Contact radius of stamps in reversible adhesion

A mechanics model is developed for the contact radius of stamps with pyramid tips in transfer printing.This is important to the realization of reversible control of adhesion,which has many important applications,such as climbing robots,medical tapes,and transfer printing of electronics.The contact radius is shown to scale linearly with the work of adhesion between the stamp and the contacting surface,and inversely with the plane-strain modulus of the stamp. It also depends on the cone angle and tip radius of the stamp,but is essentially independent of details of the tip geometry.

Highly Stretchable Shape Memory Self-Soldering Conductive Tape with Reversible Adhesion Switched by Temperature

With practical interest in the future applications of next-generation electronic devices,it is imperative to develop new conductive interconnecting materials appropriate for modern electronic devices to replace traditional rigid solder tin and silver paste of high melting temperature or corrosive solvent requirements.Herein,we design highly stretchable shape memory self-soldering conductive(SMSC)tape with reversible adhesion switched by temperature,which is composed of silver particles encapsulated by shape memory polymer.SMSC tape has perfect shape and conductivity memory property and anti-fatigue ability even under the strain of 90%.It also exhibits an initial conductivity of 2772 S cm^(−1) and a maximum tensile strain of~100%.The maximum conductivity could be increased to 5446 S cm^(−1) by decreasing the strain to 17%.Meanwhile,SMSC tape can easily realize a heating induced reversible strong-to-weak adhe-sion transition for self-soldering circuit.The combination of stable conductivity,excellent shape memory performance,and temperature-switching reversible adhesion enables SMSC tape to serve two functions of electrode and solder simultaneously.This provides a new way for conductive interconnecting materials to meet requirements of modern electronic devices in the future.

Bioinspired Injectable Self-Healing Hydrogel Sealant with Fault-Tolerant and Repeated Thermo-Responsive Adhesion for Sutureless Post-Wound-Closure and Wound Healing

Hydrogels with multifunctionalities,including sufficient bonding strength,injectability and self-healing capacity,responsive-adhesive ability,fault-tolerant and repeated tissue adhesion,are urgently demanded for invasive wound closure and wound healing.Motivated by the adhesive mechanism of mussel and brown algae,bioinspired dynamic bonds cross-linked multifunctional hydrogel adhesive is designed based on sodium alginate(SA),gelatin(GT)and protocatechualdehyde,with ferric ions added,for sutureless post-wound-closure.The dynamic hydrogel cross-linked through Schiff base bond,catechol-Fe coordinate bond and the strong interaction between GT with temperature-dependent phase transition and SA,endows the resulting hydrogel with sufficient mechanical and adhesive strength for efficient wound closure,injectability and self-healing capacity,and repeated closure of reopened wounds.Moreover,the temperature-dependent adhesive properties endowed mispositioning hydrogel to be removed/repositioned,which is conducive for the fault-tolerant adhesion of the hydrogel adhesives during surgery.Besides,the hydrogels present good biocompatibility,near-infrared-assisted photothermal antibacterial activity,antioxidation and repeated thermo-responsive reversible adhesion and good hemostatic effect.The in vivo incision closure evaluation demonstrated their capability to promote the post-wound-closure and wound healing of the incisions,indicating that the developed reversible adhesive hydrogel dressing could serve as versatile tissue sealant.

A thermal actuated switchable dry adhesive with high reversibility for transfer printing

Transfer printing based on switchable adhesive that heterogeneously integrates materials is essential to develop novel electronic systems,such as flexible electronics and micro LED displays.Here,we report a robust design of a thermal actuated switchable dry adhesive,which features a stiff sphere embedded in a thermally responsive shape memory polymer(SMP)substrate and encapsulated by an elastomeric membrane.This construct bypasses the unfavorable micro-and nano-fabrication processes and yields an adhesion switchability of over1000 by combining the peel-rate dependent effect of the elastomeric membrane and the thermal actuation of the sub-surface embedded stiff sphere.Experimental and numerical studies reveal the underlying thermal actuated mechanism and provide insights into the design and operation of the switchable adhesive.Demonstrations of this concept in stamps for transfer printing of fragile objects,such as silicon wafers,silicon chips,and inorganic micro-LED chips,onto challenging non-adhesive surfaces illustrate its potential in heterogeneous material integration applications,such as flexible electronics manufacturing and deterministic assembly.

