# Multi-Transduction-Mechanism Technology, an Emerging Approach to Enhance Sensor Performance

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Fundamental Transduction Sensing Mechanisms

#### 2.1. Piezoelectric Transduction

_{3}), zinc oxide (ZnO) and polyvinylidene difluoride (PVDF), and aluminum nitride (AlN) [9,14]. The electrical signal output of the piezoelectric sensor is given by Equation (1) [15], where $V$ is the voltage of the electrical signal output of the sensor, ${d}_{33}$ is the converse piezoelectric coefficient, $C$ is the capacitance, and $F$ is the applied pressure or mechanical change.

#### 2.2. Piezoresistive Transduction

#### 2.3. Capacitive Transduction

_{2}) [22]. For soft electronics, electrode materials are commonly made of carbon nanotubes, graphene, carbon powders, gold, and metal nanowires [22,23,24]. The governing equation for capacitance-based transducers is given in Equation (4), where $C$ is the capacitance of the transducer, $A$ is the overlapping area of the two electrodes, $d$ is the separation distance between the electrodes, ${\epsilon}_{o}$ is the space permittivity, and ${\epsilon}_{r}$ is the relative permittivity of the dielectric material [4].

#### 2.4. Electromagnetic Induction Transduction

_{3}, PVDF, and PZT [29,31]. The sensing principle of induction works by Faraday’s law in which an electromotive force is induced by a change in the magnetic flux [28]. For a static magnetic field, the induced electromotive force is shown in Equation (5) [28], where $\Psi $ is the induced electromotive force, $B$ is the magnetic flux density, and $S$ is the closed surface area of the induction coil.

#### 2.5. Triboelectric Transduction

^{2}to increase the ratio of collected charges per voltage unit [41]. The triboelectric materials with these properties include polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), and fluorinated ethylene propylene (FEP) [42].

## 3. Multi-Transduction Sensing Mechanisms

#### 3.1. Combined Piezoresistive–Piezoelectric Transduction

#### 3.2. Combined Capacitive–Piezoresistive Transduction

#### 3.3. Combined Capacitive–Piezoelectric Transduction

#### 3.4. Hybrid Nanogenerators

#### 3.4.1. Combined Triboelectric–Inductive Transduction

#### 3.4.2. Combined Piezoelectric–Triboelectric Transduction

^{−1}due to the high deformability of the triboelectric sensor compared to the piezoelectric sensor, whereas in the medium-pressure ranges, when both mechanisms work together, the sensitivity increases to 160 mV kPa

^{−1}[51].

#### 3.4.3. Combined Piezoelectric–Inductive Transduction

#### 3.5. Summary of Combined Transduction Mechanisms

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Schematic of a dual-transduction MEMS sensor employing piezoelectricity and piezoresistivity.

**Figure 2.**Working principle, design, and structural parameters of a capacitive–piezoresistive sensor for proximity and large pressure applications.

**Figure 4.**Schematic representation of TENG working modes. The relative motion between the triboelectric materials determines the mode of operation.

**Figure 5.**Working principle of a hybrid piezoelectric triboelectric nanogenerator based on a cantilever structure.

Combined Transduction Mechanisms | Key Parameters | Effect on Performance | Reference (s) |
---|---|---|---|

Piezoresistive–Piezoelectric | Resistance $R$, Voltage $V$ | Improved signal-to-noise ratio | [49] |

Capacitive–Piezoresistive Transduction | Capacitance $C$, Resistance $R$ | Long-distance proximity, large-range force detection | [11] |

Capacitive–Piezoelectric (DFUT) | CMUT frequency ${f}_{C}$, PMUT frequency ${f}_{P}$ | High resolution ($>200\mathsf{\mu}\mathrm{m}$), larger imaging depths ($>3\mathrm{cm}$) | [50] |

Triboelectric–Inductive | Charge $Q$, Separation distance between triboelectric layers $X$ | Harvest low-frequency energy in the range of [$1~100\mathrm{Hz}$] | [44,65] |

Piezoelectric–Triboelectric | Voltage $V$, Charge $Q$ | Detection at low [$0~50\mathrm{kPa}$] and medium [$50~120\mathrm{kPa}$] pressure ranges, Increased sensitivity to $160{\mathrm{mV}\text{}\mathrm{kPa}}^{-1}$ in the medium pressure ranges. | [51] |

Piezoelectric–Inductive | Piezoelectric power ${P}_{Piezo}$, Electromagnetic power ${P}_{EM}$ | Increased power to $40.62\mu \mathrm{W}$ for energy harvesting | [61] |

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**MDPI and ACS Style**

Elnemr, Y.E.; Abu-Libdeh, A.; Raj, G.C.A.; Birjis, Y.; Nazemi, H.; Munirathinam, P.; Emadi, A.
Multi-Transduction-Mechanism Technology, an Emerging Approach to Enhance Sensor Performance. *Sensors* **2023**, *23*, 4457.
https://doi.org/10.3390/s23094457

**AMA Style**

Elnemr YE, Abu-Libdeh A, Raj GCA, Birjis Y, Nazemi H, Munirathinam P, Emadi A.
Multi-Transduction-Mechanism Technology, an Emerging Approach to Enhance Sensor Performance. *Sensors*. 2023; 23(9):4457.
https://doi.org/10.3390/s23094457

**Chicago/Turabian Style**

Elnemr, Youssef Ezzat, Aya Abu-Libdeh, Gian Carlo Antony Raj, Yumna Birjis, Haleh Nazemi, Pavithra Munirathinam, and Arezoo Emadi.
2023. "Multi-Transduction-Mechanism Technology, an Emerging Approach to Enhance Sensor Performance" *Sensors* 23, no. 9: 4457.
https://doi.org/10.3390/s23094457