mm nozzle. These initial tests were conducted by hand to simulate different movements overlapping the extrusions in meander curves, like the one tested with the PLA (Figs. 13 and 14). The intention was to evaluate the reaction of the extruded material and see its capacity to shape patterns with different pressures on the piston. The extruded samples were stored for air drying. After 24 h, the samples were stable and ready to test. The shrinkage caused a reduction in section diameter, but the patterns remained shaped as extruded. They were rigid enough to host the water droplets but brittle when connecting the structures together or to the plant’s stem.

Fig. 14

Coffee powder and xanthan in the syringe, fresh extrusion, and 24 h after drying and shrinking

A second series of tests was done to reduce the shrinkage and increase the pliability of the dry material, avoiding having a too-delicate module to handle. The initial recipes were improved with flour and tested with different ratios of binder/filler. The intention was to understand if adding flour could reduce shrinkage (Wei et al., 2022). The granular nature of the filler makes it good for compression, but it doesn’t work on traction. A series of samples were made using less filler than the binder to make the final piece more pliable. After several failures, a good result was achieved with a sample showing a limited shrinkage of 0.1 mm (Fig. 15). The same sample attained a stable shape that maintained the original configuration and enough elasticity to allow connections between them, even if it breaks instead of bending under strain. There is room for improvement and to achieve a pliable module, considering that these tests are just in a preliminary stage.

Fig. 15

Tests cornstarch flour and cellulose binder with a ratio binder-coffee filler 10:1

Regarding the biodegradation of these components, if they are soaked in water, they can be dissolved within 24 h. Considering that they are meant to be sprayed with water and because they also absorb the water droplets, the degradation process could take weeks. A preliminary test was conducted using small samples of the first iteration on an acrylic sheet and sprayed with water regularly. After a day, it was evident that the water was gaining color and dissolving the substances (Fig. 16). In the future, more tests could be conducted using the actual structures.

Fig. 16

Tests to analyze the reaction of the samples with sprayed water

These tests were made to understand the materiality and procedures from the ingredients to the final structure. The goal for the next series of tests is to rationalize and standardize the procedures. The different fillers could be used separately to have structures that tackle specific conditions of plant deficiency. Still, they could also be combined as a general fertilizer providing multiple substances to the plant. Future tests would use a mix of these components to evaluate the effects. The cold recipes need more investigation and refinement, but they have good potential due to their practical preparation. Another improvement regards the mechanization of the preparation with an industrial dough mixer to control the mixing speed. Because of the promising results, the recipes with less filler and the addition of cellulose will be investigated further and applied to DIW extrusion.

Certainly, the initial geometry designed for PLA must be altered according to the properties of the new material, in both the extrusion behavior, in other words, the capacity to generate the “curly” effect of the mesh, and the interlocking system. The natural air dehydration process demands time and storage space, so a test is planned to use an inducted drying process with an oven to guarantee the same conditions for the samples and to speed up the process.

Another test was conducted with these materials, in particular using a simple xanthan/coffee mixture spread onto the PLA structures (Fig. 17). This hybrid approach uses the fertilizing material in a different way to the previous one as the paste would cover the gaps of the mesh. As a positive aspect, this option makes the structures reusable for different applications. On the other side, spreading the paste is not easy to handle. Although the coated sample demonstrated that it could collect water (Fig. 17), more tests must be conducted to compare this option’s water retention and degradation time with the structure 3D printed in biodegradable material.

Fig. 17

Xanthan/coffee paste distributed in different quantities on the small structure (8 × 6 cm) and the big one (10 × 7 cm). On the right, weight analysis of the small structure (8 × 6 cm) dry weight with paste and wet weight after 5 and 10 sprays

As mentioned above, these tests using water-soluble organic materials are promising, but a more accurate investigation is needed to have more reliable processes and results. For this reason, the project used the PLA structures for the performance evaluation of the humidity and surface temperature of the plant. It is important to clarify that firstly it was necessary to understand if the concept of the structures would be effective using PLA 3D printed on desktop machines and after material tests could be done as an evolution. The next would be to compare the performance between the simple PLA, PLA with a biomaterial coating, and just the 3D printed biomaterial. Therefore, this paper was a proof of concept to analyze if the structures could affect the humidity level around the plant and its surface temperature.

6 Experiments set up and results

Different tests were conducted to stage various configurations around the plant itself following the amount of weight the plant could support in each portion. These arrangements were important because they enabled the creation of an evidence-based design optimized for plant health and performance. Fifty-five structures using the P4-1 mesh structures were used —thirty big structures (10 × 7 cm) and twenty-five small ones (8 × 6 cm)—were arranged around a philodendron (Fig. 18). In the first test, the plant with the structures was placed inside a cardboard box so an indoor hygrometer, Inkbird ITH-20, could measure the humidity level.

Fig. 18

3D mesh structures arranged on a philodendron

The initial humidity level was 42%, and after water was sprayed on the sole structures, with no plants inside, the humidity level increased to 55%. When this last step was repeated with the structures arranged around the plant, the humidity level changed to 63% because of the additional water droplets retained by the plant (Fig. 19). As indoor plants, besides succulents, need humidity levels from 40 to 60% (Young, 2020), the structures provided quite an effective change in humidity.

