Food Grows By Itself!
Did you know that there are hundreds of invasive wild edibles which are often illegal to grow, because they crowd out other (often useless) plants? One you might be familiar with is Kudzu, which grows all over the southern USA. It’s both edible and medicinal. Here’s some Gemini Deep Research reports on building your own no-work (plant and forget), invasive food forest in various climate zones.
Here’s a video someone sent me about one of the most useful complete foods you may have never heard of: Duckweed. It’s even more complete than spirulina, and it grows easier. What the video should have also mentioned is: There’s only one duckweed, Wolffia globosa, which has both high protein but also low enough oxalate levels to be consumed in quantity. That one grows in tropical climates. And the issue that remains with Wolffia is it accumulates too much manganese, so you wouldn’t be able to use it as a primary food source unless you use another water plant like Pistia stratiotes or Salvinia natans, which is even better at Mn accumulation, and then just pluck those out and toss them away as they surface.
Water In The Desert!
Unfortunately…
About 2 billion people in the world today face water scarcity. While rainwater harvesting (and purification) would work for half of those people, if they could afford the initial investment in a rain harvesting system, the rest live in arid or semi-arid regions where it would not work.
Fortunately…
Now it is possible for those 1 billion people to harvest water from the air, using Ultrasonic Atmospheric Water Generators (AWG).
Below is the updated guide:
DIY Project: High-Efficiency Ultrasonic Water Harvester
Based on MIT Device Research Lab Prototypes (2024-2025)
1. Project Overview
This guide outlines how to build a small-scale atmospheric water harvester that uses ultrasonic vibration instead of heat to extract water from air. This method is significantly more energy-efficient than boiling or heating, allowing it to run on a small solar panel.
How it works:
Capture: A “super-sponge” (Hydrogel + Salt) sits in the air and sucks up moisture, even in dry deserts.
Release: Instead of heating the sponge, we blast it with high-frequency sound (113,000 vibrations per second).
Harvest: The water shakes loose as droplets and falls into a cup.
Warning: This project involves chemicals (Lithium Chloride) that are safe when handled correctly but can be an irritant. The resulting water must be tested before drinking.
2. Bill of Materials (BOM) & Costs
Estimated prices are based on US online retailers (Amazon, AliExpress, eBay).
A. The “Sponge” (Sorbent Materials)
The secret sauce is a mixture of Polyacrylamide (the structure), Lithium Chloride (the magnet for water), and Glycerol (the stabilizer).
ComponentDescriptionWhere to BuyEst. CostPolyacrylamide (PAM)
Option A (Easy): “Soil Moisture Crystals” or “Hydrogel Beads” (Look for Polyacrylamide specifically, not just generic water beads which are often sodium polyacrylate).
Option B (Pro): Lab-grade Polyacrylamide powder.
Garden stores, eBay, Lab supply$10 - $15Lithium Chloride (LiCl)Hygroscopic salt. Do not use Lithium batteries. You need the chemical reagent powder.eBay, Science supply (e.g., Flinn Scientific, Carolina Biological)$30 - $40 (100g)Glycerol (Glycerin)Vegetable Glycerin (liquid). Prevents the salt from leaking out of the gel.Drugstore (Skin care section), Amazon$5 - $8Deionized WaterFor mixing.Grocery store (Distilled water)$1
B. The “Shaker” (Electronics)
We need a device that vibrates at exactly 113 kHz (108-113 kHz range).
ComponentDescriptionWhere to BuyEst. CostUltrasonic Mesh Atomizer ModuleCrucial Part. Look for “USB Humidifier Module 113kHz” or “Mesh Nebulizer Replacement”. Must include the driver board (PCB).AliExpress, Amazon, eBay$5 - $8 eachSolar Panel5V or 6V, 5 Watts. USB output preferred for simplicity.Amazon, Electronics hobby shops$10 - $15Battery (Optional)USB Power Bank (small) to run it at night or buffer solar power.Any electronics store$10Microcontroller (Optional)Arduino Nano or ESP32 (only needed if you want to automate cycles).Amazon, Adafruit$5 - $8
C. Hardware & Filtration
ComponentDescriptionEst. CostEnclosureSmall plastic food container or 3D printed housing.RecycleFan25mm or 30mm 5V Fan (tiny cooling fan).Electronics hobby shopTDS MeterMandatory Safety Tool. Measures Total Dissolved Solids (salt levels).AmazonActivated Carbon FilterBrita filter or generic inline carbon filter (to polish water taste).Grocery store
Total Estimated Build Cost: $90 - $120
(Cost drops significantly if building multiple units as chemicals are sold in bulk).
