Yan Liang Zhang

Piezoresistivity Characterization of Synthetic Silicon Nanowires Using a MEMS Device

This paper presents a microelectromechanical systems (MEMS) device for simultaneous electrical and mechanical characterization of individual nanowires. The device consists of an electrostatic actuator and two capacitive sensors, capable of acquiring all measurement data (force and displacement) electronically without relying on electron microscopy imaging. This capability avoids the effect of electron beam (e-beam) irradiation during nanomaterial testing. The bulk-microfabricated devices perform electrical characterization at different mechanical strain levels. To integrate individual nanowires to the MEMS device for testing, a nanomanipulation procedure is developed to transfer individual nanowires from their growth substrate to the device inside a scanning electron microscope. Silicon nanowires are characterized using the MEMS device for their piezoresistive as well as mechanical properties. It is also experimentally verified that e-beam irradiation can significantly alter the characterization results and must be avoided during testing.

A microfluidic device for simultaneous electrical and mechanical measurements on single cells

This paper presents a microfluidic device for simultaneous mechanical and electrical characterization of single cells. The device performs two types of cellular characterization (impedance spectroscopy and micropipette aspiration) on a single chip to enable cell electrical and mechanical characterization. To investigate the performance of the device design, electrical and mechanical properties of MC-3T3 osteoblast cells were measured. Based on electrical models, membrane capacitance of MC-3T3 cells was determined to be 3.39±1.23 and 2.99±0.82 pF at the aspiration pressure of 50 and 100 Pa, respectively. Cytoplasm resistance values were 110.1±37.7 kΩ (50 Pa) and 145.2±44.3 kΩ (100 Pa). Aspiration length of cells was found to be 0.813±0.351 μm at 50 Pa and 1.771±0.623 μm at 100 Pa. Quantified Youngs modulus values were 377±189 Pa at 50 Pa and 344±156 Pa at 100 Pa. Experimental results demonstrate the devices capability for characterizing both electrical and mechanical properties of single cells.

Automated nanomanipulation for nanodevice construction

Nanowire field-effect transistors (nano-FETs) are nanodevices capable of highly sensitive, label-free sensing of molecules. However, significant variations in sensitivity across devices can result from poor control over device parameters, such as nanowire diameter and the number of electrode-bridging nanowires. This paper presents a fabrication approach that uses wafer-scale nanowire contact printing for throughput and uses automated nanomanipulation for precision control of nanowire number and diameter. The process requires only one photolithography mask. Using nanowire contact printing and post-processing (i.e. nanomanipulation inside a scanning electron microscope), we are able to produce devices all with a single-nanowire and similar diameters at a speed of ~1 min/device with a success rate of 95% (n = 500). This technology represents a seamless integration of wafer-scale microfabrication and automated nanorobotic manipulation for producing nano-FET sensors with consistent response across devices.

Friction compensation with estimated velocity

The problem of friction compensation at very low velocity is investigated experimentally. Two published friction compensation strategies, based on two well-known friction models, are evaluated experimentally on a direct drive robot arm. One is an adaptive nonlinear dynamic friction compensation method using the LuGre friction model, and the other is a decomposition-based friction compensation method based on a friction model parameter linearization approach. In the experiments, a new velocity estimation method is implemented. The method significantly improves the effectiveness of friction compensation for all tested methods.

A compact closed-loop nanomanipulation system in scanning electron microscope

This paper presents a nanomanipulation system for operation inside scanning electron microscopes (SEM). The system is small in size, capable of being mounted onto and demounted from an SEM through the specimen exchange chamber without breaking the high vacuum of the SEM. This advance eliminates frequent opening of the high-vacuum chamber, thus, incurs less contamination to the SEM, avoids lengthy pumping, and significantly eases the exchange of endeffectors (e.g., nano probes and grippers). The system consists of two independent 3-DOF Cartesian nanomanipulators based on piezo motors and piezo actuators. High-resolution optical encoders are integrated into the nanomanipulators to provide position feedback for closed-loop control. A look-then-move control system and a contact detection algorithm are implemented for horizontal and vertical nanopositioning. The system design, system characterization details, and system performance are described.

