Part 1 If I change the pH level of the environment in which a hydrogel is placed, then it will change the speed at which the contained substance within the hydrogel will diffuse. The hydrogel will diffuse the contained substance because the acidity or alkalinity of the environment will diffuse change the rate of diffusion due to a difference in density between the environment and the substance in the hydrogel.

Part 2 If I increase the concentration of gelatin present in the mixture I used to create my hydrogels, then there will be a lower amount of contained substance in the environment because the higher concentration of a binding component will result in a lower pore size, meaning that it will take longer to release the same amount of dye as a hydrogel with a bigger pore size.

Hydrogels are polymer based structures which can hold and transport fluid substances. These hydrogels have a high amount of water in them, making them have a similar consistency to jelly. Hydrogels can also be manipulated very easily, whether it is through the acidity of the environment it is in, or the concentration of polymer in the hydrogel itself, making them one of the most versatile ways to deliver medical treatment.  Hydrogels are mostly based on diffusion. As we know, all fluid substances have a tendency to travel from areas of higher concentration to lower concentration, and hydrogels are no different. When a substance is placed inside of a hydrogel, it will travel through the pores in the casing to areas of lower concentration, which are most likely outside of the hydrogel. By changing the pore size of the casing, we can manipulate the diffusivity, or amount of time it takes for out solvent to diffuse through our solute. Variables in the hydrogel itself and the environment around the hydrogel can change diffusivity, or the rate at which the solute diffuses through the solvent. I have used acidity as a variable to test the hydrogel because different areas of our body have different ph levels in their environments. By testing a range of different pH levels on almost identical hydrogels, we can study how different parts or areas of the body can react to and manipulate the diffusion of the contained substance. For example, your stomach is noticeably more acidic than your blood, so that variable can affect the rate at which your contained substance is released.

Part 1 Independent:

• pH level of the mixture the hydrogel is submerged in

Dependent:

• Amount of dye that can be diffused in 1 hour

Controlled:

• Concentration of gelatin in hydrogels (10%)
• Amount of dye in each hydrogel (1mL)
• Amount of mixture hydrogel is submerged in (200mL)

Part 2 Independent:

• The concentration of gelatin in my hydrogels (10%,15%,20%)

Dependent:

• Amount of dye that can be diffused in 1 hour

Controlled:

• pH of environment/mixture 
• Amount of dye in each hydrogel (1mL)
• Amount of mixture hydrogel is submerged in (200mL)

Testing effect of ph levels of conditions on drug release rate

1. Heat 90mL of distilled water until it is slightly warm
2. Add 10g of gelatin powder to the water and stir until the solution is clear
3. Pour the gelatin solution into a mold to create 12 identically sized spheres
4. Allow the gelatin to set for 2 hours at room temperature
5. Remove the gelatin spheres from the mold
6. Using a syringe or pipette, fill the sphere with 5ml of blue food dye
7. Allow the hydrogels to sit for 10 minutes
8. Fill four glasses with the following solutions:
   1. Vinegar for an acidic environment
   2. Diluted vinegar for a slightly acidic environment (1 part vinegar for 4 parts water)
   3. Distilled water for a neutral environment
   4. Baking soda for a basic environment (1 gram baking soda for 100mL water)
9. Measure the ph level of each solution and record it
10. Place one hydrogel into each solution and immediately start a stopwatch
    1. Ensure there is constant lighting, and the device used to take pictures remains stable and in the same location throughout the experiment
11. Take photographs at 0,5,15,30,and 60 minutes into the stopwatch
12. After 35 minutes, remove each hydrogel from its solution. Repeat steps 8-11 twice more for a total of 3 trials. 

Testing effect of gelatin concentration of hydrogels on drug release rate

1. Prepare the following 3 solutions
   1. 20% gelatin: 20g of gelatin powder and 80mL of warm water
   2. 10% gelatin: 10g of gelatin powder and 90mL of warm water
   3. 15% gelatin: 15g of gelatin powder and 85mL of warm water
2. Stir each solution until it is clear 
3. Pour each solution into identical spherical molds to create 9 hydrogels of each ph level.
4. Allow the hydrogels to set for 2 hours
5. Remove the hydrogels from the molds, and inject them with 5mL of blue food dye. Allow the hydrogels to rest for 10 minutes
6. Prepare 3 glasses of 100mL distilled water
7. Place one hydrogel into each glass and start the stopwatch
8. Photograph each hydrogel at 0,5,10,15,30,and 60 minutes after starting the stopwatch. 
   1. Remember to keep lighting and camera position constant
9. After 35 minutes, remove the hydrogels from their glasses.
10. Repeat steps 5-9 twice more to complete 3 trials.

Part 1

5 minutes Alkaline: Spread towards point of entry

Neutral and Slightly Acidic: Spread outwards and down from the physical hydrogel

Acidic: Stayed in the immediate vicinity of the hydrogel

15 Minutes Alkaline:  Dye began to diffuse regularly, but dye from source is still going towards point of entry

Neutral and Slightly Acidic: The dye is beginning to diffuse evenly, but only a little bit

Acidic: Dye is still staying in immediate vicinity

30 Minutes Alkaline: Still naturally diffusing

Neutral and Slightly Acidic: Dye is beginning to diffuse more evenly then before

Acidic: Dye is beginning to release outwards and down

60 Minutes Alkaline: Dye has spread all throughout the mixture

Neutral: Dye has spread to the entire mixture, though there is a higher concentration at the bottom

