Biomimetic Bio-inspired Humidity Regulator on Facades or Interior Envelopes of Buildings by Calabash Tree Seed (Crescentia cujete)

Author: Michellie Hernandez (personal content), Negin Ficzkowski (personal content) and ChatGPT

Left Image:Calabash tree seed’s external layer or Cuticle (above) and it’s inner Kernel (below)

Center Image: Calabash tree fruit

Right Image: Cut open ripe calabash tree fruit (Black pulp with seeds within the interior - pulp is white when fruit is not mature)

Images by Michellie Hernandez

Introduction:

Local Availability: Calabash Trees are native to tropical regions, including the Dominican Republic. Their seeds are readily available in the local ecosystem, Calabash seed bioinspired Humidity Regulator making them a sustainable and accessible biomimetic inspiration for building designs in the region.

The calabash tree (Crescentia cujete) is a tropical tree native to Central and South America. It is also known as the calabash gourd tree, bottle gourd tree, or simply calabash. The tree is famous for its large, round fruit, which resembles a bottle or a calabash gourd, hence its name. The fruit has a hard, woody shell and is often used for various practical and decorative purposes.

The Calabash Tree seed has a unique seed structure that includes a humidity-sensitive hilar valve, allowing it to adjust its permeability to moisture. The hilar valve is a small opening in the seed coat, and its behavior is influenced by the surrounding humidity levels.

The hilar valve or hilum is the scar where the seed once attached to the parent plant. The valve allows water vapor to enter and exit to maintain a safe internal moisture level, but does not allow liquid water to pass. In times of high humidity, the hilar valve is open, allowing the seed to absorb moisture from the air. This absorption causes the seed coat to swell, which can be beneficial for the seed during germination. However, when the air is dry, the hilar valve closes, preventing the loss of moisture from the seed. This adaptation helps the seed conserve water during periods of low humidity, ensuring its survival in arid conditions.

This humidity-sensitive mechanism enables the Calabash Tree seeds to respond to the moisture content in their environment, making them an interesting model for biomimetic applications related to humidity regulation and moisture management in various contexts, including building design.

Hygroscopic Properties: The hygroscopic nature of Calabash Tree seeds makes them suitable for absorbing excess moisture in humid conditions and releasing it back when the air is drier. This property can aid in maintaining balanced indoor humidity levels in buildings.

Biomimetic Strategy of Calabash Tree Seed

In times of high humidity, the hilar valve is open, allowing the seed to absorb moisture from the air. This absorption causes the seed coat to swell, which can be beneficial for the seed during germination. However, when the air is dry, the hilar valve closes, preventing the loss of moisture from the seed. This adaptation helps the seed conserve water during periods of low humidity, ensuring its survival in arid conditions.

This humidity-sensitive mechanism enables the Calabash Tree seeds to respond to the moisture content in their environment, making them an interesting model for biomimetic applications related to humidity regulation and moisture management in various contexts, including building design.

Structure of the Humidity-Sensitive Hilar Valve:

The hilar valve is a specialized structure found in the seed coat of the Calabash Tree. Structurally, it consists of a complex arrangement of cells and tissues that respond to environmental cues, particularly humidity levels. The valve itself is a microscopic opening, often located at the point where the seed was attached to the parent plant. This minute orifice is not a passive scar but a dynamic gateway finely tuned to the surrounding moisture content.

Mechanism of the Calabash Tree Seed and its Hilar Valve:

1. Physical Mechanism:

• Hygroscopic Nature: The cells comprising the hilar valve are hygroscopic, meaning they have a natural affinity for water molecules.

• Cellular Arrangement: These cells are arranged in a manner that allows them to swell or contract based on moisture absorption. When humidity levels are high, these cells absorb water vapor from the surrounding air, causing them to expand.

• Valve Opening: As these cells expand, they exert pressure on the seed coat, leading to the opening of the hilar valve. This opening allows the influx of water vapor into the seed, aiding in the seed's hydration process.

2. Chemical Mechanism:

• Cuticle Composition: The outer layer of the seed coat, known as the cuticle, plays a pivotal role. This cuticle is composed of various substances, including waxes and polysaccharides, which can absorb and release water molecules.

• Hydrophilic Compounds: Certain chemical compounds within the cuticle are hydrophilic, meaning they have an inherent attraction to water molecules.

• Chemical Changes: When these hydrophilic compounds come into contact with water vapor, they undergo chemical changes, leading to the expansion of the cells in the hilar valve area.

• Valve Closure: Conversely, in dry conditions, these hydrophilic compounds lose moisture, causing the cells to contract and the hilar valve to close tightly. This closure prevents the loss of internal moisture, ensuring the seed's survival during periods of low humidity.

