We present a microrobotic platform that combines MEMS-based capacitive force sensing technology, a dual-stage positioning system and a real-time control and acquisition architecture with computer vision automation to manipulate and mechanically characterize growing plant cells. The topography accuracy of the system, using a silicon wafer sample is measured to be 28 nm(1σ, 200Hz). With an SI-traceable stiffness reference we estimate the accuracy of the RT-CFM to be 3.49%. The target locations are selected from an interactive image of the workspace, and the sensing tip is positioned at each location using visual servoing techniques. Topography and stiffness maps were successfully obtained on growing pollen tubes. With the proposed system, cells can be mechanically stimulated at high speeds and with high precision while the intracellular components are visualized using confocal imaging. The system offers a versatile solution for dexterous and high-throughput characterization of biological specimen.

As the field of biology becomes a more quantitative and predictive natural science, an increasing need for investigation and quantification of the mechanics of growth at individual cellular levels arises. This paper describes a microrobotic force-feedback based system and its application to the mechanical characterization of living, growing plant cells. The Cellular Force Microscope (CFM) is capable of performing the automated mechanical characterization of living plant cells in situ as these cells proliferate and grow. The microrobotic measurement system employs a single-axis capacitive MEMS microforce sensor capable of resolving forces down to 20 nN (1¿, at 10Hz). A multi-axis positioning system with 5 nm resolution position feedback is integrated into a complete system with a high-resolution optical microscope and a custom user interface for guiding an automated force-based measurement process. The CFM has been applied to characterize the mechanical properties of 20¿m wide Lilium pollen tubes while they grow at a rate of about 10 ¿m/min in growth medium. For the mechanical characterization of pollen tubes, loads up to 400 nN are applied that cause indentations up to 300 nm. The force-deformation data acquired show an increase in the observed stiffness from the tip to the apex demonstrating that CFM is a promising tool for better understanding the changing mechanics of living plant cell growth.

This paper presents the design, fabrication and characterization of the first microfabricated three-axis tunable force sensor with sub-micronewton measurement uncertainty. The sensing range can be electrically tuned from +/-20 μN to +/-200 μN while taking measurements, ensuring optimal sensor characteristics for a large variety of applications. Since the sensor has been pre-calibrated for the entire tuning range the exact sensor gain and its uncertainty is known. Real-time, three degree of freedom force feedback makes this sensor a valuable tool for micromanipulation.

This work describes the design of a capacitive multi-axis force-torque sensor for the monitoring of forces in the sub-milli-Newton and sub-micro-Newtonmeter range. This force range makes it a valuable tool for microrobotic applications. The sensor is experimentally investigated and calibrated. This is the first microfabricated 6-axis force-torque sensor that has been successfully developed.

Self-assembly is a process in which individual components form an organized structure as a consequence of local interactions. When using magnetics to create interaction forces, the magnetic flux distribution of a self-assembling system changes as its assembly state varies. Since Hall effect sensors are a convenient and effective means to detect changes in the magnetic field, we explore their applicability to monitoring the morphology of such magnetically self-assembling systems. We find that optimal positions for the sensor can be found where the flux changes maximally. Our analysis is applied to two different systems by deriving the flux changes for all possible states, and theoretical flux changes are verified with experiments. In addition, we show that a small number of sensors is sufficient for robust state determination. In addition to state detection, experiments show the potential for angle measurement for compliant cylindrical magnet joints using a single Hall sensor.

Retinal vein occlusion is an obstruction of blood flow due to clot formation in the retinal vasculature, and is among the most common causes of vision loss. Currently, the most promising therapy involves injection of t-PA directly into small and delicate retinal vessels. This procedure requires surgical skills at the limits of human performance. In this paper, targeted retinal drug delivery with wireless magnetic microrobots is proposed. We focus on four fundamental issues involved in the development of such a system: biocompatible coating of magnetic microrobots, diffusion-based drug delivery, characterization of forces needed to puncture retinal veins, and wireless magnetic force generation. We conclude that targeted drug delivery with magnetic microrobots is feasible from an engineering perspective, and the idea should now be explored for clinical efficacy.

This paper presents the design of a multi-axis micro force-torque sensor. The sensor is able to measure forces along two axes and a torque perpendicular to these forces. The load is measured by capacitive comb drives which provide a high sensitivity. The microfabrication process, the sensor readout electronics as well as the calibration procedure are presented. The sensor was used to measure the force and torque on a magnetically actuated microrobot. This microrobot is assembled from microfabricated nickel parts for directed drug delivery inside the human body. Precise knowledge load on the microrobot is required for accurate positioning and control of the robot. The three-axis micro sensor is used to simultaneously measure the forces and torques acting on the microrobot in a magnetic field and thus provides valuable data for magnetic control methods of microrobots.