Conductive inks make it easy to draw circuits on almost any surface, including paper. Popular Science used a carbon-based paint to animate this amorous robot, but other products use emulsified metals, such as silver, to carry a current. Whatever your artistic preference, skip the greeting card aisle this year and put an extra twinkle—quite literally—in your sweetheart’s eye.
Materials (per card):
∙ Printer paper
∙ White card stock
∙ Red card stock
∙ Two 3mm high-efficiency LEDs (for eyes)
∙ Conductive ink (10ml makes about six cards)
∙ Two 3V coin batteries (type CR2025 works well)
Scissors, pencil, wire cutters, black pen, clear tape
1: Print the stencil onto the printer paper and cut it out, leaving a 1⁄2-inch margin. Flip it over, and rub the backside with a thick layer of pencil.
2: Trace the stencil’s heart onto the red card stock and cut out the design. Also cut a thin 1-inch-by-1⁄2-inch strip and fold it into a Z-shaped paper spring.
3: Cut out an 8-inch-by-5 1⁄2-inch piece of white card stock. Fold it in half to create a 4 1⁄4-inch-by-5 1⁄2-inch card.
4: Center the stencil—pencil side down—on the front of the card. Trace the printed lines to transfer the design onto the card in pencil.
5: Splay the leads of each LED flat, and trim them with the wire cutters, leaving about a 1⁄2-inch protruding from the bulb.
6: Pen all solid lines, then squeeze conductive ink along the dotted lines (including the heart’s). Use only a dab where each battery goes.
7: Bridge the two eye gaps with the LEDs while the ink is still wet. Note the polarity: A flat spot on every LED bulb indicates which of the two leads is negative.
8: Stick each battery into place. Don’t allow conductive ink to ooze to the edge and short out the batteries.
9: Dry for at least an hour. Tape one end of the paper spring between the batteries and the other end below the line of conductive ink on the cutout heart.
10: Press down on the robot’s spring-loaded heart to complete its wire-free circuit and impress your geeky Valentine.
Time: About 90 minutes.
Cost: A few dollars.
Difficulty: 1/5 stars