Introduction

Living in a society where agriculture acts as the world's main source of food production while contributing to environmental sustainability and the economy, agricultural technology is bound to advance. Stemming from the dawn of human civilization, the prominence of agriculture persists.

Despite the advancement of agricultural technology throughout the years, some flaws remain regarding the innovation of farming tools, particularly mechanical seed drills. Primarily driven through fossil fuels, mechanical seed drills efficiently plant seeds throughout open and fertile soil, typically enhancing crop uniformity, by ensuring precise seed placement and depth control.

Although the efficiency and precision of mechanical seed drills have significantly impacted agricultural productivity, concerns persist regarding their environmental implications, cost efficiency, and transportation in less economically developed areas. Hence why I felt the need to contribute to the development of agricultural tools by designing a handheld mechanism for a versatile seed dispenser concept, requiring the need of a seed capsule encasing the seeds whilst being biodegradable.

Preliminary Research

The exploration of plastic degradation methods was necessary for the purpose of searching for suitable materials for the seed capsules/projectiles. When doing so, utilizing 3D printing seemed like a viable solution to produce the seed capsules, due to the efficiency and precision that 3D printing offers. However, given that most 3D printing filaments are plastics, the emphasis then shifts towards the utilization of ethylene glycol and hydrotalcite as a means to accelerate the degradation of the seed capsules. 

An experiment delving into the effects of ethylene glycol and hydrotalcite conducted by Vivek Sharma & Priyanka Shrivastava demonstrated drastic results regarding PET degradation, resulting in the decision to test the substance's effects on common 3D printable filament, particularly TPU, and PLA. As mentioned, the 3D designing software Fusion360, was used to bring the agricultural innovation to life, modeling the frame of the seed dispenser designs. In addition to this, Arduino fundamentals and programming were also needed to develop the electronic components of the seed dispenser, ensuring accurate deployment and functionality in the field.

Result

SERVO DRIVEN SEED DISPENSER PROTOTYPE AND CONCEPT.

The parts:

• 3 servo brackets

• 3 arms

• 3 servos 

The design includes a curved tube that guides the seed capsules under the nozzle of the dispenser follwed by 2 servo mounts that regulate the dispensing of the bullets. The handle accomodates 2 switches, the first switch is to activating the first servo to open and close so as the second switch performing the same action. A thin layer of TPU acts as a flexible nozzle that keeps the capsules in place once dropped from the reloading servo and through the curved tube. 

PNEUMATIC DRIVEN SEED DISPENSER AND CONCEPT.

The pneumatic seed dispenser consists several primary components, which are:

• Diagonal split bracket : accomodates all the internal of the dispenser, prioritizing the pneumatic piston and the solenoid valve. 

• 2 pistons

• 1 magazine : to store the seed capsules

• 2 servo brackets

• Switches

• Air tank

SEED DELIVERY METHOD

For seed delivery, seeds are placed in cartridges that are filled with soil according to the intended landscape. The point of focus is the material and design of the delivery cartridge. It has to have several key characteristics, which include:

• Needs to biodegradable within <1 month to ensure germination

• Products of the degradation are not garmful to the surrounding environment 

• Lightweight

• High tensile and compressive strength that can withstand being shot out

• Economically viable

• Easy to manufacture

• Has to have a mesh like exterior that facilitates root establishment while reducing the needed plastic for degradation.

Then, a filament made from TPU and PLA were chosen due to their availability.

Analysis

To determine the overall degradation of TPU and PLA, a UV-VIS analysis of the remaining extracted solution was performed. Several observations were seen within the 2 graphs. As seen in graph, 1 absorbance values were relatively linear with one observable peak at the 900-1000 nm range. On the other hand, graph 2 has one observable peak at the 500 nM range. Previous literature has stated that TPU has a peak absorbance at 500 M while the peak absorbance of PLA is around the 580nM. The lacking yet inconclusive data presented in the first graph does not display signs of degradation when soaked in ethylene glycol however, the filtrated PLA has traces of PLA detected around the 500 M range suggesting that the PLA has degraded in the form of the solution, indicating signs of degradations. Henceforth, PLA is a viable option for plantation where we can pretreat the capsules to accelerate natural biodegradation in soil conditions after deployment. Other methods such as elevated UV and thermal conditions to pre degrade PLA may be plausible.

Conclusion and Future Exploration

Several conclusions can be deduced from this research:

- Pneumatic systems are superior to servo-based systems for high speed projectile mechanisms due to the speed, capacity and low maintenance when opposed to servo-based

- PLA may be suitable for rapid biodegradable applications after oxidative degradation via magnesium hydroxide. More test is needed to verify this.

- TPU is not suitable as it cannot be even pre degraded

- Field testing of pre degraded PLA is necessary to quantify further the optimal pre degradation condition. Ideally, one would tune the pre degradation amount to still allow for sufficient strength of the material while also making sure that it can be degraded microbially in soil within several months.

Future suggestions:

- More biodegradable substances such as paper mache can be utilized for seed delivery mechanisms.

- Delivery systems can be optimized using machine learning to ensure proper payload delivery.