Opportunity

We began by researching plant species suitable for space cultivation and found that algae are particularly well-suited. They are rich in protein and essential nutrients, require no soil, produce no waste, and are relatively easy to grow.

However, cultivating algae on a space station poses challenges, mainly due to microgravity. Traditional water-based cultivation doesn't function properly in microgravity, and harvesting or processing algae becomes complicated as the biomass tends to float and disperse.

Proposed Solution

To address these challenges, we proposed a new solution: instead of traditional water-based cultivation, we use hydrogel as a solid growing medium. Hydrogel can provide water and nutrients to plants, has been proven suitable for algae cultivation, and is 3D printable.

Specifically, we chose sodium alginate hydrogel—a food-safe material rich in dietary fiber. Thanks to its edible nature, the grown algae can be consumed together with the hydrogel, eliminating the need for separation or post-processing. This makes it ideal for food 3D printing and significantly simplifies the cultivation and harvesting process, making it more suitable for the space station environment.

The overall system follows four steps: 3D print the sodium alginate structure for cultivation - Place the printed structure into the bioreactor - Allow algae to grow on the cultivation rack - 3D print the algae-based food

Design Overview

The system consists of three main part: a 3D printer, a bioreactor, and a growth rack.

The Printer

The 3D printer in the system is used both to print the sodium alginate cultivation structures and the final food products.

Its architecture from top to bottom includes the printing tank interface, extrusion head (X/Y axes), printing platform (Z axis), and base with an interactive screen. The printer moves along three axes, as shown in the video. It measures approximately 354mm × 354mm × 548mm, with a build volume of a 250mm diameter by 200mm tall cylinder.

Interaction & Details

The bottom part of the printer features a touchscreen for user interaction, along with two physical buttons. A handle on the side makes it easier for astronauts to operate in the space station's microgravity environment.

On top is the printing material tank interface, where the tank locks in place with a twist after insertion. The printer feeds material using a vacuum suction system. Each interface has a corresponding number label and status indicator light.

Structure Printing

The first step in the system operation is to print the sodium alginate structure for algae cultivation. Sodium alginate solution quickly forms a hydrogel when combined with Ca²⁺ solution. To achieve this, we designed separate tanks for sodium alginate and calcium solutions that mix in the extrusion head, allowing rapid gelation and solidification during printing. This also solves the adhesion issues of printing materials in microgravity.

The printing platform is detachable and serves as the base for the bioreactor. The resulting cultivation structure, shown in Figure 3, maximizes surface area to improve growing efficiency.

Installation Structure

The printed structure, along with the printing platform, is installed into the outer shell to form the complete capsule.

Capsule Design

The capsule consists mainly of a base and an outer shell. Inside, it houses the sodium alginate hydrogel structure. The shell is made of transparent material and features a gas exchange vent on top to allow algae to absorb CO₂ and produce oxygen. The base includes a mounting mechanism and a central port connecting to the interior.

The tank measures approximately 100mm in diameter and 300mm in height, with an internal volume of about 1.3 liters.

Cultivation Chamber Design

We also designed a cultivation chamber where the capsuleis inserted for algae growth. The chamber features indicator lights around its exterior to show status. Inside, a UV lamp provides the necessary light for algae growth, surrounded by mirrors to maximize light efficiency. Algae grow on the structure as shown in the last pic.

Growing Rack

The cultivation chamber features a modular design and can be stacked into arrays up to 950mm tall. A touchscreen in the center allows for interaction and status monitoring. Its size matches the European Columbus module’s rack dimensions, fitting perfectly into a single rack space.

Food 3D Printing

Once the algae have grown, the bioreactor is placed onto the printer to 3D print food using the hydrogel-algae mixture, as shown in the example. Food 3D printing can help reduce the monotony of astronauts' diets. Research by Nendo shows that different chocolate structures offer distinct textures, and the customization enabled by 3D printing opens up more possibilities for food experiences.