Showing papers by "Hua Zhang published in 2004"
TL;DR: The Dip-Pen Nanolithography (DPN) is a direct-write tool for generating surface-patterned chemical functionality on the sub-100 nm length-scale as discussed by the authors.
Abstract: The ability to tailor the chemical composition and structure of a surface on the 1-100 nm length scale is important to researchers studying topics ranging from electronic conduction, to catalysis, to biological recognition in nanoscale systems. Dip-pen nanolithography (DPN) is a new scanning-probe based direct-write tool for generating such surface-patterned chemical functionality on the sub-100 nm length-scale, and it is a technique that is accessible to any researcher who can use an atomic force microscope. This article introduces DPN and reviews the rapid growth of the field of DPN-related research over the past few years. Topics covered range from the development of new classes of DPN-compatible chemistry, to experimental and theoretical advances in the understanding of the processes controlling tip-substrate ink transport, to the implementation of micro-electro-mechanical system (MEMS) based strategies for parallel DPN applications.
911 citations
TL;DR: The Dip-Pen Nanolithography (DPN) is a direct-write tool for generating surface-patterned chemical functionality on the sub-100 nm length-scale as mentioned in this paper.
Abstract: The ability to tailor the chemical composition and structure of a surface on the 1-100 nm length scale is important to researchers studying topics ranging from electronic conduction, to catalysis, to biological recognition in nanoscale systems. Dip-pen nanolithography (DPN) is a new scanning-probe based direct-write tool for generating such surface-patterned chemical functionality on the sub-100 nm length-scale, and it is a technique that is accessible to any researcher who can use an atomic force microscope. This article introduces DPN and reviews the rapid growth of the field of DPN-related research over the past few years. Topics covered range from the development of new classes of DPN-compatible chemistry, to experimental and theoretical advances in the understanding of the processes controlling tip-substrate ink transport, to the implementation of micro-electro-mechanical system (MEMS) based strategies for parallel DPN applications.
100 citations
TL;DR: In this article, the authors used dip-pen nanolithography (DPN) to generate resist layers on Au, Ag, and Pd that when combined with wet-chemical etching can lead to nanostructures with deliberately designed shapes and sizes.
Abstract: Dip-pen nanolithography (DPN) has been used to generate resist layers on Au, Ag, and Pd that when combined with wet-chemical etching can lead to nanostructures with deliberately designed shapes and sizes. Monolayers of mercaptohexadecanoic acid (MHA) or octadecanethiol (ODT), patterned by DPN, were explored as etch resists. They work comparably well on Au and Ag, but ODT is the superior material for Pd. MHA seems to attract the FeCl3 etchant and results in nonuniform etching of the underlying Pd substrate. Dots, lines, triangles, and circles, ranging in size from sub-100 to several hundred nanometers have been fabricated on Si/SiOx substrates. These results show how one can use DPN as an alternative to more complex and costly procedures such as electron beam lithography to generate nanostructures from inorganic materials.
99 citations
TL;DR: The Dip-Pen-Nanolithographie (DPN) as mentioned in this paper is eine neue Direktschreibmethode with einem Kraftfeldmikroskop zur Erzeugung einer strukturierten chemischen Funktionalitat auf einer Oberflache im sub-100nm-Bereich.
Abstract: Die Moglichkeit zur gezielten Manipulation der chemischen Zusammensetzung und Struktur einer Oberflache auf der Langenskala von 1 bis 100 nm ist von zentraler Bedeutung fur einen breiten Bereich der nanotechnologischen Forschung, angefangen mit Studien zur elektronischen Leitfahigkeit, uber die Katalyse hin zur biologischen Erkennung. Die Dip-Pen-Nanolithographie (DPN) ist eine neue Direktschreibmethode mit einem Kraftfeldmikroskop zur Erzeugung einer strukturierten chemischen Funktionalitat auf einer Oberflache im Sub-100-nm-Bereich. In diesem Aufsatz stellen wir das Prinzip der DPN vor und betrachten die Entwicklungen der letzten Jahre. Die Themen erstrecken sich von der Entwicklung neuer DPN-kompatibler Materialien uber experimentelle und theoretische Untersuchungen der Prozesse, die den Spitze-Substrat-Transport der Tinte steuern, bis hin zur Implementierung von mikroelektromechanischen Systemen (MEMs) fur DPN-Parallelanwendungen.
78 citations
TL;DR: In this article, a simple and novel method for fabricating poly(dimethylsiloxane) (PDMS)-coated dip pen nanolithography (DPN) stamp tips was developed.
Abstract: A simple and novel method for fabricating poly(dimethylsiloxane) (PDMS)-coated dip pen nanolithography (DPN) stamp tips was developed. These kinds of tips absorb chemicals (“inks”) easily and allow one to generate molecule-based patterns in a conventional DPN experiment. The generated patterns also can be imaged with the same DPN stamp tips. This method is a type of scanning probe contact printing but provides the ability to generate higher resolution structures than one can obtain with the conventional technique, which thus far has only enabled micron scale patterning. Sub-100 nm resolution patterning with 16-mercaptohexadecanoic acid (MHA) as an ink is demonstrated with these novel tips and is comparable to what one can obtain with a conventional ink-coated Si3N4 probe tip. Proof-of-concept is also demonstrated with 1-octadecanethiol (ODT), dendrimers and cystamine as inks.
