Breathing Life into Slime: The Creation of Kinetic Sculptures from Non-Newtonian Fluids Free

As we stepped into the workshop, a sudden scream greeted us. Turning toward the sound, we saw a girl showing her friends her hand, which at first glance appeared to be melting. While we were still in shock, a burst of laughter followed. A boy began playfully shaping the girl’s “melting” hand, calling himself a sculptor. As this amazement was not enough, he inserted a straw into the hand and, after he blew into it, the hand began to expand as if inflating. Had the location not been a department store, we might have believed we were in a sorcerer’s chamber based on what we had observed. But, of course, we were far from any ancient magic. The setting was a recently popular workshop in Taiwan, and the melting part of the kid’s hand was a flesh-colored slime.

Slime is not a recent invention; children have enjoyed the gooey material since its invention in the 1970s. Since the 1980s, Polyvinyl Alcohol (PVA)–based slime has gained widespread popularity in classrooms and workshops [1]. In recent years, social media has played a significant role in reviving interest in slime, particularly among children and teenagers, who love creating it from scratch [2–4]. As artists and researchers who enjoy exploring new materials for kinetic sculptures, we participated in one of the workshops to experience this fascinating substance.

In the workshop, one of the highlights was the creation of a “slime bubble,” which enchanted all participants. The process involved stretching slime into a wide sheet and then quickly placing it against the ground to trap air underneath, creating a gigantic bubble [5]. From what we experienced, slime bubbles differ significantly from common artificial bubbles (e.g., soap bubbles) in their stretchability and durability due to slime’s polymer structure and non-Newtonian fluid (NNF) properties [6]. In contrast to the fragile nature of soap bubbles, slime bubbles exhibited a remarkable resilience to touch and gentle manipulation. When they were pulled apart, they didn’t burst instantaneously but slowly separated, like a piece of shed skin. Overall, given its supple and damp texture, the tactile experience of a slime bubble evoked the sensation of touching a living organism. This workshop experience inspired us to consider slime bubbles as a medium for creating new kinds of kinetic sculptures.

While most slime workshops focused on creating a single gigantic bubble to attract children, our interest lay in the collective interactions among multiple slime bubbles. For kinetic sculpture, the movement of a single inflating slime bubble was limited, offering only growth and rupture without much variation. Therefore, we envisioned utilizing multiple slime bubbles as repetitive elements in such kinetic sculptures, and we speculated that the interactions among bubbles could potentially expand the dynamics of the collective movement. Using repetitive elements in kinetic sculptures is a widely adopted technique. Anthony Howe is among the artists who frequently utilize this approach [7]. He often starts with a single element and replicates it to build an entire sculpture. Take Octo as an example: Driven by the wind, each component interacts with its neighbors, collectively evolving into an organic movement that evokes images of jellyfish [8]. Interestingly, the forms of real jellyfish and other living organisms are also the result of the interactions of multiple similar elements, which are cells. Yet what sets living organisms apart from kinetic sculptures is that cells grow and die constantly [9], but as a whole, they miraculously continue to construct the forms of living entities.

Drawing inspiration from this concept, we utilized airstones—porous objects often used in aquariums to diffuse air—to inject air into the slime, creating hundreds of bubbles that we saw as living cells that grew and died (ruptured). Surprisingly, these bubbles collectively exhibited behaviors rarely observed in kinetic art. They grew and ruptured, unpredictably interacting with one another, dynamically shaping the bodies of the sculptures. While we delighted in the spontaneous interactions of the bubbles, this unpredictability also meant that the precise details of the sculptures were beyond our control. Nevertheless, we found that by manipulating parameters such as airstone movements and air injection timing, we could guide the overall contours of the sculptures. Our experiments with different parameter settings evolved into several “sculpting” methods, enabling us to craft various types of slime sculptures.

In the following sections, we introduce slime’s NNF properties, how we made it from raw ingredients, and how we exploited its physical nature for sculpting. We discuss the interactions between slime bubbles that shaped the sculptural bodies. We then describe the creation of a slime sculpture and the methods we developed. We share our experiences from the first exhibition in Taiwan, where audience feedback prompted us to make adjustments for the following exhibition at Ars Electronica in Austria, where we had to modify the ingredients to accommodate the completely different climate there (Fig. 1).

