G.J.M. Krijnen’s research while affiliated with University of Twente and other places

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Publications (255)


Fig. 1. Schematic representation of the geometry of the artificial hair sensor together with its biological source of inspiration. 1
Fig. 2. 3-D schematic, condensed representation of the fabrication process of the artificial hair sensor [22].
Fig. 4. Block diagram representing the biomimetic principle of the cricket-spider attack process.
Fig. 5. Schematic representing the dipole-source artificial hair sensor geometry. Theoretical (solid) and squeezed (dashed) streamlines are drawn for clarification.
Fig. 8. Photograph showing the setup of the transient response measurements with a close-up view of the single-chip artificial hair sensor array together with the piston shaft. 3 The DDS system represents the direct digital synthesis system.

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Mimicking the Flow Signature of Running Spiders by Utilizing Bio-Inspired Hair Sensors Targeting Spatiotemporal Airflow Mapping
  • Article
  • Full-text available

August 2023

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55 Reads

IEEE Sensors Journal

Ahmad M. Dagamseh

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Gijs M. Krijnen

In nature, insects equipped with hair sensors can provide valuable information through the patterns generated by airflow sources. In this paper, we modeled and measured the transient response of an artificial hair sensor, which imitates the attack sequence of a spider-cricket in nature. The results indicate a strong correlation between the shape of the measured airflow fields and the shape of the dipole airflow field. The hair sensor is capable of tracking the characteristics of the airflow field with sufficient spatiotemporal resolution. As a demonstration of the feasibility of measuring spatiotemporal airflow patterns using high-density arrays of hair sensors, the dipole flow field obtained is utilized to predict the position of the dipole source. There is good agreement between the estimated distance and the physically set distance of the dipole source. This represents a significant step towards demonstrating the feasibility of a high-resolution "airflow camera" that utilizes artificial hair airflow sensors.

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A Peristaltic Micropump Based on the Fast Electrochemical Actuator: Design, Fabrication, and Preliminary Testing

March 2021

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264 Reads

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12 Citations

Actuators

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Gijs J. M. Krijnen

Microfluidic devices providing an accurate delivery of fluids at required rates are of considerable interest, especially for the biomedical field. The progress is limited by the lack of micropumps, which are compact, have high performance, and are compatible with standard microfabrication. This paper describes a micropump based on a new driving principle. The pump contains three membrane actuators operating peristaltically. The actuators are driven by nanobubbles of hydrogen and oxygen, which are generated in the chamber by a series of short voltage pulses of alternating polarity applied to the electrodes. This process guaranties the response time of the actuators to be much shorter than that of any other electrochemical device. The main part of the pump has a size of about 3 mm, which is an order of magnitude smaller in comparison with conventional micropumps. The pump is fabricated in glass and silicon wafers using standard cleanroom processes. The channels are formed in SU-8 photoresist and the membrane is made of SiNx. The channels are sealed by two processes of bonding between SU-8 and SiNx. Functionality of the channels and membranes is demonstrated. A defect of electrodes related to the lift-off fabrication procedure did not allow a demonstration of the pumping process although a flow rate of 1.5 µl/min and dosage accuracy of 0.25 nl are expected. The working characteristics of the pump make it attractive for the use in portable drug delivery systems, but the fabrication technology must be improved.


Correction to ‘A biomimetic accelerometer inspired by the cricket's clavate hair’

November 2020

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24 Reads


Figure 12. The estimated diffusion coefficient (red dots) and 1σ confidence interval as a function of the inverse square root of the number of trajectories (N).
A Thermodynamic Description of Turbulence as a Source of Stochastic Kinetic Energy for 3D Self‐Assembly

