Polymer solar cells (PSCs) based on the bulk heterojunction (BHJ) blend of a conjugated polymer donor and a fullerene acceptor have gained considerable attention as a cost-effi cient, fl exible, and portable energy source. [1][2][3] Considering the practical aspects of its commercialization, the inverted device structure of PSCs (I-PSCs), consisting of a BHJ photoactive layer between indium tin oxide (ITO) as a bottom cathode and a high work function (WF) metal (Ag or Au) as a top anode, is an advantageous approach due to its superior long-term stability and printability. [4][5][6] In this type of inverted device structure, an additional interfacial layer between the active layer and ITO electrode must be introduced to establish the device concept. The high WF of the bottom ITO cathode (approximately 4.8 eV) hampers the formation of an ohmic contact with the lowest unoccupied molecular orbital (LUMO) level of fullerene and makes the creation of a high built-in fi eld used to break the electrical symmetry of the device diffi cult. Thus, many researchers explored a variety of interfacial materials to shift and modify the energy level of the ITO cathode. [4][5][6][7][8][9][10][11][12][13][14][15][16] Inorganic metal oxides (MOs), such as titanium oxide (TiO x ) or zinc oxide (ZnO), have been widely used as interfacial materials due to their solution processability (via a sol-gel precursor and nano-particle solutions) and their electron selective properties, which originate from their conduction band edges (typically at approximately 4 eV) that correspond well with the LUMO level of fullerene and the deep valence bands at approximately 8 eV. [8][9][10][11][12] However, I-PSCs using MOs typically require a high annealing temperature (over 200 ° C) to achieve a crystallinity of the MO that is suffi ciently high to yield a high charge carrier mobility, [ 8 , 9 ] and these devices require a crucial post-UV treatment to enhance the device performance (typically referred to as a 'light-soaking' problem). [10][11][12] Because the high-temperature annealing process is incompatible with typical printing processes that use fl exible plastic substrates and the post-UV treatment causes a harmful photo-oxidation in the conjugated polymers, these processes should be eliminated to promote the practical use of I-PSCs.To circumvent the inherent weaknesses of the MO interlayers, polymer-based interfacial materials, such as conjugated polyelectrolytes (CPEs) and nonconjugated polyethylene oxide (PEO), have also been employed. These polymer-based interlayers alter the WF of ITO by forming extremely thin interfacial dipoles (typically 1-2 nm) and facilitate charge transport into the ITO electrode. [17][18][19][20] Becuase cationic CPEs have charged ionic pendant groups in their structures, they can induce signifi cantly stronger dipole moments than the neutral PEO, resulting in a higher device performance than that of the I-PSC using PEO. [ 19 ] However, because CPEs typically require a delicate and complicated synthesis procedure, nonc...

Hydroxyapatite is a biologically compatible material and a major component of dental enamel and bone tissue. Because of its biocompatibility and structural similarity to human teeth and the skeletal system, a number of dental studies have evaluated its application as a bone substitute or dental restorative material. This study was to evaluate the differences in bonding strength and resistance to demineralization between micro-hydroxyapatite and nano-hydroxyapatite added to self-cured resin-reinforced/modified glass ionomer cement. RelyX was used as the base glass ionomer cement material and for the control group. 10% micro-hydroxyapatite added glass ionomer cement was named experimental group 1, and 10% nano-hydroxyapatite added glass ionomer cement was named experimental group 2. Physical tests for ISO9917-1:2007 in each group was acceptable, except the setting time of nano-hydroxyapatite added glass ionomer cement, which exceeded maximum setting time. Bonding strength was greatest in nano-hydroxyapatite glass ionomer cement, and cohesive failure was common in all specimens. When fractured surface was observed under SEM, spherical particles were observed in experimental groups containing hydroxyapatite particles, and they were more prevalent in nano-HA added glass ionomer cement group than in micro-hydroxyapatite added group. Both experimental groups exhibited greater resistance to demineralization compared to the control group, and there was no significant difference between the experimental groups. Under SEM, nano-hydroxyapatite added glass ionomer cement exhibited increased resistance to demineralization compared to micro-hydroxyapatite added glass ionomer cement.

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The skin barrier effectively inhibits the penetration of substances; therefore, drug delivery, especially the delivery of drugs that are hydrophilic, through the skin, is challenging. Objectives: Physicians in the esthetic field now use the transdermal drug delivery system to attempt to deliver esthetic materials, such as hyaluronic acid and poly‐DL‐lactic acid into the skin. Conventionally, esthetic physicians manually injected these materials using needle syringes into the dermis layer. However, the injection is often irregular, imprecise, slow, and painful. Injector devices have been developed to overcome these limitations. A total of five Korean cadavers (that of three men and two women with a mean age of 69.2 years; range, 60–73 years) underwent laser injection. We used a device called Er:YAG LASER to create the pressure needed for microjet delivery to the skin of the cadaver. Discussion: In this study, the first LASER pressure‐based, needle‐free microjet injector was used to deliver drugs effectively into the dermis of a cadaver. This study showed that a novel needle‐free microjet injector using Er:YAG LASER can introduce beneficial, liquid, esthetic drugs into the papillary dermal layer (depth of 300um) with minimal epidermal damage.