Slime’s unique properties distinguish it from ordinary solids and liquids. When rapidly struck, it behaves like an elastic solid, yet it flows like a liquid when gently pressed, showcasing its NNF nature. Unlike Newtonian fluids, whose viscosity is constant, NNF change viscosity under different circumstances. The slime for slime sculptures lies in a subclass of NNF called Shear Thickening. In this category, materials change their viscosities with applied forces, becoming more solid-like under high shear rates and more liquid-like under low shear rates [10,11]. This characteristic enables the creation of highly malleable forms: When it behaves more like a liquid, it allows us to reshape its form without breaking the sculpture; when it behaves more like a solid, the bubbles hold their shape longer and more firmly. Additionally, blowing air through the torn part of the solid-like slime produces sounds that interest viewers. By taking advantage of NNF properties, slime sculptures offer unique visual, tactile, and auditory experiences.

Considering that varying ingredient proportions significantly affect slime’s properties, we chose raw ingredients over commercial slime for better quality control. This decision led us to develop PVA-based slime, which consists of a PVA solution and sodium tetraborate (borax) [12]. The interaction between PVA and borax creates intermolecular connections among the PVA chains through weak bonding with the hydroxyl groups in PVA [13]. It is this specific interaction that gives the slime its NNF properties. During experiments, we found the ratio of PVA to borax was crucial in preventing premature bubble rupturing, as borax increased viscosity. Additionally, adding glycerin enhanced stretchability, allowing more bubbles to form and grow. The slime-making process involved mixing these ingredients and kneading until smooth and stretchable (Fig. 2a).

The temperature and humidity in the environment also affect slime’s condition. Therefore, for each exhibition, we had to adjust the proportions of ingredients to align with our goal, which was to ensure that by gradually infusing air through an airstone into the slime, numerous bubbles could expand consistently without bursting, maintaining a steady growth rate (Fig. 2b). In this way, those slime bubbles could interact with each other, collectively merged into a series of dynamic movements that became the body of a slime sculpture.

A slime sculpture forms from bubbles created by passing air through a slime-coated airstone. An airstone’s numerous micropores are key to generating bubbles. When air flows through those micropores, it produces hundreds of bubbles that interact with each other, collectively shaping the overall form. During experiments, we identified three distinct collective behaviors that dynamically shape the body of a slime sculpture.

An airstone’s dense micropores create competition for space as slime bubbles grow. Typically, one or two bubbles would expand rapidly, dominating the space and suppressing the growth of others. The suppressed bubbles then sought out gaps around the dominant bubbles to grow, creating a dynamic competition. Eventually, due to the imbalance of the slime’s internal force or gravity’s drag, one of the largest bubbles would rupture and collapse, ceding its place to others (Fig. 3a). At this point, the ruptured bubble’s residues dropped on the airstone’s surface. The residue displayed more like a liquid from this moment, filling the empty part of the airstone’s surface. Once it covered the area, a new bubble would emerge. This cyclical process of growth and demise resonated with the life cycles of living cells and multicellular organisms, where millions of cells are born and perish every second yet collectively maintain a consistent dynamic form.

Normally, as we continued to supply air, the bubbles kept growing and competing for space. However, when the wall between two adjacent bubbles ruptured, we observed that the smaller bubble would shrink while the larger one continued to expand as if they were competing for air (Fig. 3b). This phenomenon could be explained by the well-known two-balloon experiment in physics [14]. When two rubber balloons are connected with a valve, once the valve is opened to allow air exchange, the sizes of the balloons do not equalize. Instead, due to the differences in pressure in the rubber, the smaller balloon deflates further, while the larger one inflates more, as if the larger balloon “devours” the smaller one, winning the competition for air.

Besides competitions, we observed an intriguing behavior. This phenomenon occurred when the dominant bubble was so gigantic that it started covering other bubbles. In this situation, the dominant bubble would not interfere with the growth of others. Instead, they would grow together. Interestingly, this behavior usually occurred after the slime bubbles had developed for a while. From the viewers’ perspective, it seemed as though the dominant bubble, after competing for space and resources, suddenly chose to protect others by covering them. This phenomenon led us to have an interesting visual and tactile experience: When we tore up the dominant bubble, those smaller ones suddenly showed up, almost as if the sculpture was giving birth to the tiny ones (Fig. 3c).

