## 1 Introduction  
Micro-electro-mechanical systems (MEMS), which are devices with electrical circuits, mechanical components, and electro-mechanical transducers, are now widely employed in various electrical systems, including those in automobile, portable, amusement, environmental, or infrastructure monitoring systems. The mechanical components in the conventional MEMS devices are only micrometers in scale and are based on well-developed semiconductor microfabrication technologies. Recently, for further miniaturization, higher performance, and more functionality, the integration of nanoscale components into MEMS has been widely investigated. These are referred to as nano-electro-mechanical systems (NEMS). The nano-carbons (graphene [1, 2], carbon nanotubes [3, 4], and fullerene [5]), biomolecules (proteins [6], lipids [7, 8], and nucleic acids [9, 10]), and metal nanoparticles [11, 12] are examples of nanoscale components that have been integrated into MEMS or microfluidic devices. They provide a new functionality, better sensitivity, and higher reliability. However, there continues to be problems with the mechanical and electrical interfaces in their integration with the microscale structures in MEMS devices.  
Silicon nanowire (SiNW) is also a candidate as a nanoscale component for mechanical or chemical sensing [13, 14, 15, 16, 17, 18, 19]. The piezoresistive strain gauge performs better when the dimensions are reduced [16, 17]. The higher surface-to-volume ratio provides a higher sensitivity to chemical and biological sensing, which works as a molecular-sensitive field effect transistor [18; 19]. One of the merits of using silicon is its well-developed fabrication technology. We can easily fabricate a nanowire on the substrate using nanoscale lithography and etching technology. However, creating a freestanding nanowire on a device is still a challenge. The pick-and-place technique was employed for the characterization of free-standing SiNWs fabricated using focused-ion-beam (FIB) processing [20; 21], however it is not compatible with large-scale fabrication. Local chemical vapor deposition (CVD) growth has been used, but it requires an additional structure for heating and may not be compatible with the device structures [18; 22]. Multi-step deposition and etching with wafer bonding has also been developed. The integration of MEMS and SiNW, using batch fabrication, has been achieved, however the fabrication process is costly [19]. An integration process that uses a simple silicon-on-insulator (SOI) wafer and standard process machines (deep reactive ion etching [DRIE]) is needed for low-cost fabrication to be realized.  
In this research, we have proposed a fabrication process for a free standing SiNW on a SOI wafer, in which a SiNW of a few hundred micrometers in diameter is integrated into a device layer of 5 micrometers thickness. In the same device layer, the electrostatic transducers, which are responsible for force actuation and displacement sensing, and for the mechanical components such as the mass and springs, are integrated. The advantages of this process are as follows:  
1. No interface between a MEMS device structure and a SiNW;
2. Perfect alignment; and
3. Free from a complicated and time-consuming assembly process.  
For a technical demonstration and material properties characterization, a MEMS tensile testing device for a SiNW of 100 nm thickness was fabricated and the tensile strength was measured in this research.