From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance.

We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices

Engineering miniaturized hair cell sensors for auditory system

© 2017 IEEE. Mechanosensory haircells are well-evolved biological sensors found in nature. In this paper, we present a novel artificial NEMS stereovilli sensor developed through novel fabrication techniques. The NEMS stereovilli sensor fabrication combines soft-polymer material synthesis methods and nanofiber generation techniques with conventional microfabrication methods to form novel flow sensors. The sensor fabrication mainly consists of three major steps which are 1) fabrication of artificial stereovilli of varying aspect ratios, 2) formation of nanofiber tip-links through electrospinning of PVDF material and 3) development of biomimetic HA-MA hydrogel cupula. These artificial sensors closely mimic stereovilli and achieve ultrahigh sensitivities through a biomimetic design. The sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively

Engineering biomimetic hair bundle sensors for underwater sensing applications

© 2018 Author(s). We present the fabrication of an artificial MEMS hair bundle sensor designed to approximate the structural and functional principles of the flow-sensing bundles found in fish neuromast hair cells. The sensor consists of micro-pillars of graded height connected with piezoelectric nanofiber "tip-links" and encapsulated by a hydrogel cupula-like structure. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. These biomimetic sensors achieve an ultrahigh sensitivity of 0.286 mV/(mm/s) and an extremely low threshold detection limit of 8.24 μm/s. A complete version of this paper has been published [1]

From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance

© The Author(s) 2016. We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices

Biomimetic hydrogel-CNT network induced enhancement of fluid-structure interactions for ultrasensitive nanosensors

Flexible, self-powered, miniaturized, ultrasensitive flow sensors are in high demand for human motion detection, myoelectric prosthesis, biomedical robots, and health-monitoring devices. This paper reports a biomimetic nanoelectromechanical system (NEMS) flow sensor featuring a PVDF nanofiber sensing membrane with a hydrogel infused, vertically aligned carbon nanotube (VACNT) bundle that mechanically interacts with the flow. The hydrogel-VACNT structure mimics the cupula structure in biological flow sensors and gives the NEMS flow sensor ultrahigh sensitivity via a material-induced drag force enhancement mechanism. Through hydrodynamic experimental flow characterization, this work investigates the contributions of the mechanical and structural properties of the hydrogel in offering a sensing performance superior to that of conventional sensors. The ultrahigh sensitivity of the developed sensor enabled the detection of minute flows generated during human motion and micro-droplet propagation. The novel fabrication strategies and combination of materials used in the biomimetic NEMS sensor fabrication may guide the development of several wearable, flexible, and self-powered nanosensors in the future.NRF (Natl Research Foundation, S’pore)Published versio