openPOT: Interactive Plant Operating Terminal
Plants are inexpressive creatures comparing to animals. This makes it hard for people to understand their growth state and perceive their subtle growing process. Most research for presenting the plant growth is functionality oriented, however, only a few focuses on plant aesthetic due to the difficulties of transforming subtle plant growth and diversified plant aesthetics into a more tangible form.
In this paper, we proposed the openPOT (plant operating terminal), an independent smart-pot interface, to physically augment the communication between plants and their owners, and to enhance people’s perception of plant aesthetic. The openPOT senses three basic elements of plant growth and interprets them into dynamic forms with biological nature. Inspired by the sensitivity and defense mechanism of special species, we introduced nervousness or excitement into the openPOT system, making it more responsive to people’s interaction. In this paper, we describe stakeholder, interaction framework, computing algorithm, structure design, and evaluation methods of long-term user diary kit studies.
Figure 1. Participant interacts with the openPOT system
Since the early age, plants play an important role in people’s daily life. People grow indoor plants to decorate a room and purify the air. They feel physiological positive and calming effect from the physical appearance of plants. Moreover, they become intoxicated to the spiritual and aesthetic enjoyment provided by plants.
However, comparing to animals, plants are inexpressive creatures. To the human, most species of plants are silent and motionless despite their long-term growth. It’s not only hard for most of us to understand plants’ growth state, but also hard to perceive their subtle growing process in a short time period. Also, most species of plants show limited awareness and provides hardly any feedback to people’s presence and interaction.
Due to this relative inexpressive and non-responding characters, plants get ignored easily by their owners as well as others. While people cannot leave fascinating smart devices for a single day, they can easily put plants aside for weeks and let plants alone and eventually dead of wilt.
Thus, we designed the openPOT (plant operating terminal), an independent smart-pot interface. The openPOT intends to physically augment the communication between plants and their owners, enhance people’s perception of plant aesthetic, and improve the relationship between the human being and nature.
Various research has been done for presenting the plant growth. These works can be mainly categorized into two different directions: functionality oriented and aesthetic oriented. The functionality oriented plant technology focuses on monitoring the living environment to enhance the health of plants. Many plug-in products have been made to sense the soil environment and represent the data in a visual or audio form directly or through WIFI connection. They can be used to automatically control the watering process of plant and make the growing of plant effortless.
On the other hand, there are aesthetically oriented plant technologies focusing on "designing highly expressive interactive plants".  However, the related works in this direction are comparatively few due to the difficulties of transforming this subtle plant growth and diversified plant aesthetic into a more direct form. One research has been made using computer graphic to simulate both living and artificial plants depending on user’s interaction. The other research focused on designing plant pots which use light and sound output as feedback.
These research either require additional screen displacement for advanced virtual graphics or depend on limited forms of visual output. We want to design a light-weighted smart pot interface while keeping the output physical and biomimetic. Instead of using pixels and sound waves and dive deep into the virtual world, the openPOT depends on other forms of output to maintain plants’ "retro style". Thus, this dilemma was approached by designing a shape-changing-skin of the pot.
The openPOT system intends to serve general plant owners and plant lovers. Through enhancing plant communication, the system helps plants gain more attention, care, and appreciation from people. Besides, we hope that the openPOT system can help developing a closer relationship with nature for children and those who used to be limited to the artificial world.
The openPOT system senses three basic yet crucial elements of plant growth: light, temperature, and humidity. Besides, the changes of light input can also be functioned as people’s interaction. Based on these data input, the openPOT system interprets them into a dynamic and tangible form with a biological nature. We were inspired by the sensitivity and defense mechanism of two special species: mimosa pudica (also called sensitive plant) (Figure 2.A) and tetraodontidae (also called pufferfish) (Figure 2. B). Mimosa pudica is an herb known for its sensitivity: the compound leaves fold inward and droop when contacted with other objects, defending themselves from harm. These leaves will re-open a few minutes later.  A pufferfish expands itself into a spiky, large sphere  when it feels danger in the environment. Thus, we would like to apply a degree of sensitivity which can be perceived as nervousness or excitement into the openPOT system. Depending on the level of nervousness or excitement, the openPOT will provide corresponding visual feedback in shape changes and light frequency. When the plant is not interacted with, the motion of openPOT will be kept at a natural breathing rate similar to human being.
Figure 2. A) Mimosa Pudica B) Pufferfish
Figure 3. Interaction Framework
Figure 3 shows the interaction framework we propose. The openPOT interface detects the light, temperature, and soil humidity input from plants and light changes input from a user using built-in sensors. Simultaneously, the interface changes the surface shape and motion with an actuator and the LED lights change the color and frequency according to a real-time data computing. This visual and dynamic transformation is provided to users as interaction feedback.
