Polydimethylsiloxane Sponge Research Articles

Smart and responsive nano copper oxide–PDMS composite for “three-in-one” synergistic adsorptive–oxidative / reductive degradation of the persistence of organic pollutants, elimination of nanoparticles and heavy metal ion

Copper-and silica-based materials have been used globally as environmental catalysts and adsorbents for centuries. Despite their differences in their properties and roles in the participation of environmental activity, both have been combined to create various types of functional materials, ranging from copper oxides and polydimethylsiloxane (PDMS) sponge (PS) cores to advanced hybrid composite materials. In this work, CuO was incorporated onto SiO2 (CPC) by calcination of PDMS-Cu2O sponge, and the physicochemical properties and application of CPC were investigated. The CPC was homogeneous in a surface area (326.69 m2g-1), pore size (33.16 Å), pore volume (0.056 cm³g−1), and particle size (183.66 Å). This CPC has been used for the degradation (oxidation/reduction) and adsorption of azithromycin (AZM), 1,4-dichlorobenzene (DCB), rhodamine B (RB), methylene blue (MB), 4-nitrophenol (4-NP), gold nanoparticles (AuNPs), and chromium (VI). Efficiencies of CPC for the above persistence of organic pollutants (POPs) and adsorption of AuNPs and Cr(VI) were ∼72–100% under optimized conditions. CPC followed the pseudo-second-order (PSO) degradation kinetics with a higher r2 (>0.99) with eight cycles of reusability. Moreover, this synthetic strategy can be tailored to produce nanostructured composite materials and/or those associated with other species for diverse environmental and industrial applications.

Capacitive flexible pressure sensor based on porous GR/PDMS composite dielectric layer

Capacitive flexible pressure sensors, with the advantages of simple structure, reliable repeatability, and low energy consumption, have been widely used in wearable devices, soft robots, and other fields. This article describes the preparation of a polydimethylsiloxane (PDMS) sponge dielectric layer with a surface microstructure and dense internal bubbles by adding ammonium bicarbonate to PDMS, using sandpaper as a template, and utilizing the thermal decomposition of ammonium bicarbonate into three gases: ammonia, carbon dioxide, and water vapor (NH3, CO2, and H2O). Meanwhile, the sensitivity of the capacitive flexible pressure sensor using the sandwich structure with PDMS sponge can reach 0.4321 kPa−1 within the range of 0–3 kPa, and it has a fast response time and recovery time, good repeatability, and a wide detection range. The pressure sensor based on a porous graphene/PDMS (GR/PDMS) sponge dielectric layer can achieve human physiological signal detection and has broad application prospects in fields such as robot skin.

Highly compressible wearable sensor with CNT-coated PDMS sponge electrodes for tactile monitoring application

Electrical resistance-based sensors have attracted great attention due to their wide range of applications, among which sensors for detecting external forces are indispensable due to the complex environment of the modern era. Inspired by the capillary phenomenon, in this study, we fabricated a carbon nanotube (CNT)-polydimethylsiloxane (PDMS)-based compressive resistive sensor that is easy to fabricate and has a wide range of sensitivities. Repeated compression tests were performed to evaluate the durability of the fabricated sensors. Different coating conditions resulted in different durability depending on the extent to which the CNT electrodes were coated on the porous PDMS surface, and the sensitivity of the sensors could be controlled by CNT concentration, coating time, and coating depth. Resistive sensors with different sensitivities can easily detect changes in electrical signals due to finger pressure, which shows great promise for use in wearable electronics. In addition, the resistive sensor is biocompatible because only the pure PDMS surface is attached to the human body, and the porous structure exhibits good compressibility.

Marine biomass-derived PDMS-based composite sponge for sustainably sourced solar-driven interfacial evaporation

Solar-driven interface evaporation has emerged as an attractive technology for addressing the pressing issue of water scarcity. Herein, from the perspective of utilizing and managing ocean resources, we have developed a comprehensive evaporator based on ocean biomass for efficient solar-driven interfacial evaporation, aiming to sustainably harness marine resources. The construction of a biomass-based evaporator was achieved using three-dimensional melanin nanoparticles (MNPs)@carboxymethyl chitosan (CMCS)/polydimethylsiloxane (PDMS) porous sponge, which exhibits highly hydrophilic and porous properties. In this study, MNPs functioned as the photothermal material and the CMCS-hydrophilic modified PDMS sponge was utilized as the supportive material. Owing to its outstanding photothermal conversion capability and ingeniously designed columnar shape with cold evaporation surface, the MCP sponge-based evaporator achieves a water evaporation rate of 2.04 kg·m−2·h−1 and an evaporation efficiency of 85% under 1sun illumination. In addition, the MCP sponge-based evaporator exhibits an outstanding desalination performance (93% salt rejection) and purification efficiency for dyes with natural sunlight. This groundbreaking study presents an innovative method by utilizing marine biomass-derived CMCS and MNPs as raw materials to construct a high-performance solar-driven interface evaporator, thereby tackling clean water generation and promoting the sustainability of marine ecosystems.

