Design and Stiffness Analysis of a Bio-inspired Soft Actuator with Bi-direction Tunable Stiffness Property

The ability to modulate the stiffness of soft actuators plays a vital role in improving the efficiency of interacting with the environment. However, for the unidirectional stiffness modulation mechanism, high lateral stiffness and a wide range of bending stiffness cannot be guaranteed at the same time. Therefore, we draw inspiration from the anatomical structure of the finger, proposing a soft actuator with bi-direction tunable stiffness property (BTSA). BTSA is composed of air-tendon hybrid actuation (ATA) and bone-like structure (BLS). The bending stiffness can be tuned by ATA from 0.2 N/mm to 0.7 N/mm, about a magnification of 3.5 times. The lateral stiffness with BLS is enhanced up to 4.2 times compared to the one without BLS. Meanwhile the lateral stiffness can be tuned decoupling within a certain range of stiffness (e.g. from 0.35 N/mm to 0.46 when the bending angle is 45 deg). The BLS is designed according to a simplified stiffness analysis model. And a lost-wax based fabrication method is proposed to ensure the airtightness. The experiments about fingertip force, bending stiffness, and lateral stiffness are conducted to verify the property

A Bioinspired Bidirectional Stiffening Soft Actuator for Multimodal, Compliant, and Robust Grasping

The stiffness modulation mechanism for soft robotics has gained considerable attention to improve deformability, controllability, and stability. However, for the existing stiffness soft actuator, high lateral stiffness and a wide range of bending stiffness are hard to be provided at the same time. This paper presents a bioinspired bidirectional stiffening soft actuator (BISA) combining the air-tendon hybrid actuation (ATA) and a bone-like structure (BLS). The ATA is the main actuation of the BISA, and the bending stiffness can be modulated with a maximum stiffness of about 0.7 N/mm and a maximum magnification of 3 times when the bending angle is 45 deg. Inspired by the morphological structure of the phalanx, the lateral stiffness can be modulated by changing the pulling force of the BLS. The lateral stiffness can be modulated by changing the pulling force to it. The actuator with BLSs can improve the lateral stiffness about 3.9 times compared to the one without BLSs. The maximum lateral stiffness can reach 0.46 N/mm. And the lateral stiffness can be modulated decoupling about 1.3 times (e.g., from 0.35 N/mm to 0.46 when the bending angle is 45 deg). The test results show the influence of the rigid structures on bending is small with about 1.5 mm maximum position errors of the distal point of actuator bending in different pulling forces. The advantages brought by the proposed method enable a soft four-finger gripper to operate in three modes: normal grasping, inverse grasping, and horizontal lifting. The performance of this gripper is further characterized and versatile grasping on various objects is conducted, proving the robust performance and potential application of the proposed design method

Regrowth-free AlGaInAs MQW polarization controller integrated with sidewall grating DFB laser

We report an AlGaInAs multiple quantum well integrated source of polarization controlled light consisting of a polarization mode converter PMC, differential phase shifter(DPS), and a side wall grating distributed-feedback DFB laser. We demonstrate an asymmetrical stepped-height ridge waveguide PMC to realize TE to TM polarization conversion and a symmetrical straight waveguide DPS to enable polarization rotation from approximately counterclockwise circular polarization to linear polarization. Based on the identical epitaxial layer scheme, all of the PMC, DPS, and DFB laser can be integrated monolithically using only a single step of metalorganic vapor phase epitaxy and two steps of III V material dry etching. For the DFB-PMC device, a high TE to TM polarization conversion efficiency 98% over a wide range of DFB injection currents is reported at 1555 nm wavelength. For the DFB-PMC-DPS device, a 60 degree rotation of the Stokes vector was obtained on the Poincar\'e sphere with a range of bias voltage from 0 V to -4.0 V at IDFB is 170 mA.Comment: arXiv admin note: text overlap with arXiv:2210.1051

Stepped-height ridge waveguide MQW polarization mode converter monolithically integrated with sidewall grating DFB laser