July 2019

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141 Reads

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12 Citations

The extent to which one can use a thermodynamic description of turbulent flow as a source of stochastic kinetic energy for 3D self‐assembly of magnetically interacting macroscopic particles is investigated. It is confirmed that the speed of the objects in the flow field generated in this system obeys the Maxwell–Boltzmann distribution, and their random walk can be defined by a diffusion coefficient following from the Einstein relation. However, it is discovered that the analogy with Brownian dynamics breaks down when considering the directional components of the velocity. For the vectorial components, neither the equipartition theorem nor the Einstein relation is obeyed. Moreover, the kinetic energy estimated from the random walk of individual objects is one order of magnitude higher than the value estimated from Boltzmann statistics on the interaction between two spheres with embedded magnets. These results show that introducing stochastic kinetic energy into a self‐assembly process by means of turbulent flow can to a great extent be described by standard thermodynamic theory, but anisotropies and the specific nature of the interactions need to be taken into account.


FIG. 5: The estimated diffusion coefficient (red dots) and 1σ confidence interval as a function of the inverse square root of the number of trajectories (N).
A thermodynamic description of turbulence as a source of stochastic kinetic energy for 3D self-assembly

June 2019

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126 Reads

We investigate to what extent one can use a thermodynamic description of turbulent flow as a source of stochastic kinetic energy for three-dimensional self-assembly of magnetically interacting macroscopic particles. We confirm that the speed of the objects in the flow field generated in our system obeys the Maxwell--Boltzmann distribution, and their random walk can be defined by a diffusion coefficient following from the Einstein relation. However, we discovered that the analogy with Brownian dynamics breaks down when considering the directional components of the velocity. For the vectorial components, neither the equipartition theorem, nor the Einstein relation is obeyed. Moreover, the kinetic energy estimated from the random walk of individual objects is one order of magnitude higher than the value estimated from Boltzmann statistics on the interaction between two spheres with embedded magnets. These results show that introducing stochastic kinetic energy into a self-assembly process by means of turbulent flow can to a great extent be described by standard thermodynamic theory, but anisotropies and the specific nature of the interactions need to be taken into account.


Insect-Inspired Distributed Flow-Sensing: Fluid-Mediated Coupling Between Sensors

January 2019

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465 Reads

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6 Citations

Springer Series in Materials Science

Crickets and other arthropods are evolved with numerous flow-sensitive hairs on their body. These sensory hairs have garnered interest among scientists resulting in the development of bio-inspired artificial hair-shaped flow sensors. Flow-sensitive hairs are arranged in dense arrays, both in natural and bio-inspired cases. Do the hair-sensors which occur in closely-packed settings affect each other’s performance by so-called viscous coupling? Answering this question is key to the optimal arrangement of hair-sensors for future applications. In this work viscous coupling is investigated from two angles. First, what does the existence of many hairs at close mutual distance mean for the flow profiles? How is the air-flow around a hair changed by it’s neighbours proximity? Secondly, in what way do the incurred differences in air-flow profile alter the drag-torque on the hairs and their subsequent rotations? The first question is attacked both from a theoretical approach as well as by experimental investigations using particle image velocimetry to observe air flow profiles around regular arrays of millimeter sized micro-machined pillar structures. Both approaches confirm significant reductions in flow-velocity for high density hair arrays in dependence of air-flow frequency. For the second set of questions we used dedicated micro-fabricated chips consisting of artificial hair-sensors to controllably and reliably investigate viscous coupling effects between hair-sensors. The experimental results confirm the presence of coupling effects (including secondary) between hair-sensors when placed at inter-hair distances of less than 10 hair diameters (d). Moreover, these results give a thorough insight into viscous coupling effects. Insight which can be used equally well to further our understanding of the biological implications of high density arrays as well as have a better base for the design of biomimetic artificial hair-sensor arrays where spatial resolution needs to be balanced by sufficiently mutually decoupled hair-sensor responses.


