Flexible Tactile Sensor Using the Reversible Deformation of Poly(3-hexylthiophene) Nanofiber Assemblies

Abstract

In this letter, we report a simple approach to fabricating scalable flexible tactile sensors using a nanofiber assembly of regioregular poly(3-hexylthiophene) (P3HT). Uniform P3HT nanofibers are obtained through a continuous electrospinning process using a homogeneous solution of high-molecular-weight P3HT. The P3HT nanofibers are oriented by collecting them on a rotating drum collector. Small physical inputs into the self-standing P3HT nanofiber assemblies give rise to additional contact among neighboring nanofibers, which results in decreased contact resistance in directions orthogonal to the nanofiber orientation. The P3HT nanofiber assemblies could detect pressure changes and bending angles by monitoring the resistance changes, and the sensor responses were repeatable.

Recent advances in flexible sensors for wearable and implantable devices

“…60 Despite the versatility of polymer substrates, however, some inherent properties of polymers hinder the fabrication via conventional high-temperature processes with nanotube networks, nanoribbons, and nanomembranes. To overcome this problem, a number of low-temperature fabrication methods have been developed to stack inorganic NWs, including solution assembly, [49][50][51] Functional Layer for Programmable Active Matrices Typically, an OFET array has been frequently used as a switchable matrix in part because of its low-temperature processing and high flexibility. Also, a polymer microstructure has been integrated as a gate dielectric; this further strengthens the deformability and mechanosensitivity of the device.…”

“…10,11,46 To address some shortcomings of the current flexible devices, several innovative features have been incorporated into sensor systems, including transparency, 1,21 self-healing capabilities, 47 and energy harvesting [ Figure 1(d)]. 2 To achieve high flexibility in sensing devices, various fabrication methods are currently available with polymeric materials, as shown in Figure 2, such as low-temperature deposition, 48 solution processing, [49][50][51][52][53] transfer printing, 31,[54][55][56] and nanomolding/ micromolding. 2,[7][8][9]17 Typically, transistor arrays made of organic semiconductors or inorganic transferred nanomembranes/ribbons have been considered as key elements because of their defect-free layout, high-resolution processing, and superior carrier mobility.…”

Emerging flexible and wearable physical sensing platforms for healthcare and biomedical applications

“…Nevertheless, another class of flexible substrates, that is, soft silicone elastomers, such as polydimethylsiloxane (PDMS) and silicone rubbers 21 , is of great interest owing to providing additional advantages such as stretchability and compliancy 2 . Generally, physical sensing platforms operate based on relative variations in their electrical parameters, such as piezoelectricity [22][23][24] , triboelectricity 25,26 , capacitance [27][28][29][30] , or resistance [31][32][33] , to detect and quantify the desired physical data, including pressure and temperature. Depending on the types of active sensing elements experiencing these changes, these sensors may be largely classified into solid-state and liquid-state sensing devices.…”

“…As the name suggests, the active sensing element of the solidstate sensor is typically in solid form 3,[29][30][31][32] . Some examples include nanomaterials of polymers, carbon, semiconductors, and metals, for instance, carbon nanotubes (CNTs) [29][30][31]34,35 , semiconductor and metallic nanowires 3,36,37 , polymer nanofibers 23,24,32 , and metallic nanoparticles [38][39][40] . In contrast, physical sensors employing liquid active sensing components, such as ionic 41,42 and metallic liquids 43 , are classified as liquid-state sensors [41][42][43] .…”

A wearable and highly sensitive pressure sensor with ultrathin gold nanowires

“…To date, pressure sensors are typically based on forceinduced changes in capacitance 2,8,15,16 , piezoelectricity [17][18][19] , triboelectricity 7,13 and resistivity 20,21 . Recently, various nanomaterials, including nanowires 4,22,23 , carbon nanotubes 8,15,20 , polymer nanofibers 17,19,21,24 , metal nanoparticles [25][26][27] and graphene 28 have been used for the design of novel flexible pressure and strain sensors. The majority of these nanomaterialsbased pressure sensors are based on capacitance or piezoelectricity except for a few recent reports 20,21 , where resistivity was used for designing strain gauge sensors.…”