Preparation of La-doped ZnFe LDH immobilized on polydimethylsiloxane sponge for the peroxymonosulfate-assisted photocatalytic degradation of rifampicin

In this study, La-doped ZnFe layered double hydroxide (La-ZnFe LDH) was immobilized on polydimethylsiloxane (PDMS) sponges and applied in the photocatalytic degradation process for the activation of peroxymonosulfate (PMS). The La-ZnFe LDH, PDMS sponge, and PDMS@La-ZnFe LDH samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FT-IR) analyses, and contact angle goniometer. The immobilized catalyst had a porous structure with a specific surface area of 5.94 m2 g−1 and a pore volume of 1.36 cm3 g−1. The PDMS@La-ZnFe LDH has the high potential to degrade rifampicin by activating PMS with a notable synergistic factor of 3.38. The optimum operating conditions for the degradation of 15 mg L−1 of rifampicin were determined as 0.2 mmol L−1 of PMS, 100 W of light intensity, and pH of 8, conducting the degradation efficiency to 92.8% within 360 min. According to the radical quenching tests, h+, •OH, SO4•−, and O2•− exhibited an important role in the rifampicin degradation. Besides, the PDMS@La-ZnFe LDH sponge possessed excellent reusability during the PMS-activated photocatalytic process after seven consecutive runs. Furthermore, the treatment of rifampicin from real wastewater was also evaluated. GC-MS analysis was carried out to determine the generated by-products during the photocatalytic degradation process. Briefly, La-ZnFe LDH catalyst immobilized with PDMS sponges can be a promising reusable and durable photocatalyst for the degradation of refractory organic pollutants.

Development of highly sensitive/durable porous carbon nanotube–polydimethylsiloxane sponge electrode for wearable human motion monitoring sensor

Herein, we present a novel approach for fabricating porous carbon nanotube–polydimethylsiloxane (CNT–PDMS) sponge electrodes for piezoelectric/piezoresistive sensing.

Superhydrophobic pressure-responsive pressure sensors based on an inner–outer synergistic conductive network of GAF/PDMS

We used a simple method to prepare a superhydrophobic pressure-sensitive sensor based on the internal and external synergistic conductive networks of graphene fragments and polydimethylsiloxane sponges.

MXene/PPy@PDMS sponge-based flexible pressure sensor for human posture recognition with the assistance of a convolutional neural network in deep learning

The combination of flexible sensors and deep learning has attracted much attention as an efficient method for the recognition of human postures. In this paper, an in situ polymerized MXene/polypyrrole (PPy) composite is dip-coated on a polydimethylsiloxane (PDMS) sponge to fabricate an MXene/PPy@PDMS (MPP) piezoresistive sensor. The sponge sensor achieves ultrahigh sensitivity (6.8925 kPa−1) at 0–15 kPa, a short response/recovery time (100/110 ms), excellent stability (5000 cycles) and wash resistance. The synergistic effect of PPy and MXene improves the performance of the composite materials and facilitates the transfer of electrons, making the MPP sponge at least five times more sensitive than sponges based on each of the individual single materials. The large-area conductive network allows the MPP sensor to maintain excellent electrical performance over a large-scale pressure range. The MPP sensor can detect a variety of human body activity signals, such as radial artery pulse and different joint movements. The detection and analysis of human motion data, which is assisted by convolutional neural network (CNN) deep learning algorithms, enable the recognition and judgment of 16 types of human postures. The MXene/PPy flexible pressure sensor based on a PDMS sponge has broad application prospects in human motion detection, intelligent sensing and wearable devices.

Non-Aqueous Poly(dimethylsiloxane) Organogel Sponges for Controlled Solvent Release: Synthesis, Characterization, and Application in the Cleaning of Artworks.