Automated nanomanipulation for nano device construction

Nanowire field-effect transistors (nano-FETs) are nano devices capable of highly sensitive, label-free sensing of molecules. However, significant variations in sensitivity across devices can result from poor control over device parameters, such as nanowire diameter and the number of electrode-bridging nanowires. This paper presents a fabrication approach that uses wafer-scale nanowire contact printing for throughput and uses automated nanomanipulation for precision control of nanowire number and diameter. The process requires only one photolithography mask. Using nanowire contact printing and post processing (i.e., nanomanipulation inside scanning electron microscope), we are able to produce devices all with a single nanowire and similar diameters at a speed of ~1 min/device with a success rate of 95% (n=500). This technology represents a seamless integration of wafer-scale microfabrication and automated nanorobotic manipulation for producing nano-FET sensors with consistent response across devices.

Novel MEMS grippers capable of both grasping and active release of micro objects

Due to force scaling laws, adhesion forces at the micro scale make rapid, accurate release of micro objects a challenge in pick-place micromanipulation. This paper presents a new MEMS microgripper integrated with a plunging mechanism to impact the micro object for it to gain sufficient momentum to overcome adhesion forces. The performance was experimentally quantified through the manipulation of 7.5–10.9µm borosilicate glass spheres in an ambient environment under an optical microscope. Experimental results demonstrate that the microgripper achieves a 100% successful release rate (based on 200 trials) and a release accuracy of 0.70±0.46µm. Experiments with conductive and nonconductive substrates also confirmed that the release process is not substrate dependent.

Nanorobotic Manipulation of 1D Nanomaterials in Scanning Electron Microscopes

Nanorobotic manipulation inside a scanning electron microscope (SEM) has been used for maneuvering nanomaterials and nanostructures, charactering material properties, and assembling nanoscaled devices. Teleoperation with joysticks is most often used for controlling motions of nanomanipulators. Progress is being made toward automated nanomanipulation using SEM as a vision sensor. This chapter reviews systems, techniques, and applications of SEM nanomanipulation of 1D nanomaterials.

A micro device for impedance and mechanical characterization of biological cells

This paper presents a microfluidic device for simultaneous electromechanical characterization of single cells. The device performs two types of cellular characterization (impedance spectroscopy and micropipette aspiration) on a single chip to enable cell electrical and mechanical characterization. To investigate the performance of the device design, electrical and mechanical properties of MC-3T3 osteoblast cells were measured. Based on electrical models, membrane capacitance of MC-3T3 cells was determined to be 3.39±1.23 pF and 2.99±0.82 pF at the aspiration pressure of 50 Pa and 100 Pa, respectively. Cytoplasm resistance values were 110.1±37.7 kΩ (50 Pa) and 145.2±44.3 kΩ (100 Pa). Aspiration length of cells was found to be 0.813±0.351 µm at 50 Pa and 1.771±0.623 µm at 100 Pa. Quantified Youngs modulus values were 377±189 Pa at 50 Pa and 344±156 Pa at 100 Pa. Experimental results demonstrate the devices capability for characterizing both electrical and mechanical properties of single cells.

Effect of electron-beam irradiation on electrical characterization of nanowires in scanning electron microscope

The characterization of electrical properties of individual nanowires/nanotubes inside scanning electron microscopes has been demonstrated. However, the effect of electron-beam irradiation on the characterization results is not clearly known. Using a MEMS device we developed for the electromechanical characterization of nanowires, this study reveals that electron irradiation significantly alters the measured current-voltage characteristics of nanowire specimens. Single silicon nanowires are characterized using this MEMS device. The electron irradiation effect is quantified.