Aim To evaluate the interactive effects of different self- adhesive resin cements and tribochemical treatment on bond strength to zirconia. Methodology The following self-adhesive resin cements for bonding two zirconi...Aim To evaluate the interactive effects of different self- adhesive resin cements and tribochemical treatment on bond strength to zirconia. Methodology The following self-adhesive resin cements for bonding two zirconia blocks were evaluated： Maxcem （MA）, Smartcem （SM）, Rely X Unicem Aplicap （UN）, Breeze （BR）, Biscem （BI）, Set （SE）, and Clearfil SA luting （CL）. The specimens were grouped according to conditioning as follows： Group 1, polishing with 600 grit polishing paper; Group 2, silica coating with 110 μm Al2O3 particles which modified with silica; and, Group 3, tribochemical treatment - silica coating ＋ silanization. Specimens were stored in distilled water at 37℃ for 24 hours before testing shear bond strength. Results Silica coating and tribochemical treatment significantly increased the bond strength of the MA, UN, BR, B1, SE and CL to zirconia compared to #600 polishing. For both #600 polished and silica coating treatments, MDP- containing self-adhesive resin cement CL had the highest bond strengths to zirconia. Conclusion Applying silica coating and tribochemical treatment improved the bond strength of self-adhesive resin cement to zirconia, especially for CL.展开更多
With the advent of the 5G era and the rise of the Internet of Things,various sensors have received unprecedented attention,especially wearable and stretchable sensors in the healthcare field.Here,a stretchable,self-he...With the advent of the 5G era and the rise of the Internet of Things,various sensors have received unprecedented attention,especially wearable and stretchable sensors in the healthcare field.Here,a stretchable,self-healable,self-adhesive,and room-temperature oxygen sensor with excellent repeatability,a full concentration detection range(0-100%),low theoretical limit of detection(5.7 ppm),high sensitivity(0.2%/ppm),good linearity,excellent temperature,and humidity tolerances is fabricated by using polyacrylamide-chitosan(PAM-CS)double network(DN)organohydrogel as a novel transducing material.The PAM-CS DN organohydrogel is transformed from the PAM-CS composite hydrogel using a facile soaking and solvent replacement strategy.Compared with the pristine hydrogel,the DN organohydrogel displays greatly enhanced mechanical strength,moisture retention,freezing resistance,and sensitivity to oxygen.Notably,applying the tensile strain improves both the sensitivity and response speed of the organohydrogel-based oxygen sensor.Furthermore,the response to the same concentration of oxygen before and after self-healing is basically the same.Importantly,we propose an electrochemical reaction mechanism to explain the positive current shift of the oxygen sensor and corroborate this sensing mechanism through rationally designed experiments.The organohydrogel oxygen sensor is used to monitor human respiration in real-time,verifying the feasibility of its practical application.This work provides ideas for fabricating more stretchable,self-healable,self-adhesive,and high-performance gas sensors using ion-conducting organohydrogels.展开更多
A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethyls...A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethylsiloxane(PDMSOH).The condensation reaction between PAA and PDMS-OH has been confirmed by attenuated total reflection Fourier transform infrared(ATR-FTIR)spectra.The prepared PAA-PDMS elastomers possess robust mechanical strength and strong adhesiveness to human skin,and they have fast self-healing ability at room temperature(in^10 s with the efficiency of 98%).Specifically,strain sensors were fabricated by assembling PAA-PDMS as packaging layers and polyetherimide-reduced graphene oxide(PEI-rGO)as strain-sensing layers.The PAA-PDMS/PEI-rGO sensors are stably and reliably responsive to slight physical deformations,and they can be attached onto skin directly to monitor the body’s motions.Meanwhile,strain sensors can self-heal quickly and completely,and they can be reused for the motion detecting after shallowly scratching the surface.This work provides new opportunities to manufacture high performance self-adhesive and self-healing materials.展开更多
