Template‐Directed Growth of Hierarchical MOF Hybrid Arrays for Tactile Sensor

Abstract

Recently, conductive metal−organic frameworks (MOFs) as the active material have provided broad prospects for electronic device application. The positioning technologies for MOFs enable the fabrication of novel microstructures, which can modulate the morphology of the material and tune the properties for the targeted application. Herein, a template‐method is used to synthesize the hierarchical structure of MOF hybrid array (MHA) on copper mesh (MHA@Mesh) for flexible sensor. Finite element method (FEM) results indicate that the 3D hierarchical MHA@Mesh can mimic the micro/nanoscale structure of human skin, which enables an interlocking contact. MHA@Mesh‐based flexible sensor presents rapid response rate (<1 ms) and high sensitivity (up to 307 kPa−1) which is 20 times higher than that of MHA@Foil‐based sensor (15 kPa−1). The flexible pressure device could be applied to monitor the finger motion and human pulses. Moreover, the music recognition can be performed by integrating the MOFs hardware sensors with machine learning algorithms. Overall, this design concept of 3D hierarchical microarray structures demonstrates potential in the fields of wearable technologies and human–machine interfaces.

The Role of Metal–Organic Frameworks in Electronic Sensors

“…TheI 2 -TCA charge-transfer complex also moves the Fermi level toward the edge of the valance band, leading to oxidative doping of the framework with increased hole concentration in the band gap and subsequently increased conductivity and responsiveness to mechanical stimulus.When the structural framework shrinks through the mechanical force,the I 2 -TCA distance reduces to 6.38 at 4%strain level. Theshortened distance can increase the hopping probability and result in carrier mobility.T he accompanying decrease of the energy band gap (1.49 eV) upon deformation is also ascribed to the enhanced electronic communication between the adjacent I 2 -TCAcharge-transfer complexes.C onsequently,t he local deformation of MOF lattice would enhance the charge transport across the MOF nanofilm and induce strain-responsive conductivity of the sensor.T he practical measurements exhibited that the sensor could accurately recognize the different sport modes,including swaying, walking,a nd bicycling.R ecently,Z hou et al [83] also used at emplate method to synthesize the hierarchical structure of aMOF hybrid array (MHA) on acopper mesh as af lexible sensor.T he MHA mesh with 3D hierarchical architectures served as active component to sense the external pressure (Figure 10 h). Thes ignal-transduction mechanism is based on the numerous point-faces contacting between the MHA tips and Au/Cr thin film.…”

“…Reproducedw ith permission. [83] Copyright 2020 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim. Angewandte 2.5 %t o3 .3 %) which is suitable to recognize human body motions (Figure 10 e-g).…”

“…k) Current change with different finger bending angles. Reproducedw ith permission [83]. Copyright 2020 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim.…”

The Role of Metal–Organic Frameworks in Electronic Sensors

“…k) Current change with different finger bending angles. Reproduced with permission [83] . Copyright 2020 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim.…”

Micro‐Nano Processing of Active Layers in Flexible Tactile Sensors via Template Methods: A Review

“…micro-nano structure toward the sensing layer of the triboelectric tactile sensor, on the one hand, it gives the device better moisture resistance, which ensures the energy output efficiency; on the other hand, it greatly improves the effective contact area, increasing the friction charge density of the friction surface. [9,10] Consequently, researchers have explored micro-nano processing technology such as electrospinning, [11] magnetic-assisted method, [12] template method, [13] solution method, [14] 3D printing method, [15] and oblique-angle deposition method [16] to strengthen the sensing performance of tactile sensors. Thereinto, due to the advantages of high accuracy and reliability of the template method, it occupies a dominant position in the micro-nano processing and attracts many researchers' interest, which makes the rapid development of various templates and gradually forms a trend of "contention among a hundred schools of thought".…”