Strain engineering allows the physical properties of materials and devices to be widely tailored, as paradigmatically demonstrated by strained transistors and semiconductor lasers employed in consumer electronics. For this reason, its potential impact on our society has been compared to that of chemical alloying. Although significant progress has been made in the last years on strained nanomaterials, strain fields (which are of tensorial nature, with six independent components) are still mostly used in a scalar and/or static fashion. Here we present a new class of strain actuators which allow the three components of the in-plane stress tensor in a nanomembrane to be independently and reversibly controlled. The actuators are based on monolithic piezoelectric substrates, which are micro-machined via femtosecond-laser processing. Their functionality is demonstrated by programming arbitrary stress states in a semiconductor layer, whose light emission is used as a local and sensitive strain gauge. The results shown in this work open a new route to investigate and make use of strain effects in materials and devices.
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