63 citations
TL;DR: In this article, a new class of open-ended, cylindrical Au−Ag alloy nanostructures on a Si/SiOx surface were synthesized by depositing dot MHA features on Ag-coated Si and SiOx, followed by etching with ferri/ferrocyanide solution.
Abstract: Dip-pen nanolithography (DPN) in conjunction with wet chemical etching was used to synthesize a new class of open-ended, cylindrical Au−Ag alloy nanostructures on a Si/SiOx surface. Ag nanostructures were prepared by depositing dot MHA features on Ag-coated Si/SiOx, followed by etching with ferri/ferrocyanide solution. When these Ag nanostructures are reacted with HAuCl4, electroless plating of Au occurs on the sidewalls of the silver features along with concomitant oxidation of the Ag. This results in the formation of novel open-ended, cylindrical Au−Ag alloy nanostructures. Insight into the mechanism for this process is provided.
57 citations
TL;DR: Compounds 1 and 2 are novel ent-pimarane diterpenoids with an unprecedented 12alpha,16-epoxy group that were isolated from Siegesbeckia orientalis by spectral methods.
Abstract: Eight new ent-pimarane diterpenoids and diterpenoid glycosides, namely, ent-12α,16-epoxy-2β,15α,19-trihydroxypimar-8-ene (1), ent-12α,16-epoxy-2β,15α,19-trihydroxypimar-8(14)-ene (2), ent-2α,15,16,19-tetrahydroxypimar-8(14)-ene (3), ent-15-oxo-2β,16,19-trihydroxypimar-8(14)-ene (4), ent-2-oxo-15,16-dihydroxypimar-8(14)-en-16-O-β-glucopyranoside (5), ent-2-oxo-15,16,19-trihydroxypimar-8(14)-ene (6), ent-2-oxo-3β,15,16-trihydroxypimar-8(14)-en-3-O-β-glucopyranoside (7), and ent-2β,15,16,19-tetrahydroxypimar-8(14)-en-19-O-β-glucopyranoside (9), together with seven known diterpenes (8, 10−15) were isolated from Siegesbeckia orientalis. Compounds 1 and 2 are novel ent-pimarane diterpenoids with an unprecedented 12α,16-epoxy group. Their structures were established by spectral methods, especially 1D and 2D NMR spectral methods.
56 citations
Patent•
14 May 2004
TL;DR: In this paper, a method for fabricating scanning probe microscopy (SPM) probes is described, where the probe is fabricated by forming a structural layer on a substrate, wherein the substrate forms a cavity.
Abstract: A method for fabricating scanning probe microscopy (SPM) probes is disclosed. The probes are fabricated by forming a structural layer on a substrate, wherein the substrate forms a cavity. A sacrificial layer is located between the substrate and the structural layer. Upon forming the structural layer, the sacrificial layer is selectively removed, and the probe is then released from the substrate. The substrate may then later be reused to form additional probes. Additionally, a contact printing method using a scanning probe microscopy probe is also disclosed.
38 citations
TL;DR: In this paper, the nucleation and growth stimulated by an electron beam in amorphous GaAs was performed using a high-resolution electron microscopy, and the results showed that the crystallization was closely related to the current density of the electron beam.
12 citations
7 citations
Journal Article•
TL;DR: The primary outcome for patients with Mondini malformation are similar to those with normal cochlear structure following the multi-channel co chlear implantation, and the results have no significant difference in compare with normalcochlear group.
Abstract: OBJECTIVE To describe clinical experiences with multi-channel cochlear implantation in patients with Mondini malformation. METHODS Among 300 patients who received multi-channel cochlear implants from 1996 to 2002 in Beijing Tongren Hospital, 15 patients were diagnosed with Mondini malformation. A retrospective analysis was performed dealing with the surgical techniques, mapping and rehabilitations characteristics after surgery. 15 patients with normal cochlear structure are consider as control group. RESULTS Gusher is found more common than the normal cochlear implantation, most of them are serious. The electrodes are inserted in the "cochleostomy" in full length of 13 Patients, 2 pairs of electrodes remains outside of "cochleostomy" in 2 patients. No serious complications occurred after implantation. All patients have auditory sensations. The impedance of the electrodes, the T level, C level and the hearing threshold are similar with the normal cochlear implantation group. The results have no significant difference in compare with normal cochlear group(P > 0.05). CONCLUSION Multi-channel cochlear implantation could be performed safely in patients with Mondini malformation. The primary outcome for patients with Mondini malformation are similar to those with normal cochlear structure following the multi-channel cochlear implantation.
Journal Article•
27 Oct 2004
TL;DR: It is observed that eye location extracted from a human face is used to be used to compute his/her height to the ground and using it together with face recognition can increase the curacy of the access control.
Abstract: Access control has much attracted research interest recently. In this paper, we propose a method using human face and height as human trait to recognize a person. We observe that eye location extracted from a human face is sta-ble to be used to compute his/her height to the ground. Using it together with face recognition can increase the ac-curacy of the access control. We have implemented the method on a PC installed with a stereo camera. The design criteria, techniques, implementation details, and performance testing are presented. Keywords: 3D reconstruction, gradient descent method, biometric fusion, application.