[Show abstract][Hide abstract] ABSTRACT: Hydrodynamic imaging using the lateral line plays a critical role in fish behavior. To engineer such a biologically inspired sensing system, we developed an artificial lateral line using MEMS (microelectromechanical system) technology and explored its localization capability. Arrays of biomimetic neuromasts constituted an artificial lateral line wrapped around a cylinder. A beamforming algorithm further enabled the artificial lateral line to image real-world hydrodynamic events in a 3D domain. We demonstrate that the artificial lateral line system can accurately localize an artificial dipole source and a natural tail-flicking crayfish under various conditions. The artificial lateral line provides a new sense to man-made underwater vehicles and marine robots so that they can sense like fish.
Full-text · Article · Mar 2010 · Bioinspiration & Biomimetics
[Show abstract][Hide abstract] ABSTRACT: Almost all fish possess a flow-sensing system along their body, called the lateral line, that allows them to perform various behaviours such as schooling, preying, and obstacle or predator avoidance. Inspired from this, our group has built artificial lateral lines from newly-developed flow sensors using Micro-Electro-Mechanical Systems (MEMS) technology. To make our lateral line a functional sensory system, we develop an adaptive beamforming algorithm (applying Capon's method) that provides our lateral line with the capability of imaging the locations of oscillating dipoles in a 3D underwater environment. To help our sensor arrays adapt to the environment for better performance, we introduce a self-calibration algorithm that significantly improves the image accuracy. Finally, we derive the Cramer-Rao Lower Bound (CRLB) that represents the fundamental perfomance limit of our system and provides guidance in optimizing artificial lateral-line systems.
[Show abstract][Hide abstract] ABSTRACT: We report the development of an artificial hair cell (AHC) sensor with design inspired by biological hair cells. The sensor consists of a silicon cantilever beam with a high-aspect-ratio cilium attached at the distal end. Sensing is based on silicon piezoresistive strain gauge at the base of the cantilever. The cilium is made of photodefinable SU-8 epoxy and can be up to 700-mum tall. In this paper, we focus on flow-sensing applications. We have characterized the performance of the AHC sensor both in water and in air. For underwater applications, we have characterized the sensor under two flow conditions: steady-state laminar flow (dc flow) and oscillatory flow (ac flow). The detection limit of the sensor under ac flow in water is experimentally established to be below 1 mm/s. A best case angular resolution of 2.16deg is also achieved for the sensor's yaw response in air.
Preview · Article · Nov 2007 · Journal of Microelectromechanical Systems
[Show abstract][Hide abstract] ABSTRACT: A combined, hybrid soft-hard material design of a hair flow microsensor, which closely mimics the superficial neuromast of a blind cave fish with its superior ability to navigate blindly in a hydrodynamically complex underwater environment was introduced. The glycoprotein cupula couple the arrays of hairs to the surrounding environment maximizing and mediating drag forces along a moving body. A combination of haircell sensor with a hydrogel cupula grown by wet-chemistry micropatterned photopolymerization creates an integrated hair-cupula sensor with superior flow detection ability comparable with blind fish. This symbiotic technology is expected to enable the self-navigating ability of autonomous underwater vehicles. The enhanced protection afforded by the hydrogel encapsulated hair flow sensors should enhance their ability to withstand high elastic deformation due to impact as well as provide anticorrosive and antibiofouling properties to better withstand the marine environment.
Full-text · Article · Oct 2007 · Advanced Materials
[Show abstract][Hide abstract] ABSTRACT: We report the development and application of an artificial hair cell (AHC) flow sensor inspired by biological systems. With optimized design and fabrication process, the AHC is characterized in terms of sensitivity, calibration, and robustness. Especially, an AHC can discern variations of water flow down to 0.1mm/s and survive 55o deflections. The sensor has been applied to flow field measurements, matching perfectly with analytical and previous experimental results. By employing arrays of such AHC sensors, an artificial lateral line is constructed for biomimetic studies on localizing and tracking hydrodynamic events.
No preview · Article · Mar 2007 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract] ABSTRACT: We report the development and application of an artificial hair cell (AHC) flow sensor inspired by biological systems. With optimized design and fabrication process, the AHC is characterized in terms of sensitivity, calibration, and robustness. Especially, an AHC can discern variations of water flow down to 0.1 mm/s and survive 55deg deflections. The sensor has been applied to flow field measurements, matching perfectly with analytical and previous experimental results. By employing arrays of such AHC sensors, an artificial lateral line is constructed for biomimetic studies on localizing and tracking hydrodynamic events.