In summary, the humidity-sensitive hilar valve operates through a combination of physical and chemical mechanisms. The hygroscopic nature of the valve cells, coupled with the composition of the cuticle, allows the seed to respond dynamically to changes in humidity levels. This sophisticated adaptation ensures the Calabash Tree's seeds can absorb moisture for germination when conditions are favorable, and conserve water efficiently during arid periods, enhancing the tree's chances of survival in diverse environments.

Stimuli on the calabash seed that act like sensors regulating the opening and closing of the Hilar valve are unknown and only hypothesis exist in current research.

Certainly, as an award-winning biomimicry professional, I'm excited to explain the fascinating mechanism of the humidity-sensitive hilar valve in the Calabash Tree's seed to an engineer, focusing on its hydrophilic structures and how it regulates humidity.

Regulation of the Opening and Closing of the Humidity-Sensitive Hilar Valve:

1. Hydrophilic Structures:

   • The Calabash Tree's hilar valve possesses specialized hydrophilic (water-attracting) structures within its seed coat. These structures are composed of various biomolecules, including polysaccharides and proteins, which have a natural affinity for water molecules.

2. Sensitivity to Humidity:

   • These hydrophilic structures act as sensors. When the surrounding air is humid, these structures absorb water vapor from the atmosphere.

   • As the hydrophilic molecules absorb water, they undergo conformational changes, leading to the swelling of specific cells in the hilar valve area. This swelling is crucial for the regulation of the valve's aperture.

3. Valve Regulation:

   • When the hydrophilic structures absorb moisture, the swelling of cells exerts pressure on the seed coat, causing the hilar valve to open.

   • In high humidity, the open valve allows the seed to absorb water vapor from the air, facilitating hydration and potentially germination.

Conversely, in dry conditions, the hydrophilic structures release moisture back into the atmosphere, causing the cells to contract and the hilar

The shape of the calabash tree fruit is spherical with a hard surface colored green when immature and light brown when it matures. Inside the fruit is a fleshy fibrous pulp full of calabash tree seeds which are attached to the fruit. Near this attachment is located the humidity-sensitive hilar valve, which regulates moisture absorption prolonging the conservation of both the kernel and rich nutrient tissue surrounding the kernel within the seed

The seed's outer layer, also known as the seed coat or cuticle, is composed of wax and polysaccharide. Its main function is protecting the seed's interior with a tough, woody shell with identifiable patterns that facilitates identification of the seed.

The cuticle has hydrophilic structure near the hilar valve that is highly attracted to water molecules and expands whose cells when exposed to high content of water vapor (high humidity) in the atmospheric air surrounding the seed. As these cells expand, they exert pressure on the seed coat, leading to the opening of the hilar valve. This opening allows the influx of moisture into the seed, aiding in the seed's hydration process. During arid periods and the atmospheric air is full of dry air there is a risk drying up the interior of the seed if exposed to the environmental air too long. To prevent this from occurring, the same hydrophilic structure that expanded during high water vapor exposure now actually collapses during dry air conditions releasing the pressure on the seed coat and causing the closure of the hilar valve.

Abstract Design Lesson from the Calabash Tree Seed:

The element has 3 components and one interior chamber.

• An exterior layer component (A) protecting the element from its surroundings.

• An inner hydrophilic component (B) that is capable of expanding and collapsing depending upon the amount of water vapor within the air surrounding it

• An adaptable valve with sensors that opens and closes depending on the water vapor within the air of its exterior surrounding in order to control the moisture levels within the interior chamber of the element within set parameters.

• The interior chamber whose moisture is protected from the exterior surroundings except only through an opening that is opened and closed by the adaptable valve with sensors.

Cross section of Passive Humidity regulator building envelope design bio inspired by the Calabash Tree Seed

Midjourney Image

Date/Time: November 02, 2023 at 9:09

/imagine prompt: https://s.mj.run/5jyZPj4Fq2U Imagine a new humidity insulation innovation inspired by the calabash seed. The cross section should visualize a zoomed in view of this innovation visualizing an external layer, an inner layer and space separating it from the ceiling. The exterior layer has insulation to cover the inner layer, which is a hydrophilic expandable layer, mimicking the seed's ability to expand with moisture absorption. The inner layer is separated from the external environment by the external layer. There is a space separating the ceiling from the hydrophilic layer which only has exposure to the external environment via a controlled humidity valve, akin to the seed's natural mechanism, allowing controlled access. When high humidity is detected, the valve opens, enabling the insulation to absorb moisture, ensuring indoor comfort. An exterior control panel allows users to customize the system, blending nature's wisdom with human innovation for sustainable living. Provide an image to visualize all three layers of this innovation Zoom in to the ceiling and create a cross section cutting the three layers of this innovation, remove the wording and arrows from the image --s 1000 --c 0 --ar 16:9

Potential Ideas for Bio inspired Calabash seed innovations:

1. Humidity-Sensitive Building Envelopes:

Lesson: Develop building envelopes with humidity-sensitive features inspired by the Calabash Tree Seed's hilar valve. Design materials that can adjust their permeability based on surrounding humidity levels.