Although slime bubbles are inorganic, these interactions among them closely reflect the concept of Living Images in Bioart introduced by Juppo Yokokawa, Nobuhiro Masuda and Kazuhiro Jo [15]. By viewing each bubble as living material that grows and interacts, and seeing each pore on the airstone as a “pixel,” it can be seen how the interactions between the bubbles mirror the spontaneity and unpredictability found in Living Images.

The morphology of a slime sculpture is a direct result of the collective behaviors of its constituent bubbles. Through these behaviors, the sculpture undergoes constant transformations, embodying a living, evolving form continuously shaped and reshaped by the underlying interactions of its bubbles until the cycle of the sculpture ends.

Creating a slime sculpture involves two systems for generating and shaping slime bubbles (Fig. 4a). The pneumatic system, linked to an airstone via a valve and an air compressor, creates the bubbles. The amount of air supplied initiates the bubbles’ spontaneous interactions, which lead to the body of a slime sculpture. Meanwhile, an elevating system, connecting a high-torque stepper motor with airstone supports, allows for precise control over the airstone’s movements. By controlling the elevating system, we can move the airstone at specific speeds and directions, simultaneously distorting the slime and bubbles.

To orchestrate both systems, we used TouchDesigner, a node-based visual programming language, for precise control over the systems. Here’s a step-by-step demonstration for creating a specific slime sculpture (Fig. 4b): Parameters like motor steps, heights, directions, and valve angles are put into TouchDesigner. The elevating system lifts the airstone, moving 45,000 steps in 11.4 seconds, allowing slime to thinly coat it. Simultaneously, the valve opens to a 37° angle in 3 seconds, letting compressed air from the compressor flow through the hose and airstone into the slime layer, forming bubbles. These bubbles collectively shape the sculpture as the airstone continues to rise to the designated height. Finally, the valve closes, and the airstone descends, marking the end of one sculpture cycle.

The example above demonstrates how a certain set of parameters influences the shaping of a slime sculpture. During explorations, we identified six primary shaping outcomes, which were formed from different parameter settings. We refer to these as sculpting methods, which were named based on the observable physical descriptors they produce during formations. These methods utilize the characteristics of NNF, enabling us to “sculpt” slime into diverse forms. Categorizing and naming different parameter settings allowed us to envision the transformations of the body of a sculpture, facilitating effective communication among ourselves. For instance, instead of discussing every parameter’s value each time, we can simply say: “Let’s do the Stretch first and then go Expand for a while.” Below, we introduce the six sculpting methods for slime sculptures.

• Stretch: The elevating system gently raises the airstone, lifting a layer of slime attached to it. At this speed, the slime behaves like a liquid with high stretchability. Consequently, as the airstone ascends, the entire body of slime stretches into an arched shape (Fig. 5a).

• Separate: The airstone ascends rapidly, causing slime and slime bubbles around the airstone to detach from the rest of the slime. At this moment, due to its NNF properties, the slime behaves more like a solid with less stretchability, resulting in separation (Fig. 5b).

• Expand: The valve is adjusted to open slightly for a predetermined duration, allowing the bubbles to expand to a specific size (Fig. 5c).

• Roar: The valve opens at a wide angle for a set duration. This action usually ruptures the bubbles and produces sounds by forming air tunnels through the solid-like slime (Fig. 5d).

• Elongate: When the bubbles adhere to the slime’s surface within the container, lifting the airstone at this moment stretches the bubbles, elongating the form of the sculpture (Fig. 5e).

• Compress: After the formation of large bubbles, the elevating system quickly lowers the airstone. This causes the bubbles to press against the slime’s surface in the container, deforming the sculpture (Fig. 5f).

There is no set order for using these methods. For example, we simultaneously used the Expand and Elongate methods to create the sculpture in Fig. 4b. It’s important to note that, for each method, the value of each parameter in the setting is not a fixed number but within specific ranges. For example, with the Elongate method, adjusting the height parameter to a higher value will cause the elongated bubbles to take on more almond-like shapes.

