Abstract-We have micromachined a mechanical sensor that uses interferometry to detect the differential and absolute deflections of two adjacent cantilevers. The overall geometry of the device allows simple fluidic delivery to each cantilever to immobilize molecules for biological and chemical detection. We show that differential sensing is 50 times less affected by ambient temperature changes than the absolute, thus enabling a more reliable differentiation between specific cantilever bending and background effects. We describe the fabrication process and show results related to the dynamic characterization of the device as a differential sensor. The root-mean-squared (rms) sensor noise in water and air is 1 nm over the frequency range of 0.4-40 Hz. We also find that in air, the deflection resolution is limited only by the cantilever's thermomechanical noise level of 0.008 A Hz 1 2 over the frequency range of 40-1000 Hz.[781]

Human psychophysical experiments were designed and conducted to investigate the effect of 3D perspective visual images on the visual and haptic perception of size and stiffness in multimodal virtual environments (VEs). Virtual slots of varying length and buttons of varying stiffness were displayed to the subjects, who then were asked to discriminate their size and stiffness respectively using visual and/or haptic cues. The results of the size experiments show that under vision alone, farther objects are perceived to be smaller due to perspective cues and the addition of haptic feedback reduces this visual bias. Similarly, the results of the stiffness experiments show that compliant objects that are farther are perceived to be softer when there is only haptic feedback and the addition of visual feedback reduces this haptic bias. Hence, we conclude that our visual and haptic systems compensate for each other such that the sensory information that comes from visual and haptic channels is fused in an optimal manner.

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