A group of ants can move objects many times larger and heavier than themselves. This ability inspired a team of researchers to develop small robots that can do the same thing. The team created 29 millimeter long robots that can get a firm grip on the ground. In tests， six of the robots have just worked together to tow a full-size car.

They didn't move the car quickly. To haul it 12.5 centimeters took about one minute.

When ants carry a large item， such as a piece of food， they need good traction. To get a better grip， each ant presses its feet down harder. This increases the area of contact between each foot and the surface. Such ants served as the inspiration for David Christensen and his team of mechanical engineers at Stanford University California.

Ants can cling to a smooth wall or surface using small pads on their feet. When an ant puts its foot down， a tiny droplet of sticky gel oozes between the pad and wall. This holds the ant in place. When walking， only tiny bits of the ant's feet stick to the ground. That makes it easy for the ant to move quickly. The mechanical engineers wanted to create miniscule robots capable of moving big， heavy objects. But robots can't ooze liquid the way ants do. Using sticky gel wasn't an option for the tiny bots. So the researchers turned their attention to gecko feet.

The bottom of a gecko's foot has layers of tissue covered with tiny hairs. When the critter puts weight on the foot， those structures spread out. This increases contact between the foot and the surface to which the gecko clings. That contact allows van der Waals forces to hold the foot onto the surface. Van der Waals forces are tiny electrical attractions between molecules. By increasing the surface area between its foot and a leaf， wall or other object， the gecko uses enough van der Waals force to stay in place. Such stickiness is called adhesion.

微型機(jī)器人

蟻群能搬運(yùn)體積和重量數(shù)倍于自身的物體。這種能力激發(fā)了某研究小組的靈感，他們開發(fā)了能像螞蟻一樣搬運(yùn)數(shù)倍于自身體積和重量的物體的微型機(jī)器人。研究小組創(chuàng)造了29毫米長的機(jī)器人，這種機(jī)器人能夠緊緊地附著在地面上。測試中，其中的6個機(jī)器人協(xié)同工作拖動了一輛實(shí)際大小的小轎車。

機(jī)器人沒有快速搬動小轎車，而是用了大約1分鐘時間把小轎車拖動了12.5厘米。

當(dāng)蟻群搬運(yùn)像一塊食物這樣的大物件時，需要有良好的附著摩擦力。為了更好地附著在地面，每一只螞蟻必須更加用力將腳向下壓，這樣就增加了每一只腳與物體表面的接觸面。美國加州斯坦福大學(xué)的戴維·克里斯滕森和他的機(jī)械工程師團(tuán)隊從蟻群身上獲得了靈感。

螞蟻用腳上小小的爪墊就能黏附在光滑的墻面或物體表面。當(dāng)螞蟻將腳壓下時，在爪墊和墻面之間會慢慢滲出一小滴黏性的凝膠，幫助螞蟻固定在合適的位置上。當(dāng)螞蟻?zhàn)呗窌r，僅有一小部分腳著地，這樣使螞蟻很容易快速走動。機(jī)械工程們想要創(chuàng)造能夠搬動又大又重的物體的微型機(jī)器人，但是機(jī)器人不能夠像螞蟻那樣滲出黏性液體，使用黏性凝膠不是解決微型機(jī)器人附著力問題的選擇，所以，研究者們把他們的注意力轉(zhuǎn)向了壁虎的腳。

壁虎的腳底有層層覆蓋著微小毛發(fā)的組織，當(dāng)壁虎向腳部施加重量時，這些組織結(jié)構(gòu)就會伸展開來，這樣能夠增大腳和它所附表面的接觸面積。這種接觸所產(chǎn)生的范德瓦爾斯力使壁虎的腳能夠牢牢地附著在物體表面。范德瓦爾斯力是分子間的極小的電性吸引力。通過增加腳和葉子、墻壁或者其他物體的接觸面，壁虎能夠用足夠的范德瓦爾斯力使得自己附著在物體表面。這種黏性被稱為黏附力。