Polydimethylsiloxane (PDMS) organogel sponges were prepared and studied in order to understand the role of pore size in an elastomeric network on the ability to uptake and release organic solvents. PDMS organogel sponges have been produced according to sugar leaching techniques by adding two sugar templates of different forms and grain sizes (a sugar cube template and a powdered sugar template), in order to obtain materials differing in porosity, pore size distribution, and solvent absorption and liquid retention capability. These materials were compared to PDMS organogel slabs that do not contain pores. The sponges were characterized by Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and compared with PDMS slabs that do not contain pores. Scanning electron microscopy (SEM) provided information about their morphology. X-ray micro-tomography (XMT) allowed us to ascertain how the form of the sugar templating agent influences the porosity of the systems: when templated with sugar cubes, the porosity was 77% and the mean size of the pores was ca. 300 μm; when templated with powdered sugar, the porosity decreased to ca. 10% and the mean pore size was reduced to ca. 75 μm. These materials, porous organic polymers (POPs), can absorb many solvents in different proportions as a function of their polarity. Absorption capacity, as measured by swelling with eight solvents covering a wide range of polarities, was investigated. Rheology data established that solvent absorption did not have an appreciable impact on the gel-like properties of the sponges, suggesting their potential for applications in cultural heritage conservation. Application tests were conducted on the surfaces of two different lab mock-ups that simulate real painted works of art. They demonstrated further that PDMS sponges are a potential innovative support for controlled and selective cleaning of works of art surfaces.

Evaluating the potential of MesoporousTiO2/ NiFe2O4 nano composite integrated on polydimethylsiloxane sponge for degradation of Methyl Orange

Evaluating the potential of MesoporousTiO2/ NiFe2O4 nano composite integrated on polydimethylsiloxane sponge for degradation of Methyl Orange

Three-dimensional hydrophobic melamine@methyl trichlorosilane/polydimethylsiloxane sponge for consecutive and long-term oil/water separation

Herein, a melamine sponge is adopted as the skeleton to be modified by both methyl trichlorosilane (MTS) and polydimethylsiloxane (PDMS) on the surface, fabricating the 3D porous Mel@MTS/PDMS sponge. Systemic investigations reveal that MTS self-assembles into many micro-nano particles to roughen the surface of the melamine matrix, thus greatly increasing its hydrophobicity. PDMS tightly anchors those MTS particles via forming a surface coating. Therefore, the resultant Mel@MTS/PDMS sponge exhibits the superior oil-adsorbed capacity, good hydrophobicity, and great structural and mechanical stability. Based on this Mel@MTS/PDMS sponge, a consecutive oil/water separation system is successfully built and induces the continuous recovery of oil under various simulated oil–water separation conditions. Obviously, this 3D hydrophobic Mel@MTS/PDMS sponge and corresponding consecutive oil/water separation device provide a promising application strategy in the leaked oil recovery and environmental purification.

(Invited) inkjet-Printed Soft Electronic Devices and Sensors for Wearable Health Monitoring Applications

Stretchable electronic devices and sensors built on thin elastomer substrates may find a wide range of applications in wearable health monitoring devices owing to their ability to conformably adapt to human skin for long-term and comfortable wearing. In this talk, I will present our work on developing intrinsically-stretchable electronic materials that are formulated as electronic inks and patterend using a highly scalable and low-cost inkjet printing process. A variety of soft sensors including silver nanoparticle based ultrasensitive resistive strain sensor and pressure sensor, porous elastomer dielectric based capacitive pressure sensor, and multimodal sensor that can differentiate pressure, strain, and temperature stimuli have all been demonstrated on ultrathin polydimethylsiloxane (PDMS) substrate by printing. These devices have been used in applications including motion and gesture tracking, voice recognition, arterial pulse waveform and photoplethysmogram monitoring. In addition, I will also report our work on the development of a unique porous PDMS sponge electrode as a gel-free dry interface for motion-artifact tolerant recording of electrophysiological signals. The porous structure of the soft electrode significantly increases the effective contact area and lowers the electrode-skin impedance, which result in improved signal-to-noise ratio. Compared to commercial rigid electrodes, the soft and thin form factor also makes the spongy electrode well-suited for long-term recording of high quality biopotential signals including electrocardiogram (ECG) and electromyography (EMG) on ambulatory patients. As a demonstration of its clinical usage with a focus on maternal and fetal health monitoring, I will show an array of such soft electrodes integrated on a printed patch of textile-based interconnections, and used for recording and spatiotemporal mapping of the uterine contraction patterns from patients in active labor.

