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Detailed JELL-O® Chip Fabrication Protocol

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List of Materials Required for Jell-O® Chip Fabrication

  • Two 85g boxes of lemon-flavored Jell-O® jelly powder (Kraft Canada)
  • One pouch (7g) of unflavoured (the Original) Knox Gelatine (Associated Brands LP)
  • 2 beakers of 120mL of purified water for dissolving Jell-O® and Knox Gelatine
  • Six 6" foam plates, round (Safeway Limited Canada)One drinking straw, round (Safeway Limited Canada)
  • PAM® Original no-stick cooking spray (ConAgra Foods Canada Inc.)
  • Several 7" wooden coffee stirrers (Starbucks Coffee Company Canada)
  • Food-grade colour dye, green (McCormick Canada)
  • Single and double-sided tape (3M Canada)
  • Six 5" aluminum weighing pan (Cat No. 12175-001, VWR International)

Sources of Chemicals and Materials

Lemon-flavored Jell-O® Jelly Powder, unflavoured gelatin, round foam plates (6"), drinking straws, no-stick cooking spray, wooden coffee stirrers (7"), food-grade colour dyes, and single- and doublesided tape were obtained from local convenience stores. Aluminum weighing pans (5"), 10 mL syringes and Disposable Transfer Pipets were purchased from VWR International. ColorpHast Indicator Strips (pH 0-14) were acquired from EM-Reagents. Sodium Hydroxide (NaOH) and Hydrochloric Acid (HCl, 37% A.C.S. reagent) were obtained from Sigma. All solutions were prepared using ~18.2 MOhm-cm water treated with a water purification system (Barnstead EASYpure® II Ultrapure).

Jell-O® Chip Fabrication

Initially, the molds with desired features were made using foam plates, coffee stirrers and doublesided tape. To make the chips, two pouches of Jell-O® jelly powder were dissolved in 120 mL of purified water in a beaker. One pouch of Knox Gelatine powder was dissolved in the same amount of water in a second beaker. The beaker containing the Jell-O® solution was placed on a hot plate and heated to a boil. This beaker was removed from the heat and the gelatin solution was added to it. The mixture of Jell-O® and gelatin solution was again heated to a boil and removed from the heat. Prior to pouring the mixture of Jell-O® and gelatin solution into the mold, cooking spray was dabbed onto the inside rim of the foam plate to facilitate the peeling process after curing. The mixture solution was poured into six molds and they were transferred to a 4°C refrigerator for curing. Curing the chips overnight was usually sufficient; however, curing for at least two days in the refrigerator resulted in more robust Jell-O® chips. After curing, Jell-O® chips were carefully peeled off and placed on aluminum pans for experimental demonstrations. Lemon-flavored Jell-O® jelly powder was used because it produced chips with the best optical transparency. Inlet and outlet holes were punctured using a drinking straw. In all of the chips produced, the natural and reversible seal between the Jell-O® chip and the aluminum pan was adequate for the flow rates that were encountered. Lawson and Abbot, both high school students in Vancouver, BC, fabricated the chips and conducted the initial experiments presented here, demonstrating the accessibility of this technology to students at this educational level.

Module I: Pressure-driven flow

  • Materials Required:One Jell-O® microfluidic chip with a continuous channel depicting the letters "JELLO" (see Supporting Information regarding detailed chip fabrication protocol)
  • One 5" aluminum pan (Cat No. 12175-001, VWR International)
  • One disposable transfer pipet (Cat No. 16001-178, VWR International)
  • A small vial of water with a few drops of green food coloring dye (~30mL)

Mold Fabrication Guide:

The coffee stirrers were cut into rectangular shapes of various lengths. They were then taped onto the foam plate, forming the letters "JELLO", using double-sided tape. Singlesided tape was taped at junctions of coffee stirrers to ensure a smooth overall mold surface.

Additional Tips:

The Jell-O® chips should be stored in the 4°C refrigerator until immediately prior to peeling the chips and running the experiments. Thicker chips can be made by reducing the number of molds made (to three or four). However, increasing the thickness of the chips will most likely affect and lengthen the curing time. From experience, a ratio of 4 people per chip is adequate for these demonstrations.

Module II: Dimensionless parameters

Materials Required:

  • One Jell-O® microfluidic chip with a Y-shaped channelOne 5" aluminum pan (Cat No. 12175-001, VWR International)
  • Two disposable BD 10mL syringes (Product No. 309604, BD Canada)
  • A small vial of water (~30mL)
  • A small vial of water with a few drops of blue food coloring dye (~30mL)

Mold Fabrication Guide:

Two pieces of coffee stirrers were required for forming the Y-channel mold. A long rectangular-shaped coffee stirrer was first obtained (~3 inches long) by trimming the first coffee stirrer at both ends. One end of this coffee stick should be flat (outlet) and the other end should be dagger-shaped. The second coffee stirrer can be cut into two smaller rectangular-shaped sticks of the same length (~1 inch long). The longer coffee stirrer was taped near the middle of the foam plate using double-sided tape. The two smaller sticks were similarly taped at the dagger-shaped end of the longer stick, forming a mold with the letter "Y". Single-sided tape was taped at the junction of three coffee stirrers to ensure a smooth mold surface.

Additional Tips:

To prevent leaking from the inlets, the syringes should be perfectly perpendicular with the surface, and the head of the syringes should completely seal the inlets. Both clear and green water should be injected slowly but evenly into the channels, in order to create the laminar flow profile. The most common problem we encountered with the Y-Channel chip was with peeling the chip off of the mold, especially at the junction of the three coffee stirrers. Patience, care, and experience will help with the peeling process. If Y-Channel chips are too difficult to make, simple T-Channel chips can also produce the same results. Two rectangular-shaped coffee stirrers can be combined to make the letter "T" on a foam plate. Two inlet holes and one outlet hole should still be punctured as before. Laminar flow profile can still be seen with the T-Channel chips.

Module III: Fundamentals of pH Sensing & Parallelization

  • Materials Required:One Jell-O® microfluidic chip with two straight channels
  • One 5" aluminum pan (Cat No. 12175-001, VWR International)
  • Two disposable transfer pipets (Cat No. 16001-178, VWR International)
  • Two small pieces of acid-sensing pH paper (Cat No. 9590, EM Science)
  • Two small pieces of base-sensing pH paper (Cat No. 9590, EM Science)
  • A small vial of 1M hydrochloric acid (258148, Sigma-Aldrich) (or cooking vinegar)
  • A small vial of 1M sodium hydroxide (S8045, Sigma-Aldrich) (or dissolved antacid solution)

Mold Fabrication Guide:

Two pieces of coffee stirrers were required for forming the pH Sensor mold. Two long rectangular-shaped coffee stirrers of the same length were obtained (~2.5 inches long). These sticks were then taped onto the foam plate using double-sided tape, at ~1 inch apart.

Additional Tips:

Extreme caution should be taken when working with one-molar NaOH and HCl. Constant supervision is required, and this step is not suitable for younger students. Household solutions that are milder may be used instead of HCl and NaOH. Common acidic solutions include vinegar and lemon juice; common basic solutions include dissolved antacid solutions and soapy water.

 

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jello.flv1.52 MB
y-chip.flv1.22 MB