Effect of Viscosity on the Formation of Porous Polydimethylsiloxane for Wearable Device Applications

Abstract

Medical devices, which enhance the quality of life, have experienced a gradual increase in demand. Various research groups have attempted to incorporate soft materials such as skin into wearable devices. We developed a stretchable substrate with high elasticity by forming a porous structure on polydimethylsiloxane (PDMS). To optimize the porous structure, we propose a manufacturing process that utilizes a high-pressure steam with different viscosities (400, 800, 2100, and 3000 cP) of an uncured PDMS solution. The proposed method simplifies the manufacturing of porous structures and is cost-effective compared to other technologies. Porous structures of various viscosities were formed, and their electrical and mechanical properties evaluated. Porous PDMS (3000 cP) was formed in a sponge-like three-dimensional porous structure, compared to PDMS formed by other viscosities. The elongation of porous PDMS (3000 cP) was increased by up to 30%, and the relative resistance changed to less than 1000 times with the maximum strain test. The relative resistance increased the initial resistance (R0) by approximately 10 times during the 1500-times repeated cycling tests with 30% strain. As a result, patch-type wearable devices based on soft materials can provide an innovative platform that can connect with the human skin for robotics applications and for continuous health monitoring.

Flexible capacitive pressure sensors with micro-patterned porous dielectric layer for wearable electronics

“…Over the years, polydimethylsiloxane (PDMS)-based silicone dielectric materials [31] have drawn wide visions owing to their favorable characteristics of flexibility [29,32], biocompatibility, and distinguished mechanical properties [7,13,33]. However, the sensors consisting of two electrodes sandwiching a PDMS dielectric layer usually displayed unqualified sensitivity, detection range, and fatigue durability, as previously reported [22,27].…”

“…In order to avoid the influences of air which was introduced at the earlier stirring process, the mold was placed on a horizontal bench for 30 min, and the air would escape from the mixture. During the 10 min of high-temperature treatment making pores, PDMS would cure rapidly, and the water molecules would evaporate from the mixture [33]. Meanwhile, positions occupied by water molecules would be vacated and do not collapse ever, which was benefited from the semi-cured PDMS after undergoing the high-temperature treatment.…”

“…The outstanding characteristics of this sensor were mainly benefited from the specific protruding surface micro-structure and the internal pores, according to the previously mentioned. On the one hand, the distance of the two electrodes would decrease dramatically when the sensor suffered from an external force [21,33,34]. On the other hand, the air in the pores would be squeezed out, and the relative permittivity of the whole dielectric layer would increase simultaneously since the much smaller dielectric constant of air than PDMS [7,10,35].…”

Micro-Sphere PDMS for Enhancing Light Extraction in Organic Light-Emitting Devices

“…These can be produced on a large scale and mass-produced, and the process is less restricted by equipment than other processes. Furthermore, polydimethylsiloxane (PDMS) has excellent formability because it has low surface energy [15]. Large-scale replica molding via the BF process can be applied to develop large-area light extraction films.…”

Photomechanical Polymer Nanocomposites for Drug Delivery Devices

“…Polydimethylsiloxane (PDMS) is a widely used polymer in different applications due to its remarkable thermal, mechanical, and biological properties [ 25 , 26 , 27 ]; its molecular structure is shown in Figure 1 . It can be further converted into a responsive polymer upon combining it with different micro- or nanoparticles [ 28 , 29 , 30 , 31 ].…”