To solve a big environmental problem, chemists have been thinking small. Really small: a new mini robot with the purpose of helping clean up tiny plastic that pollutes water across the world.

The new microrobots, each of which is no bigger than the tip of a pencil, are magnetic(有磁性的)and shaped like four-pointed stars. When the sunlight shines on them, they can swim in a direction; when the sunlight disappears, they stop moving. Finding a piece of plastic, they hold onto it, produce chemical reactions and start to break it down.

The project is led by chemist Martin Pumera, a researcher who also studies ways to build microrobots at the Czech University of Chemistry and Technology in Prague. About ten years ago, he noticed the microplastic was everywhere, from the bottom of the ocean to the ice on the top of mountains. It even turned up in drinking water, both bottled and tap water. Just think about how much plastic you meet every day. It doesn’t easily degrade ( 降 解 ) which is a big problem. Therefore, Pumera chose to focus on the problem of water pollution caused by microplastic.

The researchers tested the microrobots on four types of plastic in the lab. After a week, all four began degrading, losing around 3 percent of their weight, which showed the microrobots were breaking the plastic down. The robots also turned the plastic’s smooth surface into the rough one. Finally, the scientists showed that magnets could attract the microrobots at the end of the test - along with the plastic waste.

In fact, Pumera says they still have a long way to go. These microrobots are unlikely to succeed in degrading all types of plastic. They’ll also need a lot of testing to show that they’re safe in open waterways, such as at sea. But he thinks that these challenges can be overcome. Someday, the microrobots will play a big role in a worldwide cleanup effort.

Steve Jobs was one of the fathers of the personal computing time and the founder of Apple. He was also one of the giants of the information age. Here are some of his greatest contributions.

Apple II Jobs and Steve Wozniak founded Apple Computers Inc. in 1976. A year later, the Apple II was invented. This production was the world’s first personal computer.	The iMac Under Job’s leadership Apple introduced the all-in-one iMac computer in 1998. The iMac became the first machine, which offered only a CD-ROM slot (狭孔).
The iPad By 2010, Steve Jobs was confident the world was ready to have a tablet computer that would be great for watching movies and playing games. The iPad is a great success.	iPhone 4s iPhone 4s came out on October 4, 2011, in America. It looks like iPhone 4. It has a large and wider screen and a better camera.

There’s a new frontier in 3D printing that’s beginning to come into focus: food. Recent development has made possible machines that print, cook, and serve foods on a mass scale. And the industry isn’t stopping there.

Food production

With a 3D printer, a cook can print complicated chocolate sculptures and beautiful pieces for decoration on a wedding cake. Not everybody can do that — it takes years of experience, but a printer makes it easy. A restaurant in Spain uses a Foodini to “re-create forms and pieces” of food that are “exactly the same,” freeing cooks to complete other tasks. In another restaurant, all of the dishes and desserts it serves are 3D-printed,rather than farm to table.

Sustainability(可持续性）

The global population is expected to grow to 9.6 billion by 2050, and some analysts estimate that food production will need to be raised by 50 percent to maintain current levels. Sustainability is becoming a necessity. 3D food printing could probably contribute to the solution. Some experts believe printers could use hydrocolloids (水解胶体) from plentiful renewables like algae(藻类) and grass to replace the familiar ingredients(烹饪原料). 3D printing can reduce fuel use and emissions. Grocery stores of the future might stock "food" that lasts years on end, freeing up shelf space and reducing transportation and storage requirements.

Nutrition

Future 3D food printers could make processed food healthier. Hod Lipson, a professor at Columbia University, said, “Food printing could allow consumers to print food with customized nutritional content, like vitamins. So instead of eating a piece of yesterday’s bread from the supermarket, you’d eat something baked just for you on demand.”

Challenges

Despite recent advancements in 3D food printing, the industry has many challenges to overcome. Currently, most ingredients must be changed to a paste(糊状物) before a printer can use them, and the printing process is quite time-consuming, because ingredients interact with each other in very complex ways. On top of that, most of the 3D food printers now are restricted to dry ingredients, because meat and milk products may easily go bad. Some experts are skeptical about 3D food printers, believing they are better suited for fast food restaurants than homes and high-end restaurants.