A month ago, Wu Yulu sold his "son" for 30,000 yuan (US$3,750).

Wu Laowu (the fifth son of the Wu family), is, well, a robot Wu made with his own hands 10 years earlier.

"I couldn't sleep well for several days after selling the child, but I had no other choice. I had to pay off my debts," said Wu, 44, a farmer from Mawu village in eastern Beijing.

Wu Yulu and his latest robot. [China Daily]

On his TV screen, he plays a video of Wu Laowu, serving tea and lighting cigarettes.

In the past 26 years, Wu Yulu has made 25 robots, and "all of them were like my sons."

Wu had a way with machinery and mechanics from childhood.

"Sometimes when people passed by, I would think about the mechanical functions of walking," Wu recalled.

Unfortunately, he could not pursue his passion through textbooks. He was one of five children in the family, and his parents could not support his education after he graduated from primary school in the mid-1970s.

But a lack of formal education did not deter Wu from copying what he called "marvellous human motions."

"At that time, I didn't even know the term 'robot'," Wu said. "But in my spare time from farming, I tried to collect everything that could be used in those movable things.

"I loved to play with robots. The cleverer they became, the deeper the emotional link I felt to them. Later, I began to call them my sons."

The wire, metal, screws and nails he used came from rubbish sites, or sometimes used parts from farm machinery.

In the late '70s, Wu got a job at a farm machinery factory, and the small income helped him turn used sewing machine parts and some steel wire into his first robot.

"Until now, I don't know the theory of physics, but I knew that electricity can drive motors and power can be transferred to the robot's hands and legs with levers and wires," Wu said.

After his first robot turned out to be "disabled," Wu continued to experiment. In 1982, the first movable robot, Wu Laoda (the first son of the Wu), was born.

Another video shows Wu Laoda as a coarse combination of steel wires and sticks without head and skin. He was destroyed in a fire seven years ago.

Although Wu compensated for his lack of scientific knowledge with his talent and devotion, there were accidents, the first of which happened around 1995.

"I got a rechargeable battery-like tube for a very low price from a recycling shop, thinking I could save money," Wu said.

But he did not understand the English warning on the tube, and "when I tested the tube, it exploded in my hands. I remember a big fireball suddenly burst out, and I lost my memory."

Luckily, neighbours rushed him to hospital. His memory returned, but the scars on his hands and arms and the pain he frequently feels in his wrists will last forever.

Another fire broke out in 1999 when Wu left a transformer unattended to repair a piece of farm machinery.

"Just as I was enjoying the praise for my skills in repairing, someone rushed in and said: 'Wu, your home is on fire,'" he recalled.

It was too late. No one was injured, but all six rooms with his belongings, including some robots, were destroyed.

"I was left with nothing," Wu said.

Neighbours, and even strangers, gave him money to rebuild his house, with no mention of repayment. Three months later, Wu was in a new home, costing 90,000 yuan (US$11,250).

Wu was determined to repay them but his pursuit of building robots did not leave much savings.

His son Wu Hongfeng said: "With his skills, my father could have become rich by making more profitable tools, but after the fire, the whole family was preoccupied with repaying our debt."

Wu Yulu eventually decided to sell some of the robots that had been stored elsewhere.

"I felt terrible, but had no choice," he said.

An institute affiliated to the Chinese Academy of Sciences bought one of the robots for "several thousand," Wu said, and a collector bought another.

Wu's perseverance finally began to pay off.

Feature stories on the "farmer inventor" began appearing in various media.

After one report on China Central Television (CCTV), its science channel hired Wu as a prop-maker, paying more than 3,000 yuan (US$375) a month.

Each week he goes to CCTV for orders and makes them at home.

Selling robot Wu Laowu helped speed the repayment of his loan. "The neighbours would not mention money, but I had to show them some consideration," he said.

Last month, Wu made the headlines again for a new invention, a robot able to pull a rickshaw one step every three or four seconds.

Sitting in the rickshaw, Wu said he has no plans to start a robot business.

"I can invent robots able to carry a sedan chair, and next I will make robots of the 12 animals in the Chinese zodiac.

"There are so many good things in life, and they become the basis for my robots."