玻璃表面化学蚀刻增强基板上类金刚石薄膜的结合力与透光率

本研究采用一种新方法来改善类金刚石(DLC)薄膜在玻璃表面结合力弱的问题。首先通过反胶束微乳液刻蚀法在玻璃表面蚀刻出致密连续的微米凹坑,然后采用磁控溅射依次镀制SiO_(2)、SiOC过渡膜及DLC膜。由于薄膜物质嵌在连续的微米凹坑里形成波浪状的3D膜层,不仅可将应用在膜上的作用力分解释放,而且也大大提高了玻璃表面与膜的接触面积,从而显著增强DLC薄膜在玻璃表面的结合。为了改善薄膜在可见光区的透光性能,镀膜前,在玻璃球形凹坑的玻璃表面进行二次化学蚀刻,在凹坑里生成纳米孔结构,减少反射,提高可见光透过率。本研究采用紫外-可见分光光度计、扫描电镜、拉曼光谱仪、纳米力学综合测试系统、显微硬度仪及铅笔硬度测试等手段对样品进行了性能表征。结果表明,SiO_(2)、SiOC过渡层可以使玻璃基板与DLC薄膜之间结合力,从(28.82±0.62)mN提高到(53.32±0.78)mN,提高近1倍。在相同的DLC膜镀制条件下,玻璃表面的微米凹坑可进一步使DLC的膜基结合力再提高1倍,从(53.32±0.78)mN提高到(106.32±0.82)mN。显微硬度从543.7 HV提高到735.5 HV,铅笔硬度从6 H提高到7 H。通过二次化学蚀刻产生的纳米孔可使镀膜玻璃的可见光平均透过率提高约4%。

可光致固液转变偶氮苯染料的合成及其光控可逆黏合性能

光控可逆胶黏剂在特定波长的光照射下可以改变其黏接性质,实现高效的黏合与分离,并可多次重复利用。试验设计合成了一种含单个偶氮苯单元的小分子化合物D-Azo,探究了其光致固液转化及光控可逆黏合性能。紫外光照射前后的紫外-可见吸收光谱、氢核磁共振谱(1H NMR)及示差热量扫描(DSC)表明,在紫外光的作用下,D-Azo分子发生了异构转变,在光诱导下染料由固态快速转化为液态,且具有良好的循环稳定性,能够在多个光照周期中保持稳定的光响应性能。将D-Azo用于光控可逆黏合,D-Azo黏接的PMMA板承重达30~35 kg,黏附强度为0.80~0.93 MPa。D-Azo分子具有明显的光致固液转化特性,紫外光照射可以使其脱黏合,表明作为胶黏剂的可逆性和重复使用性能。该材料可望在纺织复合材料黏合领域以及可穿戴黏合材料等领域获得应用。