The effects of different post-space pretreatments on the retentive force of fiber posts cemented with a self-adhesive resin cement were investigated. Twenty-eight single-canal premolars were obturated by Resilon using...The effects of different post-space pretreatments on the retentive force of fiber posts cemented with a self-adhesive resin cement were investigated. Twenty-eight single-canal premolars were obturated by Resilon using warm vertical compaction and treated with distilled water, 2.5% NaOCl, 17% EDTA and 2.5% NaOCI; or 17% EDTA, 2.5% NaOCI, and ultrasonic agitation （U/E/N treatment）. Subsequently, radicular dentin surfaces were observed under scanning electron microscopy （SEM）. RelyX Fiber Posts were cemented in the treated canals by using RelyX U100, and thin-slice push-out test and SEM observation of coronal and apical regions of the specimens were performed. Data were analyzed using two-way ANOVA and Tukey＇s HSD post- hoc tests, and the percentage of failure type was calculated. Ultrasonic/EDTA/NaOC1 irrigation showed the maximum effectiveness in removing the smear layer and debris on the dentin surface. The apical bond strength of the experimental groups was significantly higher than that of the control group （P〈 0.05）. Adhesive failure between cement and dentin was the most common mode of failure. No obvious RDIZ or resin tag was detected. Chemical irrigants facilitated the bonding of these fiber posts, and ultrasonic activation improved retention. Future studies should evaluate the effectiveness of irrigation on fiber post push-out strength in fatigue cycling condition.展开更多
Angong Niuhuang pill, a Chinese materia medica preparation, can improve neurological func-tions after acute ischemic stroke. Because of its inconvenient application and toxic components （Cinnabaris andRealgar）, we u...Angong Niuhuang pill, a Chinese materia medica preparation, can improve neurological func-tions after acute ischemic stroke. Because of its inconvenient application and toxic components （Cinnabaris andRealgar）, we used transdermal enhancers to deliverAngong Niuhuang pill by modern technology, which expanded the safe dose range and clinical indications. In this study, Angong Niuhuang stickers administered at different point application doses （1.35, 2.7, and 5.4 g/kg） were administered to theDazhui （DU14）, Qihai（RN6） andMingmen （DU4） of rats with chronic cerebral ischemia, for 4 weeks. The Morris water maze was used to determine the learning and memory ability of rats. Hematoxylin-eosin staining and Nissl staining were used to observe neuronal damage of the cortex and hippocampal CA1 region in rats with chronic cerebral ischemia. The middle- and high-dose point application ofAngong Niuhuangstickers attenuated neuronal damage in the cortex and hippocampal CA1 region, and improved the memory of rats with chronic cerebral ischemia with an efifcacy similar to interventions by electroacupuncture at Dazhui （DU14）,Qihai （RN6） andMingmen （DU4）. Our experimental ifndings indicate that point application withAngong Niuhuang stickers can improve cognitive function after chronic cerebral ischemia in rats and is neuroprotective with an equivalent efifcacy to acupuncture.展开更多
In this study, we extracted and purified components in the Angong Niuhuang pill. Then we applied transdermal enhancers to Angong Niuhuang stickers by modern technology. The Angong Niuhuang sticker includes extracts fr...In this study, we extracted and purified components in the Angong Niuhuang pill. Then we applied transdermal enhancers to Angong Niuhuang stickers by modern technology. The Angong Niuhuang sticker includes extracts from curcuma, berberine hydrochloride, baicalin, geniposide, borneol, and musk. Angong Niuhuang stickers at different point application doses （1.35, 2.7, and 5.4 g/kg） were administered to Dazhui （DU14）, Qihai （RN6） and Mingmen （DU4）. Rats in the different dose point application and acupuncture groups were continuously administered for 7 days. Then a middle cerebral artery occlusion model was prepared for simulating human cerebral ischemia. Twelve hours later, expressions of Bcl-2, Bax and p53 protein in hippocampal CA1 were detected with immunohistochemistry. The expression level of Bcl-2, an anti-apoptotic protein, significantly increased in the high-, medium- and low-dose point application groups and the acupuncture group, while the expression of the pro-apoptotic proteins, Bax and p53, significantly decreased compared with the middle cerebral artery occlusion rats; and the Bcl-2/Bax ratio was significantly increased. The difference was noticeable for the high-dose point application group, which showed statistical difference compared with the low-dose point application group and the acupuncture group. Our experimental findings indicate that point application with Angong Niuhuang stickers promotes the expression of Bcl-2, and inhibits the expressions of Bax and p53 in the hippocampal CA1 area of rats after focal cerebral ischemia. Thus, point application of Angong Niuhang stickers protects brain tissues from cerebral ischemia.展开更多