Fig. 19

In the upper row, from left to right, structures without water (42% of humidity) and with sprayed water (55% of humidity). Structures arranged around a Philodendron without water (42% of humidity) and with sprayed water (63% of humidity). In the lower row, structures arranged around the plant and close-ups with spayed water (55% of humidity)

Also, since plants can co-exist in indoor environments, contributing to different humidity levels, the concept of co-performance (Kuijer & Giaccardi, 2018) broadens our understanding of interdependence with other species, helping each other to regulate favorable conditions. The number of plants and structures could be a suitable regulation parameter for an indoor humidity level.

After two weeks of use and spraying just the structures once a day, the yellow and brown parts didn’t regress, but new discoloration didn’t appear on the leaves of these plants. Also, this system of spraying water is more efficient in plants from the rainforest that are used to having water droplets over their leaves.

Another series of tests were conducted without the cardboard box to verify the humidity levels and surface temperature of the plant in a realistic condition. The measurements were taken using a common indoor hygrometer, Inkbird ITH-20, and a thermal camera, Thermal Imaging IR0018 resolution 35,200 px, in an indoor space at 26˚C. For this series of tests, the P4-1 mesh structures were analyzed, comparing the small structures (8 × 6 cm) with the big ones (10 × 7 cm) version without water, with three sprays of water, and with ten sprays of water (Fig. 20). The thermal images help to verify that with more sprays the water distributes better and fills the whole structure.

Fig. 20

In the first row are the small structures, and in the second row are the big ones. From left to right, structures without water, with three sprays of water, and with ten sprays of water with their corresponding thermal images

The humidity level around the structures and surface temperature of the structures were measured on a group of twenty big structures (10 × 7 cm) and twenty small structures (8 × 6 cm). Then it was measured again after spraying ten times water on them on a separate surface to avoid having water droplets on the surface of the recording area. A change in humidity was recorded, and the thermal images show a change in the surface temperature of the structures from an initial 26˚C to a minimum of 23.5˚C (Figs. 21 and 22).

Fig. 21

From left to right, structures without water (56% of humidity) with ten sprays of water (62% of humidity) and the thermal image that shows a change in the surface temperature of the structures from an initial 26.5˚C to a minimum of 23.5˚C

Fig. 22

From left to right, structures without water (56% of humidity), with ten sprays of water (62% of humidity) and their corresponding thermal image showing that initially the surface temperature of the structures was 26.8˚C going to 23.5˚C after approximately 4 min

Humidity levels and surface temperature were measured for the plant without the structure and the plant with the structure, starting with a condition with no water and then testing differences when applied ten, twenty, fifty, and hundred sprays of water around the plant. The difference in the amounts of water sprayed was not so much related to a constant humidity increase as it was to the duration of the increased humidity level over time. With more sprays, the humidity level stayed up for a longer time. A difference in the humidity with the structures was recorded with lesser sprays (Table 2). It shows that the structure is very effective when spraying a modest amount of water on the plant because it collects what would be wasted without it. On the other side, the thermal analysis highlights the wet area’s expansion, lowering the structures’ surface temperatures and better diffusing the water around the plant (Fig. 23).

Table 2 Recording of the humidity level with different amounts of sprayed water. It is visible that after 20 sprays of water, the humidity level stabilizes. However, the time to go back to the initial humidity level increases according to the number of sprays

Fig. 23

In the first row, the Philodendron is without structures, and in the second row, with the structures. From left to right, no water, ten sprays of water, fifty sprays of water. The thermal images show the temperature cooling and the even distribution of wet areas when the structures are arranged on the plant, visible in the last photo on the bottom right

7 Conclusion

This paper moves the conversation about design toward post-humanism, which considers both human and nonhuman agents—the latter of which is frequently ignored in design processes. It begins with an interdisciplinary debate that integrates research on nonhuman design, ergonomics, design performance, and ideal indoor humidity levels to obtain insight into desired nonhuman surroundings. It also describes how a project to create structures for plants evolved into 3D-printed biomimetic structures holding water droplets, arranged around a plant in different patterns to raise humidity levels in enclosed spaces. The results demonstrate that the structures can enhance the humidity level and decrease the plant’s temperature, granting a better distribution of the wet area around the plant. The humidity level increased by 6%, and the surface temperature of the plant and structures dropped 2 degrees in an open environment. It shows that the structures expand the area of the plant able to retain water, and in doing so, they prolong the presence of enhanced humidity.

The findings imply that taking nonhuman actors into account can result in various design ideas and a mutualistic relationship scenario based on the idea of co-performance because the ideal humidity levels for people and plants in indoor spaces overlap between 40 and 50% (Koster, 2016; Young, 2020). The project’s potential development expands the role of the material using nutrient-filled biodegradable organic substances, incorporating the end-of-life of the structure into the discussion as part of the plant’s growth cycle.

The study develops a fresh method for collaborating with plants as nonhuman actors and appreciating “other-than-human” characteristics. Expanding traditional understandings of the “user” to nonhumans and connecting it with 3D printing and mass customization makes a new addition to the design profession for contemporary practitioners. It examines the evidence-based design and the environmental values we aspire to see our society adopt, with significant ramifications for present and future design guidelines.