Based on the navigation strategy of insects utilizing the polarized skylight, an integrated polarization-dependent sensor for autonomous navigation is presented. The navigation sensor has the features of compact structure, high precision, strong robustness, and a simple manufacture technique. The sensor is composed by integrating a complementary-metal-oxide-semiconductor sensor with a multiorientation nanowire grid polarizer. By nanoimprint lithography, the multiorientation nanowire polarizer is fabricated in one step and the alignment error is eliminated. The statistical theory is added to the interval-division algorithm to calculate the polarization angle of the incident light. The laboratory and outdoor tests for the navigation sensor are implemented and the errors of the measured angle are ±0.02 deg and ±1.3 deg, respectively. The results show that the proposed sensor has potential for application in autonomous navigation.
For the direct measurement of microgripper gripping force and the calibration of microgripper jaw stiffness, this paper presents a new microforce measuring device based on low-cost SU-8 microcantilever sensors with integrated copper piezoresistive strain gauge. On the basis of the deduced equations, the geometric parameters of the microcantilever sensor are determined. Then, the fabrication of the sensors is carried out using a simple process. One fabricated sensor is calibrated by measuring the output voltage and the applied vertical force simultaneously. The calibration result of the microcantilever stiffness is 2.99 N/m and the output sensitivity is 0.51 V/N . The performance test results of the calibrated sensor show that the force sensing range is 405 μN and the maximum nonlinearity is 11 μN. Finally, the microgripping forces of two different microgrippers are measured by the developed device, and jaw stiffness calibrations are also carried out. According to the experiment results, the normally closed SU-8 microgripper has a jaw stiffness of ∼2.83 N/m and the jaw stiffness of the normally open SU-8 microgripper is ∼7.22 N/m .
Specimen alignment is critical for the accuracy and the reliability of micro-tensile testing. A vernier-groove carrier fabricated by bulk micromachining of silicon is developed. Through the vernier in the carrier the alignment accuracy can be detected, and the groove and the convex stands guarantee rapid alignment and high repeatability. In order to demonstrate the validity of the carrier, a micro-tensile specimen integrated with piezoresistive cells is designed. The specimen can detect axial alignment precision and tensile force simultaneously. The performances of the carrier and the specimen are tested by using a micro-tensile tester. By comparing the measured results of micro-tensile testing with the carrier and without the carrier, it is confirmed that high alignment precision and high repeatability can be obtained by the carrier. For the specimen, the sensitivity coefficient of the piezoresistive cells for tensile force measurement is equal to 0.017 mV/mN .
This work presents the mechanical characterization of SU-8 photoresists studied in the form of microscaled free-standing thin films with various effective length/width (aspect) ratios, achieved by a tensile testing method. Specimens were designed with gauge segments measuring 240 to 540 μm long and 40 to 80 μm wide with thickness fixed at 20 μm, all fabricated in the same processing conditions. The experiments were carried out on a microtensile testing system which had a load and displacement resolution of 0.25 mN and 10 nm, respectively. With a tensile loading speed of 0.02 μm/s, the average fracture strength of SU-8 photoresist was measured to be 66.34 MPa, and the calculated Young's modulus ranged from 0.86 to 2.33 GPa and the maximum strain from 1.02% to 9.70%, with variation dependent on the effective aspect ratio of the tested films. As a result, effective aspect ratio is concluded to be a significant factor mechanically charactering the size effect of SU-8 photoresist in microscale.
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