Flexible Sponge‐Based Nanogenerator for Energy Harvesting from Land and Water Transportation

AbstractTriboelectric nanogenerator (TENG) devices with high robustness are promising in collecting powerful energy. In this study, highly elastic and pressure‐resistance sponge fabricated TENG capable of adapting to high strength impact in land and water transportation and scalable for any shape is demonstrated for harvesting wave energy and mechanical energy. The polydimethylsiloxane sponge prepared by sacrificial template method has interconnected network and large size ratio of cavity‐wall suitable for contact and separation. The operation modes of self‐contact and extra‐contact collaborating with MXene in electron transfer provide options for different operating conditions. The polydopamine‐MXene modification of the sponge enables higher output due to the combination of the electronegativity, excellent adhesion, and antioxidant ability. Sponges are used to collect mechanical energy and applied for TENG‐powered cathodic protection, making the 304 stainless steel (304 SS, Φ = 2 mm) electrode enter a thermodynamic stable state. What's more, the work also tries the universal strategies of program monitoring wave in the water tank and harvests the mechanical energy created by cars and passers‐by, which enrich the applications of sponge TENG.

Easily operated COF-based monolithic sponges as matrix clean-up materials for non-targeted analysis of chemical hazards in oil-rich foods

Non-targeted analysis of chemical hazards in foods plays a crucial role in controlling food safety. However, because it brings forward high demand for sample pretreatment, materials suitable for the pretreatment of foods, especially animal foods, are rare. Herein, covalent organic frameworks (COF)-based monolithic materials were constructed by three successive steps: preparation of polydimethylsiloxane (PDMS) sponge using sugar cube as a sacrificial template, loading of a heteroporous COF on PDMS sponge via ultrasonic or in-situ growth method, coating of the obtained PDMS@COF by polydopamine (PDA) network. As-prepared PDMS@COF@PDA sponges were demonstrated to work well in sample pretreatment of animal foods for non-targeted analysis of chemical hazards. After a simple vortex treatment for about 2 min, more than 98% triglycerides, the main interfering matrix components in animal foods, could be removed from lard and pork samples, accompanied by “full recovery” (recovery efficiencies: ≥63%) of 44 chemical hazards with different physicochemical properties. Besides providing promising sample pretreatment materials for non-targeted food safety analysis, this work also paves a feasible way to improve COF-based monolithic materials and thus promote their practical applications, because we found that the introduction of PDA network on COF-based monolithic material surface could play a role in “killing three birds with one stone”: enhancing the stability of the materials by overcoming the detachment of COF during operations; controllably adjusting hydrophobic and hydrogen-bonding interactions on the material surface to promote the removal of triglycerides; weakening the hydrophobic and π-π interactions between COF and chemical hazards to increase the recoveries of chemical hazards.

Self-powered pressure sensor for detecting static and dynamic stimuli through electrochemical reactions

As Internet of things (IoT) devices with pressure sensors become widely used, the need for lowering their power consumption increases. However, most pressure sensors require an additional power source to convert external stimuli into output signals. This study develops a self-powered pressure sensor (SPS) that measures both static and dynamic stimuli without an external power source. The SPS consists of two electrodes and a functional sponge with an electrolyte (water/glycerol/NaCl) and is based on an electrochemical reaction. The functional sponge is a hydrogel-coated polydimethylsiloxane (PDMS) sponge prepared by coating the surface of the PDMS sponge with a polyacrylamide (PAAM) hydrogel to contain the electrolyte. The SPS exhibits a sensitivity (10 kPa−1) and dynamic range (up to 110 kPa). The SPS is used on a self-powered safety alarm system to visually validate the pressure applied to the SPS. The SPSs are integrated into a glove to control an RC car using pressure applied to the SPSs on the fingertips. A thimble-type SPS is developed to measure the applied pressure and produce Morse code signals with static output signals. The SPS can be applied to wearable devices or robotics to measure pressure without an external energy source, reducing the system’s energy consumption.

Superhydrophobic/superoleophilic modified melamine sponge for oil/water separation

In this work, an environmentally friendly, superhydrophobic and durable modified melamine sponge was fabricated through a simple two-step dipping method. Through this strategy, the active carbon (AC) particles and reduced graphene oxide (rGO) were fixed on the melamine sponge skeleton with polydimethylsiloxane (PDMS) glue to form MS/rGO/AC/PDMS sponge, which has a multi-stage pore structure. Water contact angle (WCA) revealed that the as-prepared sponge possessed excellent water repellency up to 164°. Being applied in the field of oil/water separation, MS/rGO/AC/PDMS exhibited excellent oil-water selectivity, high oil sorption ability up to 120 g/g, and separation efficiency of over 99.85%. It is worth noting that under complex environments such as acid-base, fatigue and abrasion, the obtained sponge can maintain original properties, and the water contact angle exceeds 154°. In addition, it has good mechanical stability which can be reused and recovered continuously, making it a potential material for practical applications.