Long-term biopotential monitoring requires high-performance biocompatible wearable dry electrodes.But currently,it is challenging to establish a form-preserving fit with the skin,resulting in high interface impedance ...Long-term biopotential monitoring requires high-performance biocompatible wearable dry electrodes.But currently,it is challenging to establish a form-preserving fit with the skin,resulting in high interface impedance and motion artifacts.This research aims to present an innovative solution using an all-green organic dry electrode that eliminates the aforementioned challenges.The dry electrode is prepared by introducing biocompatible maltitol into the chosen conductive polymer,poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate).Thanks to the secondary doping and plasticizer effect of maltitol,the dry electrode exhibits good stretchability(62%),strong self-adhesion(0.46 N/cm),high conductivity(102 S/cm),and low Young's modulus(7 MPa).It can always form a conformal contact with the skin even during body movements.Together with good electrical properties,the electrode enables a lower skin contact impedance compared to the current standard Ag/AgCl gel electrode.Consequently,the application of this dry electrode in bioelectrical signal measurement(electromyography,electrocardiography,electroencephalogra-phy)and long-term biopotential monitoring was successfully demonstrated.展开更多
In this paper, the sticker based DNA computing was used for solving the independent set problem. At first, solution space was constructed by using appropriate DNA memory complexes. We defined a new operation called “...In this paper, the sticker based DNA computing was used for solving the independent set problem. At first, solution space was constructed by using appropriate DNA memory complexes. We defined a new operation called “divide” and applied it in construction of solution space. Then, by application of a sticker based parallel algorithm using biological operations, independent set problem was resolved in polynomial time.展开更多
The complexity of application environment stimulates the development of wearable devices based on functional hydrogels.Among all the promising performances,self-healing and self-adhesion properties are ideal for hydro...The complexity of application environment stimulates the development of wearable devices based on functional hydrogels.Among all the promising performances,self-healing and self-adhesion properties are ideal for hydrogel sensors,which can guarantee good accuracy,comfort and long service life.However,it is still a challenge to achieve simultaneous self-healing and self-adhesion in different environments(in the air,underwater and at low temperatures).Herein,a feasible new strategy was successfully carried out to prepare a starch-based composite conductive organohydrogel based on the reversible borate ester bonds formed by complexing starch/polyvinyl alcohol(PVA)/tea polyphenol(TP)with borax,and multiple hydrogen-bond interactions among PVA,starch,TP and ethylene glycol(EG).Silver nanoparticles(Ag-NPs),reduced and stabilized by TP,and MWCNTs(multi-walled carbon nanotubes)were introduced into the cross-linking networks to endow the resulting PBSTCE organohydrogel with considerable antibacterial property and conductivity,respectively.The organohydrogel possessed rapid self-healing(HE(self-healing efficiency)=96.07%in 90 s,both in the air and underwater,also at-20℃),considerable self-adhesion(both in the air and underwater,also at-20℃),remarkable stretchability(814%of elongation),anti-freezing(-20℃)and moisture-retention abilities,antibacterial activity,sensitive pH/sugar-responsiveness,and plasticity.The strain sensor formed by the PBSTCE organohydrogel can not only effectively record large-scale human motions(e.g.finger/wrist/elbow bending,walking,etc.),but also accurately capture subtle motion changes(e.g.breathing,chewing,swallowing,speaking,smiling and frowning).Moreover,the self-healed organohydrogel sensor also exhibited almost invariable mechanical,electrical and sensing behaviors.This work demonstrates a feasible strategy to construct multifunctional starch-based organohy-drogels,and promotes their efficient,stable and eco-friendly application as flexible wearable devices.展开更多
文摘Aim To evaluate the interactive effects of different self- adhesive resin cements and tribochemical treatment on bond strength to zirconia. Methodology The following self-adhesive resin cements for bonding two zirconia blocks were evaluated： Maxcem （MA）, Smartcem （SM）, Rely X Unicem Aplicap （UN）, Breeze （BR）, Biscem （BI）, Set （SE）, and Clearfil SA luting （CL）. The specimens were grouped according to conditioning as follows： Group 1, polishing with 600 grit polishing paper; Group 2, silica coating with 110 μm Al2O3 particles which modified with silica; and, Group 3, tribochemical treatment - silica coating ＋ silanization. Specimens were stored in distilled water at 37℃ for 24 hours before testing shear bond strength. Results Silica coating and tribochemical treatment significantly increased the bond strength of the MA, UN, BR, B1, SE and CL to zirconia compared to #600 polishing. For both #600 polished and silica coating treatments, MDP- containing self-adhesive resin cement CL had the highest bond strengths to zirconia. Conclusion Applying silica coating and tribochemical treatment improved the bond strength of self-adhesive resin cement to zirconia, especially for CL.