Embedded sensing: Integrating sensors in 3-D printed structures

March 2018

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2,715 Reads

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79 Citations

Journal of Sensors and Sensor Systems

Current additive manufacturing allows for the implementation of electrically interrogated 3-D printed sensors. In this contribution various technologies, sensing principles and applications are discussed. We will give both an overview of some of the sensors presented in literature as well as some of our own recent work on 3-D printed sensors. The 3-D printing methods discussed include fused deposition modelling (FDM), using multi-material printing and poly-jetting. Materials discussed are mainly thermoplastics and include thermoplastic polyurethane (TPU), both un-doped as well as doped with carbon black, polylactic acid (PLA) and conductive inks. The sensors discussed are based on biopotential sensing, capacitive sensing and resistive sensing with applications in surface electromyography (sEMG) and mechanical and tactile sensing. As these sensors are based on plastics they are in general flexible and therefore open new possibilities for sensing in soft structures, e.g. as used in soft robotics. At the same time they show many of the characteristics of plastics like hysteresis, drift and non-linearity. We will argue that 3-D printing of embedded sensors opens up exciting new possibilities but also that these sensors require us to rethink how to exploit non-ideal sensors.



A 2D Particle Velocity Sensor With Minimal Flow Disturbance

December 2016

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58 Reads

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13 Citations

IEEE Sensors Journal

A 2D sound particle velocity sensor, consisting of a cross of two connected, heated wires is presented. We developed a fabrication process by which the wires become freely suspended 350 mu m above the chip surface. This largely eliminates the influence of boundary layer effects and increases the temperature gradient along the wires, both due to the large distance to the silicon substrate. As a result, the sensor has increased sensitivity and reduced power consumption compared with an earlier design. Furthermore, due to the fully symmetrical structure of the sensor, the sensitive directions are exactly orthogonal to each other and have near identical sensitivity, thus requiring no individual calibration.


Recent Developments in Bio-Inspired Sensors Fabricated by Additive Manufacturing Technologies

October 2016

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31 Reads

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2 Citations

Advances in Science and Technology

In our work on micro-fabricated hair-sensors, inspired by the flow-sensitive sensors found on crickets, we have made great progress. Initially delivering mediocre performance compared to their natural counter parts they have evolved into capable sensors with thresholds roughly a factor of 30 larger than of their natural equivalents. Due to this disparity, and also instigated by our work on fly-halteres inspired rotation rate sensors and desert locust ear-drum mimicking membrane struc- tures, we have analysed the differences in performance between natural and man-made sensors. We conclude that two major drawbacks of main-stream micro-fabrication are the lack of easily applicable soft materials, as well as the limitations imposed by photolithography based fabrication with respect to freeform 3D shaping of structures. Currently we are targeting additive manufacturing for biomimetic sensor structures and in this contribution we report initial results of 3D printed sensor structures.


Citations (66)


... The desired size of the sensor is 1 cm × 1 cm, with minimal thickness to reduce the influence of the sensor on the measurement. The demands on sensor size and force range initiated the development of our previously presented force sensors [28,29]. These sensors showed good sensitivity for normal forces and moments, but the shear force sensitivity of the sensor in [29] was relatively low. ...

Reference:

Miniature large range multi-axis force-torque sensor for biomechanical applications
Six-axis force–torque sensor with a large range for biomechanical applications

... Active fluid manipulation systems implement external forces to direct fluid flow and thus offer more flexibility over the flow rate control compared to passive pumps. Several types of active microfluidic pumps have been developed employing various external means including mechanical actuators and magnetic, electric, acoustic, and optical fields [21][22][23][24][25]. Mechanically actuated micropumps including various types of peristaltic devices have been used in different forms to achieve controlled fluid pumping on a small scale [26,27]. These devices generally feature a flexible poly(dimethylsiloxane) (PDMS) layer and directional flow resistance to obtain a net flow rate [28]. ...

