angular ui router nested state with params cannot load stylesheet

I'm still new to angular ui router and I have problem with nested state / nested views need your help. I have angular app using ui.router with the states definition as bellow:

$locationProvider.html5Mode(true);
    $stateProvider
       .state('root',{
           abstract:'true'
           views:{
                 'top@':{},
                 '@':{}
                 }
                 })
       .state('childone',{
           url:'/childone,
           parent:'root'
           views:{
                 'top':{ template:"top navigation bar"},
                  '':{template:"Main Navigation"}
                 }
            });

for the childone state, every thing work as expected until I add some params to this state like this :

...
.state('childone',{
   url:"/childone/:child_id",
   parent:"root",
   views:{
         'top@':{
                 template:"Top navigation with some styling in app.css"
                 }
          '@':{
                 template:"Main contain with style"
              }
         }
});

Now. If I navigate to this childone state using link (ui-sref=({child_id:'1232'})) the page will load all stylesheet and apply to elements ok. But if I refresh the state or go there directly using url, the page will be broken, no styles are apply to element that broke my view. I tried so many options and solution from here but nothing work for me so far. could someone point me out what I'm missing / wrong here please.

( I'm trying to build a MEAN stack app. )

Edit: this is my Node/express server side to serve static index.html file:

var express = require('express');
var app = express();
var server = require('http').Server(app);
var port = process.env.PORT||80;
var mongoose = require('mongoose');
//var passport = require('passport'); //will be used later
var bodyParser = require('body-parser');
var cookie = require('cookie-parser');
var path = require('path');
var session = require('express-session');
var dbconf = require('./app/config/db');
var flash = require('connect-flash');
var conf = require('./app/config/app');
mongoose.connect(dbconf.mongo);

/*middleware*/
app.use(cookie(conf.secret));
app.use(session({cookie: { maxAge: 60000 }}));
app.use(flash());
app.use(express.static(__dirname + '/public'));

app.use(bodyParser());
app.use(bodyParser.json({type: "application/vnd.api+json"}));
app.use(bodyParser.urlencoded({extended: true}));


app.get('*',function(req,res) {
    res.sendFile(path.join(__dirname, '/public/' + 'index.html'));
});

app.use(function(req,res) {
    res.status(404);
    res.send('The path not exist');
});

server.listen(port);
console.log('Http server on and serving at port ' + port);