基金support from the National Natural Science Foundation of China(61801525)the Guangdong Basic and Applied Basic Research Foundation(2020A1515010693)+1 种基金the Guangdong Natural Science Funds Grant(2018A030313400),the Science and Technology Program of Guangzhou(201904010456)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(2021qntd09).
文摘With the advent of the 5G era and the rise of the Internet of Things,various sensors have received unprecedented attention,especially wearable and stretchable sensors in the healthcare field.Here,a stretchable,self-healable,self-adhesive,and room-temperature oxygen sensor with excellent repeatability,a full concentration detection range(0-100%),low theoretical limit of detection(5.7 ppm),high sensitivity(0.2%/ppm),good linearity,excellent temperature,and humidity tolerances is fabricated by using polyacrylamide-chitosan(PAM-CS)double network(DN)organohydrogel as a novel transducing material.The PAM-CS DN organohydrogel is transformed from the PAM-CS composite hydrogel using a facile soaking and solvent replacement strategy.Compared with the pristine hydrogel,the DN organohydrogel displays greatly enhanced mechanical strength,moisture retention,freezing resistance,and sensitivity to oxygen.Notably,applying the tensile strain improves both the sensitivity and response speed of the organohydrogel-based oxygen sensor.Furthermore,the response to the same concentration of oxygen before and after self-healing is basically the same.Importantly,we propose an electrochemical reaction mechanism to explain the positive current shift of the oxygen sensor and corroborate this sensing mechanism through rationally designed experiments.The organohydrogel oxygen sensor is used to monitor human respiration in real-time,verifying the feasibility of its practical application.This work provides ideas for fabricating more stretchable,self-healable,self-adhesive,and high-performance gas sensors using ion-conducting organohydrogels.
基金supported by the National Science Funds for Excellent Young Scholars of China (Grant No. 61822106)National Science Funds for Creative Research Groups of China (Grant No. 61421002)+1 种基金Natural Science Foundation of China (Grant No. 61671115)Opening Project of State Key Laboratory of Polymer Materials Engineering (Sichuan University) (Grant No. sklpme 2018-4-28)
文摘A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethylsiloxane(PDMSOH).The condensation reaction between PAA and PDMS-OH has been confirmed by attenuated total reflection Fourier transform infrared(ATR-FTIR)spectra.The prepared PAA-PDMS elastomers possess robust mechanical strength and strong adhesiveness to human skin,and they have fast self-healing ability at room temperature(in^10 s with the efficiency of 98%).Specifically,strain sensors were fabricated by assembling PAA-PDMS as packaging layers and polyetherimide-reduced graphene oxide(PEI-rGO)as strain-sensing layers.The PAA-PDMS/PEI-rGO sensors are stably and reliably responsive to slight physical deformations,and they can be attached onto skin directly to monitor the body’s motions.Meanwhile,strain sensors can self-heal quickly and completely,and they can be reused for the motion detecting after shallowly scratching the surface.This work provides new opportunities to manufacture high performance self-adhesive and self-healing materials.