3. Step-by-Step Build Guide
Step 1: Prepare the Hydrogel Sorbent
This is the most critical step. We are hacking the MIT recipe for safety by soaking pre-made beads instead of synthesizing dangerous monomers.
Safety Gear: Wear nitrile gloves, safety goggles, and a dust mask. Lithium Chloride dust is an irritant.
Mix the Solution:
In a glass jar, dissolve 20 grams of Lithium Chloride (LiCl) into 20 ml of distilled water. Stir until clear. It may get warm (exothermic).
Add 20 ml of Glycerol to the mixture. Stir well. (The Glycerol is the “MIT Hack” to keep the salt trapped inside the gel).
Soak the Beads:
Take your dry Polyacrylamide crystals/beads.
Soak them in the LiCl/Glycerol solution.
Wait: Let them soak for 24-48 hours. They will swell and become rubbery, transparent disks/blobs.
Note: If they become too mushy, your salt concentration is too high. If they barely swell, add a little more water.
Drying (Activation):
Remove the swollen gels. Place them on a non-stick mesh or parchment paper.
Let them air dry in a warm spot or use a food dehydrator (low heat, ~50°C) until they shrink back down. They are now “charged” and ready to grab water.
Step 2: Hack the Atomizer
Most USB humidifier modules have an “Auto-Shutoff” timer (usually 4 hours). You want it to run on command.
Inspect the Board: Look at the small circuit board that came with your atomizer.
Bypass the Button (If using Arduino): Solder two wires to the legs of the push-button. Connecting these wires simulates a button press.
The Mesh Orientation: The metal disk has a “wet” side and a “dry” side.
Standard use: Water is under the mesh, sprays up.
Our use: The Hydrogel sits on top of the mesh. The vibration pulls water through the mesh downwards.
Action: Mount the mesh disk horizontally, so the side with the wire leads is facing UP.
Step 3: Assembly
The Chamber: Cut a hole in the lid of your collection container (the “Clean Water Tank”). Glue the Ultrasonic Mesh Disk over this hole.
Placement: Place your “Charged” Hydrogel disk directly on top of the Mesh Disk.
Tip: Use a small piece of plastic window screen or a rubber O-ring to gently hold the gel against the metal mesh. Good contact is essential for the ultrasound to work.
Airflow: Mount the small 5V fan on the side of the container (above the mesh line) to blow ambient air over the hydrogel.
Wiring: Connect the USB humidifier board to the Solar Panel (or Battery).
4. Operation Cycle
You can run this manually or automate it with an Arduino.
Phase 1: Capture (Night/Morning)
Time: 60-120 minutes (depending on humidity).
Action: Turn ON the Fan. Turn OFF the Ultrasonic Mesh.
What happens: The LiCl-infused gel sucks moisture from the air. It will swell and look wet.
Phase 2: Harvest (Day/Sun)
Time: 10-20 minutes.
Action: Turn OFF the Fan. Turn ON the Ultrasonic Mesh.
What happens: You will see a fine mist or droplets shooting through the bottom of the mesh into your cup. The gel will shrink as it loses water.
Phase 3: Reset
Repeat Phase 1.
5. Safety & Water Quality
Is the water safe to drink?
Not immediately.
The Risk: If the gel breaks down, Lithium Chloride (LiCl) can enter the water. LiCl is used in medicine but toxic in high doses.
The Test: Use your TDS (Total Dissolved Solids) Meter.
Pure distilled water is ~0-10 ppm.
Tap water is ~150-300 ppm.
Fail: If your harvested water reads >500 ppm, the salt is leaking. DO NOT DRINK. Rinse the gel and try again, or discard the gel.
The Fix:
Filter: Always run the harvested water through an activated carbon filter.
Taste Test: If it tastes salty, do not drink it.
6. Financial Breakdown: Cost per Liter
Is this cheaper than buying water? No. Is it cheaper than other atmospheric generators? Yes.
Assumptions:
Yield: A single 20mm mesh disk + 5g of gel can harvest approx. 10-20ml per cycle.
Cycles: 10 cycles per day = ~150ml/day.
Lifespan: The mesh nebulizer heads fail (clog/corrode) after ~1000 hours of operation (approx. 6-12 months).
Replacement Cost: $5 per mesh.
Cost Analysis (1 Year Operation):
Initial Build: $100
Replacement Meshes (2x): $10
Total 1st Year Cost: $110
Total Water Yield (150ml x 365 days): 54.75 Liters
Final Cost:
$2.00 per Liter (Year 1)
$0.20 per Liter (Year 2+ recurring costs only)
Conclusion:
This is currently a survival/science tool, not a municipal water replacement. However, compared to commercial Atmospheric Water Generators (which cost $1,000+ and use massive amounts of electricity), this DIY ultrasonic version is highly cost-effective for off-grid, emergency water generation.