Physical Computing Algorithm
Figure 4. Physical Computing Algorithm
To make the openPOT be responsive to the environment, we employed multiple sensors and an Arduino micro-controller to sample the environment in real time. Data will be collected in terms of temperature, brightness, and humidity. To characterize the openPOT system, we introduced an attribute, nervousness, to change the status of the system. Since the brightness is the most significant variable when a user is approaching the system, we adopted it as the source of nervousness. Originally, we set nervousness in proportion to the environmental brightness, which was sampled by four photo sensors mounted on the top of the system. The formula for nervousness is shown as the following. Kn is a coefficient of nervousness.
nervousness = Kn * brightness
However, the system's nervousness was found to be seriously affected in extreme situations. For example, when the system was placed in a dimmed room, it rarely responded to the movements nearby. Since the derivative of the brightness remained active regardless of the environmental brightness level, it turned out to be a better source of nervousness. After adopting derivative, the formula for nervousness became the following. Kn is a coefficient of nervousness.
nervousness = Kn * derivative of brightness
In addition to the nervousness, we extended it to another variable, breathing frequency, which brings more sense of creature into the system. The formula for the breathing frequency is shown as the following. Kbf is a coefficient of breathing frequency.
breathing frequency = Kbf * nervousness
The breathing frequency was applied in activities such as the periodic motion of the skin and the blinks of the internal RGB LED array. Temperature information is used to control the color of the RGB LED array, which gives users a better sense of the living environment of plants. When the environment temperature is higher than the appropriate temperature, the LEDs will emit warm-toned light. If the environment temperature is too low, the LEDs will give out cool-color light. The red, green and blue components were defined as the following:
R = 255
G = (default room temperature - temperature) * 15 + 30
B = (default room temperature - temperature) * 10 + 0
The data from the humidity sensor was mapped to the position offset of the skin movement, which was controlled by the rotation of a servo motor. Khmd is a coefficient of humidity sensor data.
skin position offset = Khmd * humidity
Finally, the skin position offset and the periodic motion of the skin were implemented by rotating a servomotor, which is attached to each piece of the skin through strings. The servomotor rotation is defined as the following:
servomotor rotation =
skin position offset + skin swing amplitude*(sin (system time * breathing frequency) +1);
Figure 5. A) One Skin Piece’s Connection Details B) RGB LED’s Color Scheme
Figure 6. A) Internal Structure B) External Structure
Figure 6.A demonstrates the three-layers internal structure of the openPOT. The top floor is the sensor layer which contains four photo sensors, a temperature sensor, and a humidity sensor. This layer was covered with natural materials such as wood pieces and stones to maintain a natural aesthetic. The second floor is the plant pot layer which contains an independent plug-in plant pot. The ground floor is the circuit and actuator layer which contains an Arduino Pro mini board, a breadboard, a voltage regulator, and a severe motor. This floor includes the core part of the openPOT system: Data obtained from sensors are sent here to be processed and controlled signals are sent to actuators.
Figure 6.B shows a prototype of the openPOT’s external structure. We choose the geometric shapes such as cubes, triangles, and lines to enhance a tension between the artificial craft and organic creature behavior. Although the openPOT serves as an extension of the plant and exaggerate the plant’s behavior, we don’t want to hinder users from enjoying the plant itself. Instead, we hope users can be encouraged to pay more attention to the real plants through the openPOT system.
Due to the inaccuracy of manual manufacturing, the openPOT prototype is still away from the ideal design. In the future, we hope to refine the skin structure by adding more identical geometric shape pieces. The shape of the pieces can be further designed and related to different type of plants.
The evaluation process of the openPOT project hasn’t been completed by the time. Here is what we proposed for the evaluation methods which will consist of two parts: the public installation video observation and long term user diary studies.
Public installation video observation
The openPOT system will be displayed as a public installation. The public will be encouraged to interact with the system and write down words or phrases to describe their associated thoughts or feelings about the system. These association tags will later be collected and used for individual user studies. The event will be documented through a video format. The public installation enables the openPOT to face a lot of users simultaneously which can test the stability of its behavior in an extreme situation. Also, we hope the installation can arouse public curiosity, concern, and reflection about nature plants.
Long-term real-life user studies with diary kit
As plant growth is a subtle long-term process, it won’t be very meaningful for us to use common evaluation methods such as survey or observational test in a lab setting. Instead, a real-life context and a time period are crucial to evaluate this system qualitatively. Thus, long-term real-life user studies will be carried out to get a better contextual understanding of user’s behavior and experience. Selected users will be asked to raise a plant using the openPOT system for 14 days. Meanwhile, they will be provided with a diary kit including an instruction diary booklet, 3 postcards, and a calendar. Preliminary tasks will be set at the beginning of the studies to form habits of the openPOT system. Users are going to document their daily experience with the system on the diary following the instructions. The postcards are pre-stamped and will be used as phased reflection questions about user’s behavior and attitude changes in a more general scope about plant and nature. Users are instructed to send back the postcard separately. The calendar will be used as a reminder as well as a task checklist.
Figure 7. Diary Booklet Design
Figure 7 shows the design of the diary booklet. In the first part, we will state the purpose and explain instructions of documentation. The basic user information will be collected in this part. In the second part, we will provide preliminary tasks to users in order to form habits of interacting with plants. The third part is the core part of the diary, which encourages users to document their daily experience with the openPOT according to the instructional questions. The last part serves as an overall reflection about the experience and some future assessment.
 Poupyrev, I. et al. Botanicus Interacticus: interactive plants technology. SIGGRAPH '12 Emerging Technologies. ACM (2012), Article 4.
 Mimosa Pudica https://en.wikipedia.org/wiki/Mimosa_pudica
 Pufferfish (family Tetraodontidae)
 Plants Remember You if You Mess with Them Enough March 28, 2016 http://www.nytimes.com/2016/03/29/science/29obs-plants.html