Slightly Acidic: Dye hasn’t diffused in the mixture at all

Acidic: Dye has diffused all throughout, but not evenly

Part 2 5 Minutes 10%: Not much diffusion

15% Not much Diffusion

20%: Not much diffusion

15 Minutes 10%: Light, even dispersion

15%: uneven dispersion, heavy near the bottom

20%: No dispersion, all dye settled at the bottom

30 Minutes 10%: Even dispersion, dye is beginning to set near the bottom

15%:  Uneven dispersion, dye is settling at the bottom still, but not as much as before

20%: Uneven dispersion, dye is still settling heavily near the bottom, but still dispersing a little bit throughout the mixture

60 Minutes 10%: Dye has dispersed throughout the mixture, although some dye has begun to set at the bottom

15% Dye has dispersed throughout the mixture, still heavily settling at the bottom

20%: Dye is lightly dispersed throughout mixture, quite heavily settling at the bottom

Hydrogels are an up and coming breakthrough. This research that I have conducted can help grow more awareness for hydrogels and help guide more research and education on hydrogels and how they work. In the foreseeable future, hydrogels will be used as a primary form of medication for long term diseases and lengthy, low-dosage medication. By studying the different variables which can affect the release we can learn how to prevent and take advantage of these variables in order to individualize and specialize hydrogels from treatment to treatment, and from person to person.

Part 1 From these results, I can conclude that my hypothesis was correct. Changing the pH level of the environment in which I place my hydrogels can alter the rate at which the substance within the hydrogel will diffuse. I can tell this because as we can see both in my graph, and over time in the pictures, the different hydrogels had similar results over all 3 tests, leading me to make the conclusion that my results are accurate and fair.

Part 2 From my results, I can conclude that my hypothesis was correct. The higher the concentration of binding agent present in the mixture used to create hydrogels, the lower the amount of dye released in one hour will be. I can make this assumption based on the fact that in all 3 of my tests, all 3 different hydrogels had quite a bit of dye settling near the bottom, leading me to assume that the dye couldn’t dissolve fast enough and gravity pulled it to the bottom.

This can apply to real life because Hydrogels are the future of medicine. If we can understand how we can manipulate the rate at which they release their contained substance, then it will help us advance their study even further, and help to raise awareness about how they work in the common person

• Small inconsistencies in the shape and size of the hydrogel
• Small inconsistencies in the measuring of the contained fluids
• Small inconsistencies in the ratio of acidity or alkalinity in the environmental fluid

Works Cited bock, n. Hydrogels as Drug Delivery Systems: A Review of Current Characterization and Evaluation Techniques, https://pmc.ncbi.nlm.nih.gov/articles/PMC7762425/. Accessed 24 January 2026. “Diffusivity.” Hydrogel Design, https://hydrogeldesign.org/diffusivity/. Accessed 2 January 2026. Erikci, Saliha, and Joachim Spatz. “Kinetic and Mechanistic Release Studies on Hyaluronan Hydrogels for Their Potential Use as a pH-Responsive Drug Delivery Device.” MDPI, 12 November 2024, https://www.mdpi.com/2310-2861/10/11/731? Accessed 24 January 2026. Goforth\, Cynthia. “Fick's First Law of Diffusion | Equation & Example - Lesson.” Study.com\, https://study.com/learn/lesson/ficks-first-law-equation-examples.html. Accessed 2 January 2026. Patel, Megha. “pH stimuli-responsive hydrogels from non-cellulosic biopolymers for drug delivery.” Frontiers, 11 September 2023, https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2023.1270364/full? Accessed 24 January 2026. “pH in the Human Body.” News-Medical.Net, https://www.news-medical.net/health/pH-in-the-Human-Body.aspx. Accessed 2 January 2026. pH Sensitive Hydrogels in Drug Delivery: Brief History, Properties, Swelling, and Release Mechanism, Material Selection and Applications, https://pmc.ncbi.nlm.nih.gov/articles/PMC6432076/. Accessed 24 January 2026. Rizwan, Muhammad. “pH Sensitive Hydrogels in Drug Delivery: Brief History, Properties, Swelling, and Release Mechanism, Material Selection and Applications.” MDPI, https://www.mdpi.com/2073-4360/9/4/137? Accessed 24 January 2026. torchilin, v. “Hydrogels and Their Applications in Targeted Drug Delivery.” PubMed Central, 8 February 2019, https://pmc.ncbi.nlm.nih.gov/articles/PMC6384686/. Accessed 24 January 2026. “Understanding the Key Properties of Gelatin for Optimal Manufacturing Applications.” Funningpu, Funningpu, 12 October 2024, https://www.fnp-gelatin.com/news/understanding-the-key-properties-of-gelatin-for-optimal-manufacturing-applications.html#:~:text=The%20isoelectric%20point%20of%20gelatin,gelatin%20for%20particular%20applications%E2%80%8B. Accessed 6 January 2026. Varshosaz, J., and M. Falamarzian. “Drug diffusion mechanism through pH-sensitive hydrophobic/polyelectrolyte hydrogel membranes.” 2001, https://www.sciencedirect.com/science/article/abs/pii/S0939641101001266#:~:text=This%20hydrogel%20is%20quite%20hydrated,of%20the%20solutes%20%5B3%5D. Accessed 28 December 2025. Yanagida, Toshio, and Akihiko Ishijima. “Brownian Movement.” Science Direct, Science Direct, 2025,https://www.sciencedirect.com/topics/physics-and-astronomy/brownian-movement#:~:text=In%20subject%20area:%20Physics%20and,How%20useful%20is%20this%20definition? Accessed 2 January 2026.

I would like to thank my parents for supporting me while I was working on this project. I would also like to thank Mr. DeGelder, Ms. Shoults,Ms. Bly, and Ms. Martin for answering my questions regarding the Science fair and offering their support where it was needed.