[Show abstract][Hide abstract] ABSTRACT: Nearly all underwater vehicles and surface ships today use sonar and vision for imaging and navigation. However, sonar and vision systems face various limitations, e.g., sonar blind zones, dark or murky environments, etc. Evolved over millions of years, fish use the lateral line, a distributed linear array of flow sensing organs, for underwater hydrodynamic imaging and information extraction. We demonstrate here a proof-of-concept artificial lateral line system. It enables a distant touch hydrodynamic imaging capability to critically augment sonar and vision systems. We show that the artificial lateral line can successfully perform dipole source localization and hydrodynamic wake detection. The development of the artificial lateral line is aimed at fundamentally enhancing human ability to detect, navigate, and survive in the underwater environment.
Preview · Article · Jan 2007 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: By mimicking fish lateral lines and fish sensing behaviors, we constructed an artificial lateral line and employed it for biomimetic flow sensing. Thirteen hot-film anemometers were mounted to the surface of a NACA0015 airfoil to constitute the artificial lateral line. The resulting fish-like platform was maneuvered by a 3-degree-of-freedom robotic arm for two-dimensional mobility in aquatic environments. Assisted with specially developed algorithms, two biologically relevant flow-sensing scenarios have been realized. They were tracking a nearby dipole source in still water by detecting the dipole flow field and tracking a distant stationary source in running water by detecting its hydrodynamic wake.
[Show abstract][Hide abstract] ABSTRACT: Artificial haircell (AHC) sensor is presented for highly sensitive flow-field measurements. Design considerations and MEMS process flows are given. Oscillating flow field measurements show sensitivity down to 0.6 mm/s flow rates, steady state flow fields detected down to 0.1 mm/s.
[Show abstract][Hide abstract] ABSTRACT: This work presents results towards realizing a flexible multimodal tactile sensing system for object identification. Using polymer substrates and simple fabrication, robust devices are made that can identify objects based on texture, temperature, as well as material properties such as hardness and thermal conductivity. These capabilities are possible using signal processing techniques and physical models along with individual sensing structures inspired by the specialization found in biological skin. These structures are used to sense various object parameters, and array-wide processing to identify texture using a Maximum Likelihood decision rule. 80% texture classification is achieved. In blind object identification tests, over 90% correct identification was achieved by measurement of material properties.
[Show abstract][Hide abstract] ABSTRACT: We report on the development of new elastomers and processes that utilize polymers such as PDMS, FSR (force sensitive resistor) polymer, MWCNT, and polyurethane to realize bioinspired sensors such as artificial haircells. In nature, haircell sensors are used by fish to sense flow, by spiders to sense vibration, and by some vertebrates for hearing and acoustics. An artificial haircell sensor is designed to mimic the ability of natural haircells to sense flow, vibration, and touch. However, in order to improve the sensitivity and robustness, the use of polymers is necessary. In this paper, we present the different generations of bioinspired artificial haircell sensors, along with the polymers and processes needed for their construction
[Show abstract][Hide abstract] ABSTRACT: We report characterization and application of recently developed, MEMS based, out-of-plane hot-wire anemometer (HWA) sensor and bio-inspired artificial hair cell (AHC) sensor. Sensitivities of 0.2mm/s for HWA and 0.1mm/s for AHC have been achieved in water flows, comparing with 1mm/s of a conventional HWA. In contrast to its high sensitivity, the AHC sensor can survive 55 bending of its hair, making it very robust. After calibration, both HWA and AHC sensors were employed for dipole field and wake measurements. The dipole field was generated by a vibrating sphere in a large water tank; the measurement results match very well with the analytical model. The wake was created by a circular cylinder in a water channel; the RMS velocity distributions replicate the main features of a typical wake accurately. The two types of sensors were also applied in array format to mimic a fish lateral line for imaging hydrodynamic events. Multi-modal sensors capable of simultaneous measurement of flow velocity, shear stress, pressure and temperature are under development.
[Show abstract][Hide abstract] ABSTRACT: We report the development of a high sensitivity artificial haircell (AHC) sensor that employs high aspect-ratio cilium (up to 700μm tall) made of SU-8 epoxy and silicon piezoresistive strain sensors. In this work, we demonstrate the application of the artificial haircell for underwater flow sensing. For device characterization, we have performed deflection testing, resonant frequency testing, sensitivity threshold testing and preliminary dipole field response experiments. We have demonstrated a flow rate sensitivity of 2mm/s.
[Show abstract][Hide abstract] ABSTRACT: PDMS (polydimethylsiloxane) elastomer is widely used in MEMS. However, PDMS is non-conductive and as a result is used in mostly structural applications. We report methods for monolithic integration of conductive and non-conductive PDMS for realizing wholly polymer-based devices with embedded elastomer wires, electrodes, heaters, and sensors. In this work we demonstrate elastomer strain gauges, capacitive pressure sensors, as well as microfluidic channels with integrated heaters and sensors. The process uses a series of PDMS patterning, micromolding, and bonding techniques with conductive PDMS features made by mixing with multiwall carbon nanotubes (MWNT).