It takes just a peek at the online store Condomania to appreciate the variety of condoms out there.

Flavors like island punch, banana split and bubble gum. Vibrating condom rings with batteries that last up to 20 minutes. Glow-in-the-dark condoms promising “30 minutes of glowing fun.”

Under “Celebrity Condoms,” there is the “Obama Condoms Stimulus Package,” each condom embossed with an image of the president giving two thumbs up.

But even if that presidential seal of approval were real, it would not overcome a chronic and serious public health obstacle: Most men do not like condoms.

Now an influential player in global health, the Bill and Melinda Gates Foundation, is getting into the game. The foundation just finished collecting applications for what it calls a Grand Challenge: to develop “a next-generation condom that significantly preserves or enhances pleasure.”

The goal is to address two significant problems: unintended pregnancies and sexually transmitted diseases like AIDS. Condoms cheaply and effectively prevent both, but only 5 percent of men worldwide wear them and there are 2.5 million new HIV infections a year. To stem that tide, health experts say, the number of men regularly using condoms needs to double.

“Decreased sexual pleasure is typically the predominant reason for not using them,” said Stephen Ward, a program officer for the Gates Foundation. “Can we actually make them more desirable? That’s what we’re shooting for.”

More than 500 applications poured into the Gates contest, which will award winners $100,000 this fall and up to $1 million subsequently. In a first for a Gates challenge, Ward said, people sent samples.

“Boxes of condoms, condom accessories, condom cases that look like something else so women can be very discreet while carrying them,” he said. “We received a completely stocked carrying case with condoms, lubricant and breath mints.”

Contestants have been advised not to discuss their applications publicly, meaning that the creator of a YouTube video who pitched Gates a condom applied via slingshot is probably not a serious contender.

But condom experts — some of whom have studied the subject for years — have ideas of what might work and what decidedly won’t.

“I don’t think we’ve seen the condom that knocks the socks off for everybody,” said Ron Frezieres, vice present of research and evaluation at the California Family Health Council, a longtime tester of condoms for industry, government and nonprofit organizations.

“Guys would like it if they, first of all, don’t believe they’re wearing it,” Frezieres continued. “And second of all, it’s got to be a little better than what they’re used to. We still have to find that perfect bullet.”

Perfect may not be the enemy of the good in this case, but it is awfully hard to pin down.

“When I saw that Gates announcement,” said Jeff Spieler, a senior technical adviser on population and reproductive health at the U.S. Agency for International Development, “I wrote and said, ‘It’s great that you’re doing this, but I’ve been there before, and I hope you’re going to surface something that I couldn’t surface.’ ”

Constantly in development

Several manufacturers have worked on more appealing condoms. Some models, like Pleasure Plus and Twisted Pleasure, designed by an Indian surgeon, Alla Venkata Krishna Reddy, whom Spieler called the “Leonardo da Vinci of condoms,” addressed complaints of tightness and friction. They are roomy, ballooning, “sort of like the swirl of a Dairy Queen ice cream,” Spieler said. The movement of extra material is intended to be stimulating.

Frezieres and his colleague Terri L. Walsh conducted studies involving condoms with lubricants that create a heating sensation. “Some people said, ‘This is burning me,’ ” he said, but others reported a mild, pleasant feeling or even more intense orgasms. On the other hand, as Walsh pointed out, a stimulating condom could make matters worse for men with premature ejaculation, so for them, the question is, “How much more exciting do you want to make a condom?”

Another testing quandary, Spieler said, is that “you can’t compare one sex act to another sex act. You can come into a sex act having just argued and having makeup sex. You could have three days of bad sex, so you don’t rate the condom you’re testing very well.”

That has not stopped innovation in the condom industry. There are vibrating condom rings like the Durex Play – Ring of Bliss, said Bidia Deperthes, a senior HIV technical adviser for the U.N. Population Fund. (Spieler calls her “the condom czarina.”) Some men invariably gripe about the battery life: “Bidia, 20 minutes, it’s not that long.” Her response: “Guys, give me a break. Fifteen minutes is already flattering you.”

Deperthes, whose office features a wall of condoms, has versions packaged like lollipops, miniature chocolate milk cartons and cellophane-wrapped taffy.

And what’s that pinned to her silk blouse? A brooch of batik fabric. But on the flip side of the pin is, yes, a condom. Talk about wearable art.

One unsuccessful innovation was the Hat condom, resembling a little shower cap, designed, said Frezieres, “to fit just over the tip,” to “provide maximum sensation.” Alas, “in clinical testing, couples experienced difficulty keeping the Hat condom from popping off,” he said.

‘Great concept’ falters

Another idea was the spray-on condom, applying liquid latex to create a condom shaped for the man using it. “Great concept,” Frezieres said. But it did not have a tip to collect fluid, and “we were like, how do you get it off afterward?”

One promising design, already available in some parts of the world, is the Pronto 4:Secs condom, its box decorated with racy Dick Tracy-esque cartoons. 4:Secs, its name both a pun and the time it is supposed to take to put on, is a condom in a plastic applicator resembling a life preserver.

“This is really cool,” said Deperthes, demonstrating how the applicator splits apart to allow the condom to be put on right-side up.

And perhaps the most innovative new American-made product is the Origami condom, still in clinical trials. Its inventor, Danny Resnic, said he was motivated by his own experience when “a latex condom broke and I wound up with an HIV diagnosis.”

Years of experimenting led him to devise a condom with accordionlike pleats, loose to allow movement inside. Made of silicone, which is meant to feel more like skin, it “goes on in less than a second,” he said, and “there’s no wrong way to put it on.”

The Gates Foundation contest also welcomed designs for female condoms, but female condoms have historically been less popular.