Achieving the Upper Bound of Piezoelectric Response in Tunable, Wearable 3D Printed Nanocomposites

Abstract

The trade-off between processability and functional responses presents significant challenges for incorporating piezoelectric materials as potential 3D printable feedstock. Structural compliance and electromechanical coupling sensitivity have been tightly coupled: high piezoelectric responsiveness comes at the cost of low compliance. Here, the formulation and design strategy are presented for a class of a 3D printable, wearable piezoelectric nanocomposite that approaches the upper bound of piezoelectric charge constants while maintaining high compliance. An effective electromechanical interphase model is introduced to elucidate the effects of interfacial functionalization between the highly concentrated perovskite nanoparticulate inclusions (exceeding 74 wt%) and light-sensitive monomer matrix, shedding light on the significant enhancement of piezoelectric coefficients. It is shown that, through theoretical calculation and experimental validations, maximizing the functionalization level approaches the theoretical upper bound of the piezoelectric constant d 33 at any given loading concentration. Based on these findings, their applicability is demonstrated by designing and 3D printing piezoelectric materials that simultaneously achieve high electromechanical sensitivity and structural functionality, as highly sensitive wearables that detect low pressure air (<50 Pa) coming from different directions, as well as wireless, self-sensing sporting gloves for simultaneous impact absorption and punching force mapping.barium titanate (BTO) [5] are the most frequently used piezoelectric ceramic materials for transducer applications. Direct 3D printing of piezoelectric-polymer composites offers a promising solution to fabricating complex piezoelectrics beyond conventional ceramic processing methods which require extensive, time-consuming sintering, may have residual porosity, and have brittle responses. However, due to the functionality-processability tradeoff, the resulting piezoelectric response of the printed nanocomposite is over two ordersof-magnitude lower than pure ceramic. [6] Increasing particle concentration leads to agglomeration, [7] high viscosity, [8] and significant light absorption, [9] making it difficult to manufacture fully complex microarchitectures or free form-factors. Additionally, the incompatibilities between high stiffness nanoparticle and low stiffness polymer, resulting in poor interfacial adhesion, [10] reduce stress transfer efficiency from the polymer matrix to the piezoelectric inclusions, and suppress the functional performance. Increasing the matrix stiffness was previously shown to be key to enhancing piezoelectric response, [11] but it remains unclear if highly-responsive flexible piezoelectric materials are possible.Recent studies have explored surface functionalization of a low concentration of BTO nanoparticles (below 2 vol%, i.e., 10 wt%) to covalently bind them to the polymer matrix, and have demonstrated appreciable enhancement of the piezoelectric coefficient 3D Printed Nanocomposi...

Progress in wearable electronics/photonics—Moving toward the era of artificial intelligence and internet of things

“…Tremendous information and commands can be defined by the combined operation of the 10 fingers, where the resultant interactive mode is simple and intuitive to perfectly match the logic of our brain. Many efforts have been carried out so far on the development of finger sensors and glove‐based HMIs for sensory information collection, for example, finger bending degrees, 111‐114 contact forces, 115‐117 friction during sliding, 118,119 and so on. Consequently, real‐time monitoring of hand motions can be achieved, showing the great prospect of building a dynamic interaction system between human and the virtual world.…”

“…In terms of hand/finger gesture based self‐powered HMIs, sensors based on the piezoelectric 111,116,260,261 and triboelectric 262‐264 transducing mechanisms have been extensively developed for soft wearable glove‐based electronics. Moreover, because of the wide choices of flexible and stretchable triboelectric materials, for example, metal, oxide, wood, fabric, rubber, and polymer, 265 many triboelectric‐based finger sensors have been developed recently, proving its great potential as self‐powered wearable HMIs.…”

Investigation and Attempt to 3D Print Piezoelectric 0-3 Composites Made of Photopolymer Resins and PZT

“…This study explores the possibility of using commercially available photopolymer resins instead of epoxies or polymers for the manufacturing of the 0-3 composites. It is believed that piezoelectric composites made of photopolymer can achieve the same or even higher piezoelectric outputs than piezoelectric composites made of other polymers or epoxies [1,2]. Photopolymer resins are a type of resins where polymerization is triggered with UV light and are most commonly used in Additive Manufacturing processes such as SLA and DLP [3].…”

“…Researchers already proved that both piezoelectric composites [1,2,[5][6][7][8][9] and piezoelectric solid ceramics [10][11][12][13][14][15][16] could be directly 3D printed with the stereolithography process. 3D printing provides a geometrical degree of freedom, which with proper designing [2] and chemical modification methods [7,9] allowing achieve extremely enhanced piezoelectric properties of flexible, 3D printed composites [1,7,9]. However, further understanding is still required to fully master the highly complex stereolithography process of suspensions made of photopolymers and ceramic inclusions.…”

“…Various PZT particle sizes, ranging from 5 µm [6] to as low as 220 nm [2] were investigated by the researchers at different ceramic loadings. Most researchers added up to 50 vol% of PZT [1,10,16] and succeeded in 3D printing of such suspensions. However, in most studies, researchers reported increasing the exposure time and UV-light intensity and at the same time 3D print thinner layers [5,6] or had to modify their machines to successfully 3D print high viscosity suspensions [1,2,8].…”