表达外源基因SPAM1重组CAV-2溶瘤病毒的构建与拯救

旨在研究犬腺病毒-2型(canine adenovirus type 2,CAV-2)作为溶瘤病毒的潜力并进一步探索精子黏附因子(SPAM1)协同CAV-2重塑肿瘤微环境在肿瘤免疫治疗中的应用价值。本研究以P15A-CAV-2反向遗传操作平台为基础,使用RED/ET同源重组系统构建携带SPAM1外源基因的中间载体,使用中间载体将CAV-2骨架载体E3区域缺失并替换SPAM1外源基因表达盒。再利用合成引物敲除kmccdB反向筛选表达盒构建P15A-CAV-2-mCMV-SPAM1-SV40 polyA感染性克隆质粒并在MDCK-E1A细胞系中拯救重组溶瘤病毒,对重组病毒体外溶瘤效应进行验证。根据测序与酶切验证结果证明,本研究成功构建并拯救出稳定表达外源基因SPAM1的重组溶瘤病毒1株;IFA试验证明,重组毒株能够高水平稳定表达外源基因且外源蛋白具有可弥散分布于细胞间的特点。缺失E3区域表达外源基因SPAM1的重组溶瘤病毒通过光镜观察和CCK8检测发现具有对犬癌细胞系A72强烈的杀伤效应。综上,本研究成功构建1株具有良好溶瘤效应的重组CAV-2,为后续应用于宠物肿瘤治疗奠定了基础。

反渗透自粘防水卷材对高层医院建筑工程的应用研究

为了验证自粘效果提升施工效率与质量,研究环保型反渗透自粘防水卷材对高层医院建筑工程的影响。使用多种高分子材料制备主体层,树脂与粘接材料制备出粘胶层,压制主体层和粘胶层,制备出应用在高层医院建筑工程的环保型反渗透自粘防水卷材。测试该卷材不同粘接方法以及不同温度环境下的剥离强度,计算静水环境和压力水环境该卷材的反渗透性,接种菌株分析该卷材的抗霉腐性能。结果显示,上下涂覆粘胶层的卷材剥离强度更高,但是高温环境会降低剥离强度;该卷材在高压水环境会比静水环境反渗透性差,但是显著高于目前市售普通卷材。

Complex coacervate-derived hydrogel with asymmetric and reversible wet bioadhesion for preventing UV light-induced morbidities

Protecting the skin from UV light irradiation in wet and underwater environments is challenging due to the weak adhesion of existing sunscreen materials but highly desired.Herein we report a polyethyleneimine/thioctic acid/titanium dioxide(PEI/TA/TiO_(2))coacervate-derived hydrogel with robust,asymmetric,and reversible wet bioadhesion and effective UV-light-shielding ability.The PEI/TA/TiO_(2)complex coacervate can be easily obtained by mixing a PEI solution and TA/TiO_(2)powder.The fluid PEI/TA/TiO_(2)coacervate deposited on wet skin can spread into surface irregularities and subsequently transform into a hydrogel with increased cohesion,thereby establishing interdigitated contact and adhesion between the bottom surface and skin.Meanwhile,the functional groups between the skin and hydrogel can form physical interactions to further enhance bioadhesion,whereas the limited movement of amine and carboxyl groups on the top hydrogel surface leads to low adhesion.Therefore,the coacervate-derived hydrogel exhibits asymmetric adhesiveness on the bottom and top surfaces.Moreover,the PEI/TA/TiO_(2)hydrogel formed on the skin could be easily removed using a NaHCO3 aqueous solution without inflicting damage.More importantly,the PEI/TA/TiO_(2)hydrogel can function as an effective sunscreen to block UV light and prevent UV-induced MMP-9 overexpression,inflammation,and DNA damage in animal skin.The advantages of PEI/TA/TiO_(2)coacervate-derived hydrogels include robust,asymmetric,and reversible wet bioadhesion,effective UV light-shielding ability,excellent biocompatibility,and easy preparation and usage,making them a promising bioadhesive to protect the skin from UV light-associated damage in wet and underwater environments.

A strong and reversible adhesive fibrillar surface based on an advanced composite with high strength and strong adhesion

A material-structure integrated design method is proposed in this paper,with which micropillar and microwedge arrayed surfaces are fabricated based on a novel nanoparticlereinforced silicone rubber composite(NRSRC)with high mechanical strength and strong surface adhesion.It is found that the micropillar-arrayed surface and the microwedgearrayed surface show a normal adhesive strength of 50.9 kPa and a shear adhesive strength of 137.3 kPa,respectively,which are much higher than those of previously reported adhesive surfaces made by pure soft polymers.Furthermore,the micro-wedgearrayed surface shows not only strong and stable adhe-sion on rough and smooth substrates but also an obvious anisotropy in the adhesion property.The latter consequently leads to an easy control of the attachment/detachment switch,which is evidenced by a mechanical gripper with a microwedged surface.Therefore,firmly picking up and easily releasing a heavy glass plate can be realized.All these results demonstrate the apparent advantages of the present compo-sitebased fibrillar surfaces in achieving reliable and reversible adhesion and should have promising applications for manufac-turing advanced adhesive devices,such as mechanical fixtures,portable climbing equipment and space robots.

