In the eight years since Zhang Shuxiang first left her village in the poor interior of central China, she worked in 20 factories before coming to the assembly line of a Foxconn plant making products for tech firms including Apple. She wants it to be her last.

The 26-year-old has worked in factories making products as varied as coffee makers, jewellery, Apple's LED screens and now computer motherboards. Each time, she quit, blaming low wages and unreasonable supervisors and joined yet another factory.

"Factory work is too tiring," she said when asked about life after Foxconn, which she plans to leave by June.

"Since last year, I've kept on telling myself I would never want to enter a factory ever again, but I'm still doing it in spite of myself."

She embodies the shifting expectations and opportunities of tens of millions of young Chinese workers from the countryside who have turned their country into a workshop of the world.

Their changing attitudes pose a deep challenge for thousands of manufacturers, such as Foxconn and its big customer Apple, which have relied on what they once thought was a virtually endless stream of inexpensive, compliant workers.

Foxconn chairman Terry Gou has pledged to keep on increasing worker salaries and cutting the hours of work, after it came under fire for poor working conditions for employees making Apple iPhones and iPads.

Zhang now works on an assembly line for motherboards, in a factory inside a mammoth industrial complex on the outskirts of Zhengzhou, which Apple Chief Executive Officer Tim Cook visited in late March during a trip to China.

Before finally deciding whether to quit, Zhang said she will wait to see what changes come from the agreement signed by Foxconn and Apple to improve working conditions.

Meeting the aspirations of Zhang and other migrant workers who power China's economy - officially estimated at 159 million - is crucial for the government.

Younger, better educated and more tech-savvy, many migrant workers grew up as the sole children in their families and are less accepting than their parents were of tough working conditions.

They are also becoming more aware of their rights and of the widening growing range of available jobs, including services, that has come with rapid economic growth and which offer a way out of the relentless tedium of factory work.

"They are willing to take collective action, strikes, work stoppages, protests when they feel their rights have been violated or what they are owed has not been given to them," said Geoffrey Crothall, a spokesman for Hong Kong-based workers' rights group China Labour Bulletin.

"Workers know that if they stand their ground and ask for better pay and conditions, employers...have to agree to some of their demands."

Duncan Innes-Ker, senior China analyst for the Economist Intelligence Unit, said there is a 'perfect storm of factors' coming together to support workers as they push for higher wages: sustained economic growth, government policy support for a higher minimum wage and demographics.

The number of young Chinese workers aged 15-24 years of age will likely fall by a third in the next 12 years, giving more bargaining power to this younger blue-collar generation, Beijing-based consultancy Dragonomics has projected.

The average monthly wage of China's migrant workers in 2011 rose 21.2 per cent from 2010 to 2,049 yuan, with wages higher in the more developed coastal areas like Guangdong.

Even so, despite the recent increases, such wages are still many times lower than in Western developed economies.

'I DON'T DO OVERTIME'
On a recent afternoon outside a labour market in Zhengzhou, the provincial capital of Henan, a scattering of people were scrutinising recruitment placards on a fence.

Companies were looking for store managers, retail assistants and accountants. Some were offering salaries that range from 1,200 to 6,000 yuan.

Xie Wen, 22, an unemployed former nurse, looked horrified when asked whether she was considering a job at a factory.

"It sounds good, but it's all menial work. If you want to earn a lot, you have to work a lot of overtime," she said, adding that she does not want her next job 'to be too tough. I don't want any night shifts and I don't do overtime'.

Her friend, Jin Jin, 27, who has been looking for work since she quit her job at a pharmacy a month ago, said she resigned because it was 'meaningless' work.

Since 2004, she has held four to five jobs and is now seeking one in sales that pays about 2,000 yuan, with about 4-6 days off a month, subsidised meals and overtime fees.

Clad in a black blazer, jeans and pink sequined shoes, Dou Jing, 20, said she worked in the quality control department in an electronics factory for a year after high school.

"It was very tiring. I had to work night shifts that lasted 12 hours," Dou said. She later found a job as a receptionist for a small company, greeting guests and pouring tea for them.

"I didn't feel I could learn anything," she said, adding she wanted to learn some skills in her next job and open a shop.

Walking through the crowd, a man surnamed Yang was trying to recruit telemarketers. He was distributing flyers that offered w a ges of 3,000 to 5,000 yuan a month, but not many people expressed interest.

"Workers are more choosy, they want a high salary, a job that's close to home and work that has very little responsibility," he said. "I think that's unrealistic."

Although the younger, more finicky cohort of migrant workers could pose a challenge for China's exporters, Innes-Ker said "we're still a long way away from the idea that foreign companies are moving out of China because it's too expensive."

"It's very difficult to find somewhere with the similar strengths of China," he said. "When it comes down to it, China has massive clusters that allow a very high degree of specialisation to occur, and that helps to push down costs quite dramatically."

'EAT BITTERNESS'
Zhang's elder brother, Zhang Junfeng, 30, who also works at Foxconn, said turnover is particularly rampant among younger factory workers, particularly those born in the 1990s.

"They'll resign the minute they get angry," Junfeng said. "Very few of them can eat bitterness."

Eating bitterness is an expression used by Chinese who have endured decades of natural and man-made hardships throughout China's tumultuous history - a term that also applies to Zhang's parents, who are both 61 and were farmers their whole lives.

On a recent afternoon, the pair sat in the courtyard of their home in Yezhang village, an hour's drive from Zhengzhou along several unpaved roads that cut through fields of wheat.

They were picking through freshly harvested spinach from their fields to sell in Zhengzhou.

Zhang laughed when asked how her life is different from her parents, whose faces are brown and wrinkled from the sun. "At that time how can there be factories? That time, there were communes," she said.

The round-faced Zhang, clad in a red tunic and black sweatpants, knows a thing or two about eating bitterness.

She was 18 when her mother paid a middleman 600 yuan to find her a factory job in Dongguan, a gritty city in Guangdong. When she arrived after a two-day rickety bus ride in 2004, she called home and cried to her mother after only a few days.

In a Foxconn factory in Longhua in a suburb of Shenzhen, Zhang said she was hospitalised for two weeks in late 2011, blaming her supervisor for setting unreasonable quotas. She finally protested with her feet, quitting after about three months.

In one day, Zhang is required to paste 5,000 round dots by hand on a component for motherboards.

Yet even with the tedious work, Zhang says conditions at the Zhengzhou factory are better than at the previous Foxconn factories where she's worked. Her workday is about eight hours and she is given eight days off a month.

Foxconn pays her a base salary of 1,550 yuan a month, an increase from 1,320 yuan the year before, and extra for overtime duty.

She lives four to a room in her dormitory, which she pays 150 yuan a month to rent and is spartan with just two metal bunk beds and a desk.

Back at the Foxconn factory in Shenzhen where Zhang worked in 2010, w orkers on the assembly line were banned from talking to one another and taking toilet breaks that exceed 10 minutes, according to Zhang.

"At that time, that made me think of the phrase: 'We're humans, we're not machines'," she said.