基金Funded by the National Natural Science Foundation of China(No.H1408)
文摘The effects of different post-space pretreatments on the retentive force of fiber posts cemented with a self-adhesive resin cement were investigated. Twenty-eight single-canal premolars were obturated by Resilon using warm vertical compaction and treated with distilled water, 2.5% NaOCl, 17% EDTA and 2.5% NaOCI; or 17% EDTA, 2.5% NaOCI, and ultrasonic agitation （U/E/N treatment）. Subsequently, radicular dentin surfaces were observed under scanning electron microscopy （SEM）. RelyX Fiber Posts were cemented in the treated canals by using RelyX U100, and thin-slice push-out test and SEM observation of coronal and apical regions of the specimens were performed. Data were analyzed using two-way ANOVA and Tukey＇s HSD post- hoc tests, and the percentage of failure type was calculated. Ultrasonic/EDTA/NaOC1 irrigation showed the maximum effectiveness in removing the smear layer and debris on the dentin surface. The apical bond strength of the experimental groups was significantly higher than that of the control group （P〈 0.05）. Adhesive failure between cement and dentin was the most common mode of failure. No obvious RDIZ or resin tag was detected. Chemical irrigants facilitated the bonding of these fiber posts, and ultrasonic activation improved retention. Future studies should evaluate the effectiveness of irrigation on fiber post push-out strength in fatigue cycling condition.
基金supported by the National Natural Science Foundation of China,No.81403458a grant from Cultivation Project Foundation for Youth Technological Talents of Southern Medical University,No.B1012015
文摘Angong Niuhuang pill, a Chinese materia medica preparation, can improve neurological func-tions after acute ischemic stroke. Because of its inconvenient application and toxic components （Cinnabaris andRealgar）, we used transdermal enhancers to deliverAngong Niuhuang pill by modern technology, which expanded the safe dose range and clinical indications. In this study, Angong Niuhuang stickers administered at different point application doses （1.35, 2.7, and 5.4 g/kg） were administered to theDazhui （DU14）, Qihai（RN6） andMingmen （DU4） of rats with chronic cerebral ischemia, for 4 weeks. The Morris water maze was used to determine the learning and memory ability of rats. Hematoxylin-eosin staining and Nissl staining were used to observe neuronal damage of the cortex and hippocampal CA1 region in rats with chronic cerebral ischemia. The middle- and high-dose point application ofAngong Niuhuangstickers attenuated neuronal damage in the cortex and hippocampal CA1 region, and improved the memory of rats with chronic cerebral ischemia with an efifcacy similar to interventions by electroacupuncture at Dazhui （DU14）,Qihai （RN6） andMingmen （DU4）. Our experimental ifndings indicate that point application withAngong Niuhuang stickers can improve cognitive function after chronic cerebral ischemia in rats and is neuroprotective with an equivalent efifcacy to acupuncture.
基金supported by the Research Project of Administration of TCM of Guangdong Province, No. 20111270
文摘In this study, we extracted and purified components in the Angong Niuhuang pill. Then we applied transdermal enhancers to Angong Niuhuang stickers by modern technology. The Angong Niuhuang sticker includes extracts from curcuma, berberine hydrochloride, baicalin, geniposide, borneol, and musk. Angong Niuhuang stickers at different point application doses （1.35, 2.7, and 5.4 g/kg） were administered to Dazhui （DU14）, Qihai （RN6） and Mingmen （DU4）. Rats in the different dose point application and acupuncture groups were continuously administered for 7 days. Then a middle cerebral artery occlusion model was prepared for simulating human cerebral ischemia. Twelve hours later, expressions of Bcl-2, Bax and p53 protein in hippocampal CA1 were detected with immunohistochemistry. The expression level of Bcl-2, an anti-apoptotic protein, significantly increased in the high-, medium- and low-dose point application groups and the acupuncture group, while the expression of the pro-apoptotic proteins, Bax and p53, significantly decreased compared with the middle cerebral artery occlusion rats; and the Bcl-2/Bax ratio was significantly increased. The difference was noticeable for the high-dose point application group, which showed statistical difference compared with the low-dose point application group and the acupuncture group. Our experimental findings indicate that point application with Angong Niuhuang stickers promotes the expression of Bcl-2, and inhibits the expressions of Bax and p53 in the hippocampal CA1 area of rats after focal cerebral ischemia. Thus, point application of Angong Niuhang stickers protects brain tissues from cerebral ischemia.