We experimented with different parameter settings across various sculpting methods. Figure 6 illustrates five distinct types, each made by several methods combined and performed four times. Due to the spontaneous behaviors of bubbles, each formation was different even when using the same methods with the same parameter setting. Nonetheless, when comparing the different types, clear distinctions emerge: The overall contours of the sculptures within each type exhibit consistent patterns. Take type Little Tree as an example. Despite each Little Tree formation’s uniqueness, they all consist of two basic forms—a cylinder and a multisphere structure—that together mirror the fundamental parts of a tree: its trunk and crown, hence the name.

In 2022, our slime sculptures, called Emils, were first shown publicly at Soft Resilience, an exhibition in Taiwan [16]. Each sculpture was enhanced by a range of projected colored lights.

We chose white light to highlight the collective movements of bubbles, while the other colors were used to explore their impact on viewers’ perception of the sculptures. Different types of sculptures were showcased one after another. Each slime sculpture ended as the airstone lowered back into the container, followed by a short pause for the liquid-like slime to refill the space before the next sculpture began. During the exhibition, we gathered audience feedback and insights, which we have categorized and discuss further below.

The behaviors of slime bubbles reminded some viewers of the cycle of life. One viewer recounted a similar experience while watching a mushroom grow in a time-lapse video. This story resonated deeply with our inspiration from multicellular organisms. Observing such changes in real time with mushrooms, plants, or humans is impractical, as cellular birth and death occur constantly yet subtly. Alternatively, slime sculptures act as a tangible, accelerated representation of life’s journey from birth to death.

When experimenting with the projector, we accidentally cast the image of a face onto expanding bubbles (Color Image Ca). The effect was so striking that, when we touched it, it seemed as though there was a tumor growing aggressively beneath a real face. This unexpected visual and tactile experience led us to realize the potential of colored projection. While realistic contents offer powerful visual impacts, we found that even simple colors could also be compelling. Moreover, compared to realistic content, simple colors allow the audience to focus on the sculptures’ forms, not the content projected.

In the exhibition, we found that simple color arrangements indeed strongly influenced the audience’s perceptions of the sculptures. For instance, a sculpture with red light projected upon it reminded some viewers of flesh and organs (Color Image Cb). Even without visual content, people still perceived the dominant bubble as a growing tumor popping out from the organ. Furthermore, certain colors reminded viewers of specific objects. For example, many Taiwanese audiences associated the gradient green sculpture (Color Image Cc) with Jadeite Cabbage, stored in the National Palace Museum in Taipei (Color Image Cd).

Some visitors commented on the texture of the slime sculptures. One visitor mentioned that it reminded him of muscle fibers partially covered with skin. Another visitor said the long threads of slime clinging to the surfaces of the slime bubbles evoked for her images of tree trunks entwined with the aerial roots of banyan trees. Before visiting the exhibition, many assumed slime would be smooth and reflective; they were surprised by the complexity of the sculptures’ texture. This complexity was due to the NNF characteristic. When bubbles ruptured, the remnants of the ruptured bubble fell onto the slime below. As this happened rapidly, the residue retained its shape for a period without blending into the surrounding slime. Consequently, when new slime bubbles grew, these new bubbles with just-ruptured bubble remnants displayed an organic, fiber-like texture.

One unique aspect of slime bubbles was their resilience under manipulation. Visitors could touch, grab, or gently pinch them without causing them to rupture. This feature allowed for a tactile experience. Since the slime bubbles were resilient and did not burst easily, allowing visitors to gently hold the expanding bubbles offered them a unique tactile experience. Some participants experienced the sensation of muscle-like bodies expanding against their palms, evoking the imagery of an inhaling organ inflating to suck in more air.

Another way to experience the sculptures was by pinching the bubbles. Unlike soap bubbles, the audience could actually feel a slime bubble’s thick wall when they pinched one. Sometimes they squeezed too hard or too fast and tore parts of the bubbles. But unlike rubber balloons, the slime bubbles didn’t pop instantly. Instead, they slowly deflated as air escaped from the tear. “It becomes a piece of skin!” exclaimed one visitor, holding a flattened part of a slime bubble, making a vivid comparison to human skin as the “skin” slowly melted and dripped back into the slime container.

Some visitors noted the distinct auditory experiences produced by certain sculptures, describing the sounds as unlike anything they had typically encountered. They compared the sounds to those that could be made by animals, yet not by any familiar one. The sounds were particularly noticeable during the Roar process, where air was largely escaping the slime. Owing to the slime’s NNF nature, the high-speed air creates an air tunnel through the slime. As airflow persists, the slime’s solid-like properties prevent the tunnel from closing, making the slime resemble an animal’s vocal tract, producing unexpected sounds.

