The generation and sensation of mechanical force plays a role in many dynamic biological processes, including touch sensation. This paper presents a two-axis micro strain gauge force sensor constructed from multiple layers of SU-8 and metal on quartz substrates. The sensor was designed to meet requirements for measuring tactile sensitivity and interaction forces exerted during locomotion by small organisms such as the nematode Caenorhabditis elegans. The device is transparent and compatible with light microscopes, allowing behavioral experiments to be combined with quantitative force measurements. For the first time, we have characterized the scale of interaction forces generated in wild-type C. elegans in probing and responding to their environment during locomotion. The device features sub-μN force resolution from 1 Hz to 1 kHz, >25 μN range, kHz acquisition rates and biocompatibility.

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We present “molecular threading”, a surface independent tip-based method for stretching and depositing single and double-stranded DNA molecules. DNA is stretched into air at a liquid-air interface, and can be subsequently deposited onto a dry substrate isolated from solution. The design of an apparatus used for molecular threading is presented, and fluorescence and electron microscopies are used to characterize the angular distribution, straightness, and reproducibility of stretched DNA deposited in arrays onto elastomeric surfaces and thin membranes. Molecular threading demonstrates high straightness and uniformity over length scales from nanometers to micrometers, and represents an alternative to existing DNA deposition and linearization methods. These results point towards scalable and high-throughput precision manipulation of single-molecule polymers.

We developed a new process for laser-printing a thinfilm magnetic-polymer composite microstructural material directly onto planar silicon substrates and characterized its magnetic and mechanical properties. Using this technique we fabricated cantilever beams 100-2000μm long, 100-500μm wide, and 6-8μm thick. An external magnet was used to demonstrate actuation via magnetic field gradient forces, and a scanner was constructed able to deflect a laser beam 3˚. This technique takes advantage of advances in commercial laser printing technology and is suitable for low-cost, low-temperature, large-area MEMS devices and rapid MEMS fabrication on a variety of substrates.

This paper demonstrates using charge-biased vacuum encapsulated single-anchored double-ended tuning fork (DETF) resonators for humidity sensing. We charge-bias the DETF resonators and measure the change in the stored charge by observing the resonant frequency. Environmental humidity modifies the discharge characteristic of the resonator by varying the resistance between the bias bondpad and the surface silicon dioxide. Using this variation, we demonstrate a sensor that can determine relative humidity from <1 % to 60% with an absolute measurement uncertainty of less than ±0.8% RH.