基金Chongqing Funds for Distinguished Young Scientists,Grant/Award Number:cstc2021jcyj-jqX0033Key Laboratory of Flexible Electronics of Zhejiang Province,Grant/Award Number:2022FE003+4 种基金Youth Talent Support Program of Chongqing,Grant/Award Numbers:CQYC2021059206,cstc2021ycjhbgzxm0334National Key Research and Development Program of China,Grant/Award Number:2022YFB3803300National Natural Science Foundation of China,Grant/Award Numbers:52203211,62074022Natural Science Foundation of Chongqing Municipality,Grant/Award Number:cstc2020jcyjmsxmX0851High-Level Medical Reserved Personnel Training Project of Chongqing,Grant/Award Number:2020GDRC019。
文摘Long-term biopotential monitoring requires high-performance biocompatible wearable dry electrodes.But currently,it is challenging to establish a form-preserving fit with the skin,resulting in high interface impedance and motion artifacts.This research aims to present an innovative solution using an all-green organic dry electrode that eliminates the aforementioned challenges.The dry electrode is prepared by introducing biocompatible maltitol into the chosen conductive polymer,poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate).Thanks to the secondary doping and plasticizer effect of maltitol,the dry electrode exhibits good stretchability(62%),strong self-adhesion(0.46 N/cm),high conductivity(102 S/cm),and low Young's modulus(7 MPa).It can always form a conformal contact with the skin even during body movements.Together with good electrical properties,the electrode enables a lower skin contact impedance compared to the current standard Ag/AgCl gel electrode.Consequently,the application of this dry electrode in bioelectrical signal measurement(electromyography,electrocardiography,electroencephalogra-phy)and long-term biopotential monitoring was successfully demonstrated.
文摘In this paper, the sticker based DNA computing was used for solving the independent set problem. At first, solution space was constructed by using appropriate DNA memory complexes. We defined a new operation called “divide” and applied it in construction of solution space. Then, by application of a sticker based parallel algorithm using biological operations, independent set problem was resolved in polynomial time.
基金This work is financed by the National Natural Science Founda-tion of China(No.21978180).We appreciate the valuable help of Dr.Jinwei Zhang from the College of Biomass Science and Engineering of Sichuan University and Hui Wang from the Analytical&Testing Center of Sichuan University.We thank eceshi(www.eceshi.com)for the great help in SEM analysis.
文摘The complexity of application environment stimulates the development of wearable devices based on functional hydrogels.Among all the promising performances,self-healing and self-adhesion properties are ideal for hydrogel sensors,which can guarantee good accuracy,comfort and long service life.However,it is still a challenge to achieve simultaneous self-healing and self-adhesion in different environments(in the air,underwater and at low temperatures).Herein,a feasible new strategy was successfully carried out to prepare a starch-based composite conductive organohydrogel based on the reversible borate ester bonds formed by complexing starch/polyvinyl alcohol(PVA)/tea polyphenol(TP)with borax,and multiple hydrogen-bond interactions among PVA,starch,TP and ethylene glycol(EG).Silver nanoparticles(Ag-NPs),reduced and stabilized by TP,and MWCNTs(multi-walled carbon nanotubes)were introduced into the cross-linking networks to endow the resulting PBSTCE organohydrogel with considerable antibacterial property and conductivity,respectively.The organohydrogel possessed rapid self-healing(HE(self-healing efficiency)=96.07%in 90 s,both in the air and underwater,also at-20℃),considerable self-adhesion(both in the air and underwater,also at-20℃),remarkable stretchability(814%of elongation),anti-freezing(-20℃)and moisture-retention abilities,antibacterial activity,sensitive pH/sugar-responsiveness,and plasticity.The strain sensor formed by the PBSTCE organohydrogel can not only effectively record large-scale human motions(e.g.finger/wrist/elbow bending,walking,etc.),but also accurately capture subtle motion changes(e.g.breathing,chewing,swallowing,speaking,smiling and frowning).Moreover,the self-healed organohydrogel sensor also exhibited almost invariable mechanical,electrical and sensing behaviors.This work demonstrates a feasible strategy to construct multifunctional starch-based organohy-drogels,and promotes their efficient,stable and eco-friendly application as flexible wearable devices.
