# A flexible printed circuit boardPCB#* Originally considered: A flexible board can be folded over to connect to both sides of the cell, and to create two rows of opposing contacts which can be pressed together by the user to form a connection (i.e., pushbuttons)#* Initial idea is to use a board about 55mm x 75mm (Now under consideration: Traditional PCB roughly business-card-sized) which will fold in half lengthwise 20x70 mm with a 5mm spacing between the top and bottom layers, yielding a device about 25x25x75mm (1x1x3"), containing the clips for cell, 3 or 4 user pushbuttonsESP module, and the ESP12F module#* A small piece of craft foam will likely need to low-profile tact buttons. Would be inserted into the middle of the device nice to provide stiffness, to separate the two layers, and to act as a spring to keep the user pushbuttons open when they are not depressed#* These circuits could be inkjet printed at the college, or a traditional copper flex circuit production run could be ordered#* The outside include unpopulated ("back"?) of the flex circuit could be printed with the pushbutton labels header for reprogramming after FSOSS, maybe some other unpopulated pads for LEDs and other information, or these could be added in the form of things that would make this a sticker.# A connection scheme to attach the cell fun and ESP12F to the flex useful hacker circuit#* Z-axis electrically conductive adhesive transfer tape (3M type 9703) is one option, though after the ESP12F circuit pads may be too small to permit reliable operation and sufficient current flow (approxevent. 1.5mm2, where the 3M documentation recommends 3.5mm2)#* Alternatives to z-axis tape include wire glue or conductive epoxy, but these limit options for reusing/recycling the device

The total target cost of the device will be in the is <C$3-5 range in the quantities needed for FSOSS (approximately 200-250 ~300 units). Total project cost may be slightly higher depending on what additional devices are required, e.g., development kits, inkjet circuit printer, battery chargers.