富水环境下引水隧洞二次衬砌防水技术创新

富水隧洞施工过程中的防水施工技术很大程度上决定了隧洞建设项目的效果,如果施工中出现二衬混凝土脱落、裂缝,或者止水带平直度很差,都会导致隧洞渗漏水,为工程运行带来不利影响。本文结合吉林中部城市引松供水工程隧洞施工实例,分析了二次衬砌拱部纵向退管带模注浆工艺、自粘反粘式防水板、新型止水带夹具等新工艺、新技术在解决隧洞二衬裂缝、渗水、漏水、脱空、止水带平直度差等常见工程问题上的作用。

Laparoscopic vs open surgery in ileostomy reversal in Crohn’s disease:A retrospective study

BACKGROUND Although minimally invasive surgery is becoming more commonly applied for ileostomy reversal(IR),there have been relatively few studies of IR for patients with Crohn's disease(CD).It is therefore important to evaluate the potential benefits and risks of laparoscopy for patients with CD.AIM To compare the safety,feasibility,and short-term and long-term outcomes of laparoscopic IR(LIR)vs open IR(OIR)for the treatment of CD.METHODS The baseline characteristics,operative data,and short-term(30-d)and long-term outcomes of patients with CD who underwent LIR and OIR at our institution between January 2017 and January 2020 were retrieved from an electronic database and retrospectively reviewed.RESULTS Of the 60 patients enrolled in this study,LIR was performed for 48 and OIR for 12.There were no statistically significant differences in baseline characteristics,operation time,intraoperative blood loss,days to flatus and soft diet,postoperative complications,hospitalization time,readmission rate within 30 d,length of hospitalization,hospitalization costs,or reoperation rate after IR between the two groups.However,patients in the LIR group more frequently required lysis of adhesions as compared to those in the OIR group(87.5%vs 41.7%,respectively,P<0.05).Notably,following exclusion of patients who underwent enterectomy plus IR,OIR was more advantageous in terms of postoperative recovery of gastrointestinal function and hospitalization costs.CONCLUSION The safety and feasibility of LIR for the treatment of CD are comparable to those of OIR with no increase in intraoperative or postoperative complications.

以癫痫发作为首要症状的可逆性胼胝体压部病变综合征患儿临床特征及预后影响因素分析

目的 探讨以癫痫发作为首要症状的可逆性胼胝体压部病变综合征(RESLES)患儿临床特征及预后影响因素。方法 选取2016年1月—2021年12月收治的以癫痫发作为首要症状的RESLES患儿143例,统计分析其临床特征和预后情况,根据预后情况将其分为预后不良组(35例)和预后良好组(108例),探讨其预后影响因素,构建Nomogram预测模型,并采用受试者工作特征(ROC)曲线和决策曲线(DCA)验证该模型对以癫痫发作为首要症状RESLES患儿预后不良的预测价值和临床效用。结果 143例中表现为惊厥发作者占86.71%(124/143);有前驱感染症状者占89.51%(128/143);头颅MRI检查T1WI低或稍低信号者占91.61%(131/143),DWI高或稍高、FLAIR高或稍高、T2WI高或稍高者均达100.00%(143/143),孤立胼胝体压部病变者占81.82%(117/143),病变形状斑片形占51.05%(73/143)。合并胼胝体其他部位病变、意识障碍、心肌型肌酸激酶同工酶(CK-MB)、胶质纤维酸性蛋白(GFAP)、β-肌动蛋白(β-actin)、细胞间黏附分子-1(ICAM-1)是以癫痫发作为首要症状RESLES患儿预后不良的危险因素(P<0.01)。ROC曲线分析显示Nomogram预测模型预测以癫痫发作为首要症状的RESLES患儿预后不良的曲线下面积为0.909,95%CI 0.849,0.951,DAC显示该模型具有良好的临床效用。结论 以癫痫发作为首要症状的RESLES患儿以惊厥发作及前驱感染症状为主要表现,头颅MRI检查T1WI呈低或稍低信号,DWI、FLAIR、T2WI呈高或稍高信号,合并胼胝体其他部位病变、意识障碍、CK-MB、GFAP、β-actin、ICAM-1是其预后不良影响因素,构建Nomogram预测模型有助于筛选其预后不良高危人群。