The sensory experiences of vision, touch, and sound were not isolated occurrences. Instead, they became a holistic experience for the audience. Various groups of slime sculptures emerged sequentially from the container, demonstrating the diverse possibilities slime sculpture art could offer.

In preparation for the Ars Electronica festival (Fig. 7), we made several adjustments to Emils. Firstly, we adjusted the proportion of ingredients to account for Austria’s colder and drier climate, which initially resulted in stiffer slime less conducive to bubble formation than in our experience in Taiwan. We incorporated stickier wood glue and fine-tuned the amount of glycerin to enhance the slime’s suitability for bubble creation.

The previous exhibition aimed to explore the potential forms and sensory experiences that could be achieved with slime sculptures. For the second exhibition, our objective shifted towards integrating various types of slime sculptures into a cohesive performance. To realize this vision, we made several enhancements. Below, we outline these changes and share the feedback received from the audience.

At our first exhibition, while visitors were fascinated by the formations of the slime sculptures, some highlighted a de tail we had missed: the airstone’s abrupt stop at its target, which created an unnatural jolt that disrupted the illusion of life. Taking this feedback into account, we smoothed the airstone’s movements for a more natural transition. The airstone was adjusted to decelerate upon approaching its destination, followed by a soft, rhythmic pulsation, emulating the subtle motions of living entities, which never remain perfectly still. These adjustments have brought a more lifelike quality to the sculptures, enriching the immersive experience.

We were fortunate to display our work in a tunnel that significantly amplified the sound effects of Emils. Building on our prior experiences and audiences’ feedback, we paid closer attention to the sound effects this time. We observed that stiffer slime produced a higher pitch, resembling a “moaning” sound. To further explore this auditory dimension, we introduced another type of slime sculpture. In this variant, only the Roar method was performed for a long duration without moving the airstone. This performance resulted in the formation of air tunnels that were longer and wider than those in our first exhibition. Meanwhile, one of our team members kept breaking bubbles and slowly stirred the slime to manipulate the width of the air tunnel. This intervention altered the pitch and the rhythm of the sound, enriching the auditory experience [17].

The ephemeral nature of slime bubbles offers an intriguing canvas for exploration—each sculpture is a unique manifestation, even under similar conditions. Therefore, we wanted to document the formation of slime sculptures in real time. To achieve this, we installed a Microsoft Kinect Azure depth sensor adjacent to the sculpture. At the designated moment, TouchDesigner triggers the sensor to conduct a scan, employing depth filters to remove any unwanted background elements. The resulting digitized snapshots were recorded and turned into a gallery of animated 3D models, which were then projected onto a wall, inviting the audience to observe the myriad vibrant forms. Throughout the exhibition, we archived a collection of 2,078 point cloud files accompanied by corresponding color images. This data can be converted into 3D mesh data, serving as a creative resource for computer-generated animation or physical sculpting using digital fabrication techniques.

This paper presents slime, commonly known as a children’s toy, as an innovative medium for art. It focuses on utilizing slime bubbles’ collective behaviors to create various ephemeral kinetic sculptures. We highlight the importance of understanding slime’s NNF properties for artistic manipulation, which allows for the alteration of form and production of sound. Our exploration details the interactions among slime bubbles that contribute to the sculptures’ dynamic nature. Additionally, we describe how we “sculpt” a series of slime sculptures by manipulating parameter sets in pneumatic and elevating systems. We also share the audience’s sensory experiences at the exhibitions we participated in.

There are numerous potential developments for slime sculptures, including altering the airstone’s structure to affect bubble formations and extending airstone movements beyond mere vertical shifts. Nonetheless, the fundamental concept remains: using slime bubbles’ collective behaviors to shape the sculptures’ bodies. Within this framework, slime sculptures resemble living organisms, with the systems’ parameters mirroring genes, and the slime bubbles acting as cells. As creators, our only role is to set the initial parameters—much like setting genetic foundations—that guide each sculpture’s development, and the ultimate details of each sculpture are left for slime bubbles themselves to define.

This project was supported by the National Science and Technology Council, Taiwan.