Gardner's Kickstarter campaign for the Polar Pen had a goal of raising $14,000. As of noon Wednesday, it had raised more than $790,000.
Gardner, from Waterloo, isn't sure why his pen is so popular, but suspects it has to do with the YouTube video he made.
"It had 30 hits one day and by the next day it had over a million hits, so it went viral somehow. That day we did very good and since then we've been exploding," he told Craig Norris, host of CBC's The Morning Edition, on Wednesday.
"We were initially hoping to make between maybe 500-2,000 units, and we're at well over 20,000 units," said Gardner, who said details about how the requested pens will be manufactured are still being worked out.
But he says Health Canada has asked Gardner for more information about his pen, over concerns about the size of the magnets and the danger they could pose to small children, if swallowed. Earlier this year, Health Canada issued a recall for small, powerful magnet sets such as Buckyballs, which are banned in Canada.
If the health agency decides Gardner's pen is a hazard, he won't be able to manufacture or sell it in Canada.
CBC News called Health Canada on Wednesday afternoon for comment, but the call wasn't immediately returned.
How the pen works
The Polar Pen is made of round, hollow magnets created from the rare chemical element neodymium.
"Basically there's 12 or 13 individual magnets that all snap together into a cylindrical tube," said Gardner.
"And then you put on these different metal, steel components that snap on to the metal."
The Polar Pen comes with an ink cartridge, but can also be used as a stylus by adding another magnet and a rubber tip. In his YouTube videos, Gardner shows how the pen can be formed into a compass or used to make other toys, like spinners.
"The pen cartridge actually acts as a bit of an axle so you can make these interesting forms," he said.
Gardner says the magnets don't affect flash or solid-state hard drives, and the pen with the stylus tip is safe to use use on Apple, Samsung and BlackBerry tablet devices.
The Polar Pen sells for $35 to 40 on Kickstarter. The campaign ends at 11 p.m. ET Wednesday.
Considering manufacturing options
Gardner says Health Canada has asked for more information about the product, and has informed him there's a possibility his pen might fall under the magnetic toy category.
"I guess just from the sheer exposure we had, people are looking at you through different eyes," said Gardner.
In May, the health agency issued the Buckyballs recall after determining they were a "danger to human health and safety."
"The funny thing is, is you can buy these magnets in any local hardware store. There are actually three retailers in Waterloo that retail magnets very similar, if not even smaller," said Gardner.
If Health Canada cracks down on the Polar Pen, "That would be really unfortunate," said Gardner. "I guess we'd have to find, potentially, manufacturing outside the country. We're obviously not going to do anything illegal here."
For Canadians who supported the campaign on Kickstarter, Gardner said, he'll refund most of their money if he can't sell the pen in Canada.
"We have had to put in a stipulation that we cannot refund the eight per cent Kickstarter takes, just because it could put our company out of business before we've even started," he said.