拉扭耦合作用下柱形纤维与基底的界面黏附性能研究

受壁虎刚毛可逆黏附性能的启发,本文建立了单根弹性圆柱纤维与刚性基底黏附接触的理论和数值模型,同时考虑了拉伸和扭转载荷的耦合作用及纤维半径对界面黏附性能的影响.研究发现耦合载荷作用下柱形纤维同样存在一个临界半径,当纤维半径小于该临界尺寸时,界面应力达到均匀的理论强度分布,接触边界应力集中消失,出现缺陷不敏感现象;当纤维半径大于该临界尺寸时,界面以裂纹扩展而失效.在耦合载荷作用下纤维的临界半径小于纯拉伸而大于纯扭转时的临界尺寸,且该临界半径随着施加扭转载荷的增大而减小.表明在纯拉伸载荷下使界面黏附强度达到最优的柱形纤维,在拉伸和扭转载荷耦合作用下,由于界面失效形式的转变使界面易发生脱黏,并且界面脱黏时的拉脱力随着扭转载荷的增大而减小,理论和数值结果一致.本文结果进一步应用揭示了壁虎可以通过调控施加在其最小黏附单元上的载荷形式实现纯拉伸载荷下强黏附及耦合载荷下易脱黏的力学机制.

Robust scalable reversible strong adhesion by gecko-inspired composite design

Bio-inspired reversible adhesion has significant potential in many fields requiring flexible grasping and manipulation,such as precision manufacturing,flexible electronics,and intelligent robotics.Despite extensive efforts for adhesive synthesis with a high adhesion strength at the interface,an effective strategy to actively tune the adhesion capacity between a strong attachment and an easy detachment spanning a wide range of scales has been lagged.Herein,we report a novel soft-hard-soft sandwiched composite design to achieve a stable,repeatable,and reversible strong adhesion with an easily scalable performance for a large area ranging from~1.5 to 150 cm2 and a high load ranging from~20 to 700 N.Theoretical studies indicate that this design can enhance the uniform loading for attachment by restraining the lateral shrinkage in the natural state,while facilitate a flexible peeling for detachment by causing stress concentration in the bending state,yielding an adhesion switching ratio of~54 and a switching time of less than~0.2 s.This design is further integrated into versatile grippers,climbing robots,and human climbing grippers,demonstrating its robust scalability for a reversible strong adhesion.This biomimetic design bridges microscopic interfacial interactions with macroscopic controllable applications,providing a universal and feasible paradigm for adhesion design and control.