We report the first demonstration of a 1555 nm stepped-height ridge waveguide polarization mode converter monolithically integrated with a side wall grating distributed-feedback (DFB) laser using the identical epitaxial layer scheme. The device shows stable single longitudinal mode (SLM) operation with the output light converted from TE to TM polarization with an efficiency of >94% over a wide range of DFB injection currents (IDFB) from 140 mA to 190 mA. The highest TM mode purity of 98.2% was obtained at IDFB=180 mA. A particular advantage of this device is that only a single step of metalorganic vapor-phase epitaxy and two steps of III-V material dry etching are required for the whole integrated device fabrication, significantly reducing complexity and cost

1.55-µm sidewall grating DFB lasers integrated with a waveguide crossing for an optical beam forming network

By using asymmetric twin-waveguide technology, a 1.55-μm sidewall grating distributed feedback laser monolithically integrated with a passive waveguide crossing was for the first time demonstrated for an optical beam forming network, which needs only one metalorganic vapor-phase epitaxy step. The distributed feedback laser with uncoated facets presents a side-mode suppression ratio of >44 dB and a low 3-dB linewidth of 68 kHz. An elliptical parabolic taper waveguide crossing had a theoretical crosstalk suppression ratio of 40 dB, while the measured cross-talk suppression ratio was at least 20 dB

Stepped-height ridge waveguide MQW polarization mode converter monolithically integrated with sidewall grating DFB laser

We report the first demonstration of a 1555 nm stepped-height ridge waveguide polarization mode converter monolithically integrated with a side wall grating distributed-feedback (DFB) laser using the identical epitaxial layer scheme. The device shows stable single longitudinal mode (SLM) operation with the output light converted from TE to TM polarization with an efficiency of >94% over a wide range of DFB injection currents (IDFB) from 140 mA to 190 mA. The highest TM mode purity of 98.2% was obtained at IDFB=180 mA. A particular advantage of this device is that only a single step of metalorganic vapor-phase epitaxy and two steps of III-V material dry etching are required for the whole integrated device fabrication, significantly reducing complexity and cost

Dual-wavelength DFB laser array based on sidewall grating and lateral modulation of the grating coupling coefficient

A monolithic dual-wavelength DFB laser array based on sidewall gratings and a novel modulation of the grating coupling coefficient is proposed and demonstrated experimentally. The grating coupling coefficient distribution along the cavity is modulated by changing the alignment between the gratings on the two sidewalls. The frequency difference between the two lasing modes can be modulated by changing the cavity length and grating recess depth. A series of microwave signals in the range of 50 GHz to 59 GHz is observed after beating the two optical lines in a photodetector. The measured optical linewidths are 250 kHz and 850 kHz when the cavity length is 1200 μm and 1000 μm, respectively

Spatial distribution, pollution, and health risk assessment of heavy metal in agricultural surface soil for the Guangzhou-Foshan urban zone, South China.

During the past decades, heavy metal pollution in agricultural soil and its impact on human health have been becoming one of the most important global environmental problems. In this research, heavy metal (Cu, Pb, Zn, Cr, Cd, Ni, As, Hg) concentrations were measured for four hundred and two soil samples collected from agricultural area within the Guangzhou-Foshan urban zone. Soil heavy metal pollution was evaluated used geoaccumulation index and potential ecological risk index. The dose response model proposed by the USEPA was used to estimate the potential health risk caused by heavy metals in agricultural soil. The results showed that: 1) Cd and Hg were the main heavy metal pollutants in agricultural soil of the study area. 89.1% and 93.3% of total soil samples suffered medium to heavy potential ecological risk caused by Cd and Hg, respectively. 2) The THI and TCR were respectively greater than 1.0 and 1.0×10-4, indicating that heavy metals in agricultural soil were likely to constitute non-carcinogenic and carcinogenic risks, both of which were mainly brought by product consumption, to the public in the study area. The non-carcinogenic risks were mainly caused by Cr and As, while the carcinogenic risks were mainly from Cr, Cd, and As