A Peristaltic Micropump Based on the Fast Electrochemical Actuator: Design, Fabrication, and Preliminary Testing

Actuators

... supplied to the solution, in which case agitation must be provided in a more controlled manner by a machine 35 . Third, our demonstration was conducted using a solder with a melting temperature of 60 °C, which may be too low for commercial MicroLED displays. ...

A Thermodynamic Description of Turbulence as a Source of Stochastic Kinetic Energy for 3D Self‐Assembly

... Man-made systems are likewise highly constrained, though sensor sparsity may be more critical in these than in nature. Sparsity is driven by size, weight, and power reduction, potential viscous coupling problems, control actuator design, and structural considerations [12,13], especially at the micro-or small-UAS scale. Therefore, selecting optimal locations for a given budget of flow sensors is a primary challenge for designing FBF-enabled aircraft. ...

Insect-Inspired Distributed Flow-Sensing: Fluid-Mediated Coupling Between Sensors

Springer Series in Materials Science

... The Material Extrusion (MEX) process, defined by ISO/ASTM 52900 as the process in which materials are selectively dispensed through a nozzle or orifice, has been extensively used for the extrusion of conductive materials in order to manufacture electrical sensors [1,2] that can be easily embedded into dielectric structure during the MEX process [3]. However, the widely seen issues pertaining to quality and repeatability of mechanical performance seen in MEX samples [4], also translate to unpredictable performance issues in electrical sensors manufactured using MEX processes. ...

Embedded sensing: Integrating sensors in 3-D printed structures

Journal of Sensors and Sensor Systems

... Insects have evolved multiple sensors to interact with their environment. Here again, the 3D-shape of the sensors can have a profound importance and, thus, AM could be an efficient tool to investigate or reproduce biosensors [50]. ...

Recent Developments in Bio-Inspired Sensors Fabricated by Additive Manufacturing Technologies
  • Citing Article
  • October 2016

Advances in Science and Technology

... Other types of AVSs, such as thermal-based AVSs [12][13][14] and hair-based AVSs [15], are directly sensitive to the firstorder acoustic particle velocity; therefore, the directionality of these sensors is frequency-independent. Compared with the hair-based AVS, the thermal-based AVS makes it easier to integrate a multi-sensitive axis on a chip and the signal readout circuit is simpler [16,17]. The thermal-based AVS is composed of two or three suspended platinum wires, which is similar to hot-wire anemometry. ...

A 2D particle velocity sensor with minimal flow-disturbance
  • Citing Conference Paper
  • November 2015

... The thermal convection-based acoustic vector sensor was first proposed in the late 1990s. 1 It has been applied in various tasks such as sound source localization, near-field holography, and sound intensity measurement. 2 The vector sensor can directly measure the acoustic particle velocity and have an intrinsically directional response to the incident sound waves. It usually consists of two closely spaced silicon nitride wires with a platinum layer on top of them. ...

A 2D Particle Velocity Sensor With Minimal Flow Disturbance
  • Citing Article
  • December 2016

IEEE Sensors Journal

... In the 2D model the heater had a fixed temperature condition while the left and right edges were assigned as a Perfectly Matched Layer (PML) condition which establish anechoic termination (no reflections) to assure propagative plane waves. The ΔT is proportional to the sensitivity of the device and it depends strongly on the geometric configuration of the filaments [3] [7][8]. Several configurations as the filament separation (a), width (wf) and thickness (he), were evaluated to analyse the influences in the frequency response. ...

A 2D acoustic particle velocity sensor with perfectly orthogonal sensitivity directions
  • Citing Article
  • May 2016

Sensors and Actuators A Physical

... The tested hydrophone illustrates a sensitivity of −200 dB in the frequency below 800 Hz, and a regular figure of eight pattern is shown in the direction experiment. Krijnen et al. introduced a biomimetic flow sensor for environmental awareness in [17]. The input acceleration is detected by measuring the differential capacitance shift. ...

Biomimetic flow sensors for environmental awareness

Proceedings of meetings on acoustics Acoustical Society of America