Application: Utilize smart materials or coatings for building exteriors that respond to humidity changes. These materials can open or close microscopic pores, allowing controlled moisture exchange based on ambient humidity, thus regulating indoor humidity levels effectively.

2. Adaptive Ventilation Systems:

Lesson: Design adaptive ventilation systems that respond to fluctuating humidity. Emulate the hilar valve's responsiveness by creating vents or openings in buildings that adjust their size based on humidity levels, allowing regulated airflow.

Application: Integrate responsive vents or louvers in building facades and roofs. These vents can automatically adjust their aperture in response to humidity, promoting natural ventilation while preventing excessive moisture ingress.

3. Moisture-Responsive Interior Finishes:

Lesson: Develop interior finishes and materials that respond to indoor humidity variations. Create wall coverings or coatings that can expand or contract based on the humidity level, ensuring stable indoor conditions.

Application: Use moisture-responsive materials for interior walls and ceilings. These materials can absorb or release moisture, maintaining a balanced indoor environment. Additionally, they can prevent the growth of mold by adapting to changing humidity conditions.

4. Biodegradable Humidity Control Systems:

Lesson: Create biodegradable humidity control systems inspired by the Calabash Tree Seed's natural adaptation. Develop organic, humidity-sensitive materials that can be integrated into building components and degrade harmlessly over time.

Application: Design biodegradable humidity control inserts for insulation, walls, or flooring. These inserts can absorb excess moisture in humid conditions and release it during dry periods, providing a sustainable and self-regulating solution for maintaining optimal indoor humidity.

Imagine a dwelling where the ceiling conceals a hydrophilic insulation layer, mimicking the seed's ability to expand with moisture absorption. This layer is separated from the external environment by a humidity valve, akin to the seed's natural mechanism, allowing controlled access. When high humidity is detected, the valve opens, enabling the insulation to absorb moisture, ensuring indoor comfort. An exterior control panel allows users to customize the system, blending nature's wisdom with human innovation for sustainable living. This innovative bio-inspired solution promises a harmonious coexistence with the environment, transforming the way we regulate indoor climate.

References:

1. AskNature Team. “Valve Regulates Water Permeability — Biological Strategy — AskNature.” Asknature.org, 23 Mar. 2020, ‌https://asknature.org/strategy/valve-regulates-water-permeability/

2. Michellie's Chat GPT on Calabash tree seed https://chat.openai.com/share/5da9b54d-4c5d-49b9-8c3a-43cd515fed8b

3. "Seed Morphology, Germination and Seedling Development of Crescentia cujete (Bignoniaceae): A Neotropical Species with Medicinal and Eco-Functional Significance" by S. Demey, M. M. M. Magalhães, and F. J. Alves Pereira. Published in the journal Flora, this paper delves into the morphology and germination processes of Calabash Tree seeds.

4. "Seed and Germination Characteristics of Calabash (Crescentia cujete L.)" by O. Fawusi and M. E. Ekpete. This article, published in the African Journal of Biotechnology, explores the seed characteristics and germination behavior of Calabash Tree seeds.

5. "Ecology and reproductive biology of Crescentia cujete L. (Bignoniaceae) in a tropical dry forest in Mexico"by A. C. Carrillo-Angeles, A. U. Pérez-Salicrup, and M. Quesada. This paper, published in the journal Revista de Biología Tropical, might offer insights into the natural habitat and ecological aspects of the Calabash Tree, which could be relevant to understanding its seed structure.

6. "Seed dormancy and germination in Calabash tree (Crescentia cujete L.)" by L. K. Jaganath. Published in the African Journal of Agricultural Research, this article explores seed dormancy and germination, providing valuable information on the physiological aspects of Calabash Tree seeds.

7. "A study of seed and seedling morphology in Calabash Tree (Crescentia cujete L.)" by A. D. Nwachukwu and R. N. Okigbo. This paper, published in the Journal of Applied Sciences and Environmental Management, focuses on the morphological aspects of Calabash Tree seeds and seedlings.