Piezoelectric composites from sandwiched polydimethylsiloxane sponges

A novel elastomer-based composite material with enhanced piezoelectric performances is proposed in this paper, which is composed of the top and bottom polytetrafluoroethylene (PTFE) solid films with the middle PTFE nanoparticle–polydimethylsiloxane (PDMS) sponge layer. To enhance the charge retention capability of elastomers, PTFE nanoparticles are introduced to form PTFE–PDMS interfaces, which can trap charges with longevity. Besides, PTFE solid films take on the role of the charge blocking layers to further improve the piezoelectric performances. As a result, the PTFE–PDMS sandwich structure shows the advantages of remarkable sensitivity (1053 pC/N), high stability, and flexibility. After a 6 h of annealing treatment at the temperature of 100 °C, no significant deterioration of the piezoelectric properties can be observed, which reveals the great thermal stability of the sandwich structure. In addition, the sandwich structure can be immersed in water for 24 h without any loss of piezoelectric activity. Finally, the experiment of lighting one LED by hand pressing successfully demonstrates that the sandwich structure has good applicability in the field of energy harvesting. Considering the excellent electrical and mechanical features, the PTFE–PDMS sandwich structure has promising applications in sensing, energy harvesting, and actuation.

Rational designed ZIF-8@PDA@PDMS composite sponge for efficient and sustainable particulate matter filtering under harsh environment

Particulate matter (PM) is a significant danger to both environment and human health. Despite the development of a series of air filters, they do not work well in harsh environment such as high temperature, high humidity or long-time filtration. To make a three-dimensional (3D) particle capture device, a sacrificial template approach was used to manufacture polydimethylsiloxane (PDMS) sponge, and then zeolite imidazole framework-8 (ZIF-8) was grown in situ on the 3D network of PDMS sponge. The removal efficiency of PM2.5 or PM10 is greater than 99.8% because of the high specific surface area and porous network structure of PDMS sponge, as well as the large number of metal sites of ZIF-8. In addition, the sponge filter has long-term filtration stability and still achieves excellent performance after 65 h of filtration. The composite sponge can adapt to harsh environments such as high temperature (250 °C) and high humidity (90% RH). Composite sponge filter has a regular shape, and it may be customized to any shape as required. This study provides a new idea for designing 3D high-efficiency air filters that can adapt to harsh environments.

Smart polydimethylsiloxane sponges with high piezoelectric responses

AbstractIn recent years, soft and stretchable electrets have drawn considerable attention for their wide applications in energy harvesters, sensors, and actuators. However, existing electrets struggle to attain both longevity and stretchability (softness), which means charge retention capability and stretchability (softness) of electrets conflict. In this article, one novel soft and stretchable electret (PPSE) with great electromechanical performance is demonstrated. The PPSE is composed of a polydimethylsiloxane (PDMS) sponge and polytetrafluoroethylene (PTFE) particles. The uniformly distributed pores obtained by the sugar leaching method inside the PPSE can not only accumulate macroscopic dipoles but also provide great stretchability, flexibility, and softness for the material. The resulting PPSE has a large value up to 477 pC/N and great charge stability. Moreover, by the virtue of stretchability and softness, it can output electric signals from twisting, bending, and other mechanical interactions without breaking apart. With these great performances, PPSE will potentially enable applications for actuation, sensing, and energy harvesting.

High-performance and superhydrophobic piezoresistive pressure sensor based on mountain ridge-like microstructure by silver nanoparticles and reduced graphene oxide

Ingenious microstructure design is crucial for piezoresistive pressure sensor to achieve excellent sensing performances and water repellency. Herein, we propose a new strategy to prepare high-performance polydimethylsiloxane (PDMS) sponge-based piezoresistive pressure sensor with superhydrophobicity. The silver nanoparticles and reduced graphene oxide on the skeleton surface of PDMS sponge jointly constructed mountain ridge-like microstructure and endowed the sensor with conductive network. The sensor exhibited high sensitivity, wide detection range, fast response and exceptional repeatability (4,000 loading–unloading cycles) and was applied for detecting human motions and daily scenarios. Owing to the hierarchical microstructure and the surface modification by 1H,1H,2H,2H-perfluorooctyltriethoxysilane, the sensor showed a high water contact angle of 156°, and the response signal kept stable even being sprayed by water. The prepared high-performance and superhydrophobic piezoresistive pressure sensor in this work has great potential in wearable electronics, healthcare monitoring and smart robot.