肝衰竭患者外周血单个核细胞hTERT mRNA及血清Ang-2和ICAM-1水平临床意义探讨

目的初步探讨肝衰竭患者外周血单个核细胞人瑞粒酶逆转录酶(hTERT)mRNA及血清血管生成素-2(Ang-2)和细胞间黏附分子-1(ICAM-1)水平变化的临床意义。方法2019年1月~2021年5月我院诊治的74例肝衰竭患者【亚急性肝衰竭(SALF)13例,慢加急性肝衰竭(ACLF)39例和慢性肝衰竭(CLF)22例】和同期健康体检者30例,分离并检测外周血单个核细胞(PBMC)hTERT mRNA水平,采用ELISA法检测血清Ang-2和ICAM-1水平。结果肝衰竭组PBMC hTERT mRNA、血清Ang-2和ICAM-1水平分别为(0.9±0.3)、(1344.6±55.3)ng/L和(540.2±22.4)ng/ml,显著高于健康人组【分别为(0.4±0.1)、(1062.5±36.2)ng/L和(167.3±15.6)ng/ml,P<0.05】;SALF患者PBMC hTERT mRNA、血清Ang-2和ICAM-1水平分别为(1.5±0.6)、(1507.8±38.2)ng/L和(647.3±26.2)ng/ml,显著高于ACLF患者【分别为(1.2±0.4)、(1398.6±35.8)ng/L和(582.7±24.1)ng/ml,P<0.05】或CLF患者【分别为(0.7±0.2)、(1280.5±46.3)ng/L和(468.9±20.3)ng/m,P<0.05】;经过1~3 m治疗,SALF组死亡3例,ACLF组死亡5例,CLF组死亡4例。结论肝衰竭患者PBMCs hTERT mRNA及血清Ang-2和ICAM-1水平显著升高,它们可能为判断肝损伤程度提供客观依据,值得进一步研究。

氨基三亚甲基膦酸对氟磷灰石和白云石选择性抑制机理研究

钙镁质磷矿反浮选过程中,氟磷灰石的选择性抑制是实现高效浮选分离的前提。通过单矿物浮选试验、FTIR分析、XPS测试、Zeta电位测试和气泡-颗粒黏附动力学(BPWA)测试等手段,研究了氨基三亚甲基膦酸(ATMP)对氟磷灰石和白云石浮选行为的影响及其选择性抑制机理,结果表明:ATMP会抑制氟磷灰石上浮,但对白云石的抑制作用有限;ATMP在氟磷灰石表面的吸附作用大于白云石,更倾向于选择吸附在氟磷灰石表面;ATMP主要与氟磷灰石表面的Ca原子作用,表现为化学吸附,占据Ca位点后降低了油酸钠(NaOL)的吸附作用,导致氟磷灰石被抑制,可浮性降低。

广东南粤银行广州金融大厦地下室底板双层TPO卷材防水技术探讨

广东南粤银行广州金融大厦项目地下室底板防水设计采用双层TPO高分子预铺反粘防水卷材预铺法施工,胶面自粘防水卷材与砂面预铺卷材形成满粘层,整体砂层与结构预铺反粘,并对桩头、底板后浇带、甩槎与接槎等部位防水做了处理。应用效果表明,该做法对新规下的防水要求适应性良好,可有效保障项目在复杂地下环境中的防水质量。

高分子自粘胶膜防水卷材在底板工程中的应用

以某会议中心工程为例,介绍了高分子自粘胶膜防水卷材在地下室底板防水工程中的应用,并对桩头、后浇带等细部节点做法,以及侧墙采用不同防水材料时底板预铺反粘卷材与侧墙卷材搭接的处理方法进行了阐述。

光致相变型偶氮苯基共聚物的制备及在可逆胶黏剂领域的应用

光致可逆胶黏剂的设计和开发,在一定程度上解决了传统胶黏剂在分离、回收和修复粘接表面等方面存在的问题。文中设计并合成了一种具有光致相态转换性能的偶氮苯基共聚物(PNY-Azo),其反式构象(固态)和顺式构象(液态)在黏附强度上表现出较大差异,实现了对黏附基材的光控黏附和剥离,可应用于制备光致可逆胶黏剂。通过在共聚物侧链上增加氧原子数量,以此增强了共聚物分子链间的超分子作用(氢键作用)以及共聚物的链间缠结性能,从而有效地提高了PNY-Azo的黏结强度,其反式构象状态下黏结强度最高可达4.59 MPa。